case study on campus design

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IED students and CampusX envision Gen Z student housing

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Design Process of a Campus Plan: A Case Study of Duzce University Konuralp Campus

Humanity have always felt the need to alter the environment they inhabit. In our modern era, this desire continues to exhibit itself in more urban landscapes. As a microcosm of the cityscape, university campuses contribute many cultural and economic advantages to the urban population. Moreover they bring under control to the urban growth and generally provides open and green spaces to the city. In this paper, Düzce University Konuralp Campus, located north of the Düzce City, was considered as our study area. Here we describe the Konuralp campus design which was developed in "Duzce University Konuralp Campus Development Plan Urban Design Competition". The method of the study consist of three steps. Some analyses like location, topography (ecological wind corridors and the meeting point of the valleys), spatial zoning, design axes and circulation were performed at the first step. In the second step it has been tried to specify how to apply the steps for designing kind of these campus projects. The concept of the design was created and constructed for the project. In the last step the design was visualized with 3D aplications and presented here. The aim of the study is how to design a campus which is sustainable and accessible. Consequently, the campus design was realized which had some design principles based on pedestrian priority. Educational buildings were separated from social buildings, sports center and cultural centers by using a-pedestrian walkways. In the middle of the working area campus square was designed which contains some land uses such as ceremony area, student center, amphitheatre and library. Finally a sustainable and accessible campus design was developed for Duzce University.

Related Papers

Sedef OZCELIK , Cahide Aydın İpekçi

The Cayirova Campus Settlement of Gebze Institute of Technology (GYTE) consists of three main areas where their connections are mostly isolated: (i) the area including administrative buildings and the school of architecture (ii) the area located between the railway and the seashore , (iii) the area where the buildings left from the Seed Certification Institute. The second year Architectural Design Studio has searched for proposals in order to build relations using the potentials of those areas such as railway/highway connections, the creek, the wood and seashore. There is evidence that the number of students using the campus is growing due to the increases in the acceptance of students in the recent years; and facilities are not adequate for the increasing demands. The absence/inadequacy of these facilities such as central library, dormitories and other accommodation, gathering spaces, student centre, arts & exhibition centre; lead to abundance impression when the common working hours in the campus end. This work aims to present the proposals of students who took part in this design studio. The study is conducted during the 2009-2010 Spring Semester for 14 weeks. Two tutors, one assistant tutor and 10 students attended to the studies. The project topic is presented by informing students about the integration of three main parts of the campus. Then the students are asked to develop proposals within two phases preceding each other. In the first phase, macro-scaled analysis for the particular areas of the campus is focused. The programs of proposals are formatted due to the other campus examples and students' own living experiences. Therefore, the program was not fixed and dictated, but was flexible and open to findings by the students. Students focused on integration of the neighbourhoods surrounding the campus as well as those three main parts. Different approaches were used in order to make use of the potentials of the areas; such as transportation, water element, hierarchy of greenery, user profiles, usage periods and characters of public spaces. As the first phase ended, the students were asked to focus on one particular facility within their proposal. The second phase focused on micro-scaled design and architectural approach. For the proposals of selected facilities; accessibility and sustainability were the main focus in order to create solutions. In both phases; plan, section and facade proposals; as well as the 3D visualisations-modelling and models were used in order to develop the concept. In addition, short animations and weekly sketch exercises were made.

Regional Conference on Campus Sustainability (RCCS)

Mohammad Hussaini Wahab

Campuses today range from rural to urban, from single buildings to expansive complexes, and from community colleges to public and private institutions to major research universities. A campus is a city consisting of elements that are highly interdependent which emerging and embody an urbanism of opportunity and innovation. Their commitment to sustainability is critical to establishing new standards, developing ground breaking approaches and preparing future global citizens. Since university is addressing diversity and inclusiveness in many ways, it has obligation to provide services and educational value to the community without discrimination. The modality of life on campus can be affected by different approaches in campus planning based on a comparative research on campuses. Universal design is one of those approaches that need to be considered. Universal design (UD) lately has assumed growing importance as a new paradigm that aims at a holistic approach ranging in urban design and specially campuses. It extends beyond the issues of mere accessibility of buildings for people with disabilities and there is an enormous need to become an integrated part of policies and planning in all aspects of urban campuses. The seven principles of UD are discussed in this paper in order to articulate the full range of criteria for attaining universal design for numerous types of designs. This paper surveys UD in University of British Columbia's Vancouver Campus as a case study to enable it to take lessons from a Well-connected and accessible campus in terms of UD. Here the attempt is made to review UD approaches in urban campus planning to expand the UD concept for applying in campuses.

Khairul Hisyam Kamarudin

AIP Publishing LLC

Zeyad Abdulrazzaq

The interest in the design of the university campus and its outdoor spaces and their sustainability emerged as a new trend that enriches the link between university buildings and outdoor spaces, and on the other hand, between humans and their environment, providing an opportunity to contemplate nature. Thus, making the campus less consuming natural resources and enhancing safety and security while maintaining the same level of quality and efficiency in the performance of the campus for its function. In addition to achieving the design compatible with the environment to provide the requirements of the current generation and ensure the rights of future generations. As well as achieving a state of balance within the university environment in a way that serves the environmental, economic and social aspects more effectively. This is with the need to take into account the integration of outdoor spaces with buildings to achieve the system of sustainability. The study aimed to clarify the importance of sustainable outdoor spaces at the university campus and to highlight the most important requirements and criteria for achieving them. This by identifying the most important problems that impeded the achievement of sustainability and suggesting appropriate mechanisms for them. The study found to the monitoring of many problems of outdoor spaces affects the achievement of sustainability in terms of environmental, economic, and social aspects as a result of administrative negligence and poor planning. Moreover, not taking into account the environmental needs of sustainability, as well as most of the outdoor spaces, lack their complementary components. Furthermore, the scarcity of water for irrigation, the soil of the site not being suitable for many plants, the height of the groundwater, and the lack of service and maintenance operations. The study also showed the lack of gardens and green areas out of the total area of the study site.

Arts and Design Studies

Mansour Nikpour

Nowadays Universities are considered as one source of environmental pollution due to their population and different activities occur in universities’ campuses. A lot of energy and materials are consumed during teaching activities and research process in universities. Although some environmental protection strategies can be seen in some universities, but more sustainable approaches to reduce the negative impacts of those activities are neglected. Therefore, this paper reviews some strategies for achieving sustainable universities through economical, environmental and social aspects based on previous studies in terms of Planning, transportation, energy efficiency and indoor environment. Finding of this research can be used for designing future higher education spaces with sustainable approach. Keywords: Sustainable University, Planning, Transportation, Energy efficiency, Indoor environment

Ozgur Yerli , Haldun Müderrisoglu

The buildings in which state and city affairs are carried out, people come and go freely are called public buildings. Universities also hosting public spaces and public structures in this sense. Both management unit and protocol and bureaucracy centre and at the same time since almost it is a reception area entrance and surrounding area are important as main building. So the rector building is one of the remarkable structure of universities. The aim of this study is to provide an open and green area to the university campuses which have positive contribution to urban open and green space systems. For this reason in this study landscape design process of Duzce University Rector of the building's entrance and reception area are examined, how it followed a path, how fiction design is shaped over during putting forward landscape design of such an important structure is disclosed. In the scope of study field analysis and data collecting, preparation of program requirements, creation of the function diagram, preparation of application projects and the implementation of project sections was synthesized. Introduction Person is an active, social being who affects and changes the environment as much as he is influenced by the environment he lives in. When the cities inhabited by the human are considered together with the environment the phenomenon of urban design arises. The understanding of the relationship between the people and their environment is the main element of urban design [1]. The public space is one of the components that directs and gives meaning to urban design. The term of public in architecture can be used both for the structures and also for the functions in the urban areas. Parks, squares, streets are the open public spaces used by all the urban residents for all the time [2]. In another definition the public space is defined as the space which is open for the public [3]. The public buildings can be defined as constructions such as governorate and municipality where the administrative works of the city, state and the town are carried out, where the public servants do their works and which can be easily accessed by the people. In this sense, the universities are also included within the public buildings and public spaces. The residential areas of the universities are called " campus ". Campuses are areas where the educational

Kırklareli Üniversitesi Mimarlık Fakültesi Dergisi

Ekrem Çalişkan , Ekrem B A H A D I R Çalışkan

The social, residential, recreational, cultural, and sports activities provided within university campuses play a significant role in higher education. In Turkey, numerous universities have been established in the last 20 years, and construction continues within the planning criteria on the designated campuses, parallel to the education provided. Kırklareli University was founded in 2007 with a large campus area outside the city. Since its establishment, the Kayalı Campus has provided many buildings, infrastructure, and environmental construction, dependent on master plan design criteria and other conditions. Priority design principles include separating pedestrian and vehicular traffic, defining building areas functionally, and ensuring accessibility and balance in placing squares and open distribution areas. In this study, the Kayalı Campus, an example of a significant out-of-town campus plan, was evaluated as a case study, and its structural development was observed over time. Firstly, a literature review was presented on university campus design, followed by a design brief on Kırklareli University Campus design project completed in 2009. Satellite images taken from the start of construction to the present day were presented, and the development was evaluated based on the master plan. The change in the transportation and zoning framework defined by the campus plans' regulatory and guiding role was compared with the current construction. Thus, the feedback on the campus plan development process was revealed over a long period with development decisions, management, and budget inputs. This study can be used as a framework for evaluating the development of different campuses and supporting subsequent decision-making processes with advanced land-use analysis.

Dr-Faris AlZubaidy

This research aims to examine the role of campus structure in achieving a sustainable environment. The study was conducted on the main campus of Baghdad University- Iraq, as a case study. In order to fulfil its practical parts, the research adopted a mix of quantitative and qualitative methods including a questionnaire, in-depth interviews and observations as data collection techniques. Findings included some urban design characteristics as key indicators of this impact such as directness, permeability, traffic speed, compactness, campus size and car parks. Through its conclusions, the study contributes to addressing issues related to campus sustainability in Iraq and elsewhere in the world.

The university campus is one of the largest urban educational entities, as it combines buildings and open outdoor spaces, so it has a strong impact on society. At present and in light of the taking care to make campus less resource-intensive, while maintaining the same level of quality and efficiency in job performance. Therefore the goal of achieving sustainability in the design of the campus has become to overcome the negative effects affecting the environment resulting from the various activities that take place within the university. The integration of outdoor spaces and campus buildings makes the university environment understandable to the user and gives him a sense of safety, orientation, and beauty. So, this requires a sustainable design with a suitable function for the use of university personnel. This design has distinct environmental characteristics that achieve human comfort and rejuvenate its vitality. Furthermore, the sustainable design integrates with the campus buildings that contain it functionally, sensually, and environmentally. In order to increase the utilitarian and aesthetic value of the site. As well as creating beautiful and comfortable spaces for the senses that enhance social interaction and contribute to enriching the intellectual and spiritual experience and are positively reflected in the achievement aims of the university. The concept of campus sustainability is the optimal use of available and possibilities resources human, material, or natural effectively and in an environmentally, socially, and economically balanced manner. In addition to reducing energy consumption and environmental pollution to ensure the preservation of human health and the continuity of perpetuating these spaces without wasting the gains and rights of future generations. The problem of the research was the lack of interest in the components of a sustainable campus, which necessitated clarification of the importance of sustainability and ways to achieve it. This is done by identifying the problems that impede achieving the sustainability of the components of the campus and suggesting appropriate mechanisms for them. The study concluded that there are many problems in sectors, landmarks, paths, car parks, functional nodes, and edges, and the lack of application of the principles and standards of sustainable design in them. Therefore, a number of mechanisms have been suggested that can be implemented to overcome these problems and achieve the sustainability of the Anbar university campus.

Barbara E.A. Piga

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Case Studies in New Classical & Traditional Design: Living on Campus: Student Housing Models

with Melissa DelVecchio

August 12, 2020

This seminar series explores the design and execution of new work from the practitioner’s perspective. Contemporary classical and traditional design encompasses architectural work for all building types, at all scales and budgets, and in the allied fields of urban planning, landscape, interiors and the artisan and building trades. The series aims to explore solutions to contemporary design challenges, foster critical discussion of recent work, and demystify the complexities of how unique projects come together.

In this session of the project forum series, Melissa DelVecchio, partner at Robert A.M. Stern Architects, leads an in-depth discussion on the topic of student housing models. Living on campus is central to the U.S. college experience, but student housing poses a big challenge as schools work to make their campuses safe for students to return this fall. Melissa will present recent student housing models such as shared suites designed for the new residential colleges at Yale University; single bedrooms with shared social spaces designed for a living-learning college at Tsinghua University; and micro apartment studies prepared for an unbuilt university housing project in Florida. The presentation will be followed by a conversation about the student housing models we might see in the future, particularly in response to COVID-19.

About the Instructor

Melissa DelVecchio is a partner at Robert A.M. Stern Architects. She is the design lead for many of the firm’s most complex academic and institutional projects, and directs the Research Department. Building upon her education that included an intensive study of classical architecture and a subsequent immersion into contemporary design, her work synthesizes tradition and invention, reinforcing the many visual, social, environmental, and cultural influences that give places identity and meaning. Melissa’s projects include two new residential colleges at Yale University and the first LEED Gold-certified academic building in China. She is currently working on the restoration and adaptive reuse of the Schwarzman Center at Yale, a historic Carrère & Hastings’ building that will be transformed into a social hub for the university’s students; and the Raclin Murphy Museum of Art, the anchor for the University of Notre Dame’s new arts district.

Melissa is a fellow of the American Institute of Architects and a member of the Richard H. Driehaus Prize jury, the Rafael Manzano Martos Prize jury, and the RAMSA Travel Fellowship jury. In Spring 2021, she will serve as the Robert A.M. Stern Visiting Professor of Classical Architecture at the Yale School of Architecture.

What You Will Learn

• To demonstrate how contemporary student housing design can benefit from a deeper understanding of historical precedent.
• To highlight various student housing design models from the early-twentieth century to the present, with a careful study of private versus shared social spaces.
• To examine key issues regarding student housing and the current pandemic.
• To discuss potential student housing models after COVID-19.

2020 Summer Studio Retrospective

This course is presented as part of the 2020 Summer Studio Retrospective , a four-week series of daily online content inspired by the ICAA's Summer Studio in Classical Architecture program and the many students who have been impacted through its unique course of study. You can find additional programs in this series here .

Tags: education , video , Summer Studio Retrospective , video course , recorded event

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10 things to remember while designing a university campus

The cut-throat competition in today’s work industry pushes students to pursue an alma mater that makes them future-ready. The crucible of this process is the incubation space that the students spend most of their time at, aka the University campus. This makes us designers responsible for creating a collaborative environment that can mold and adapt itself to the changes of the century, thus guaranteeing a master plan for the entire community. There are several challenges to the design of such a large-scale project.

Here are ten things to keep in mind for an efficient and intelligent University campus design.

1. ADOPT URBAN PLANNING STRATEGIES

Designing a University campus is like planning a mini town. It is imperative to imagine the project’s scale for an urban public realm and design on an axis. As one of society’s most treasured assets, its planning also needs to be aligned with the pace of facility investments and uncertain funding streams so that the design is flexible and in tandem with future developments.

In a low, dense suburb, there are forty-four buildings that follow an open space design at the University of New South Wales (Sydney, Australia).  The pedestrian-friendly campus is axially planned, directing the movement and giving a sense of order and circulation. It also accommodates transitional and social activities in its open lawns.

2. DRAW ATTENTION AND PAINT AN IDENTITY

It is easy for newcomers to get lost in the maze of buildings and pathways at a University campus. A focus helps visually dominate a space acting as a landmark to help people navigate. This focus also has cultural and social significance and can be a center for recreational activities. It is an integral part of the design that draws eyes towards it.

At Simpson College in Indianola, Iowa, the pedestrian plaza manifests the institute’s maple leaf history. The central sculptural element has panels of cut-weathering steel with ‘whispering maple’ figures with a low seating area. Subtle color-changing LED change the sculpture’s hues at night. These are guiding landmarks at the crossroads of the central plaza and create its unique identity.

3. PRACTICE PLACEMAKING & UTILIZE VARIETY OF SCALE

From large-scaled quadrangles to small-scaled connective spaces such as corridors, the campus has to serve multiple functions on a variety of scales. Architects need to decipher the correlation between activities so that the design promotes their inter-relatedness. It allows the seamless integration of core facilities such as places of social and cultural milieu with the academic blocks (research labs, lecture halls, studios, etc.).

As seen in the master plans for The University of Washington’s campus, the design facilitates an insightful experience that integrates all the stakeholders- administration, academia, and the industry. With divisional blocks and multiple places of social interaction, the campus brings about serendipitous learning.

4. CREATE THE DIGITAL REPOSITORY

Progressive digitalization has reduced our visits to the traditional silent sanctuaries of paper scrolls. But the quality environment a library offers is still popular among the students of the higher education arena. Thus, there is a need not for a repository of paperbacks but of contemporary multi-functional spaces that encourage learning by harnessing the technological innovations of the age.

The Joe and Rika Mansueto Library at the University of Chicago’s campus is the epitome of a state-of-the-art reading nook. By shifting the book storage underground and incorporating an automated retrieval system, the designers have tapped into the potential of natural lighting through the clear glass dome. This has increased productivity and allowed sustainability to thrive.

5. USHER CREATIVITY WITH INCUBATION SPACES

With the start-up culture on the rise, dedicated pockets that spark discussions are required where students can experiment, fail, and start over. These spaces help forge connections of academia with the industry. In the advanced technological setting, it is an architect’s responsibility to create an environment that promotes a flexible learning environment and encourages the entrepreneurial spirit.

At the University of East London, Knowledge Dock caters to each user’s needs with a fluid work environment. The co-existence of active and focus spaces in layers, as seen in its plan along with adaptable collaboration areas, mobile writable screens, and bold graphics, makes this a bustling center of electricity and innovation.

6. THE CAMPUS LIFE EXPERIENCE

On-campus residency is an integral part of the whole college experience for the students. The design should cater to the array of housing needs of the students as well as the teachers. These living spaces should accommodate the contemporary student’s hectic lifestyles and provide all the necessary amenities.

The residential facility at Phoenix for students at Arizona State University is an example of world-class planning. Special care is taken to mold spaces such as dining halls with movable furniture and walls for video projection so that students can learn and create in the comforts of their residence halls, irrespective of the time of the day. The residence allows students to be seen yet offers them privacy.

7. BIOPHILIC NEED OF THE HOUR

Scientific studies have proven the therapeutic effect of biodiversity on stressed minds. Thus, tending to the campus landscape is essential because it offers a sense of retreat to the students dabbling with multiple deadlines. A lush green lawn is always a welcome sight for the people of any age group. Dotted with plants, these spaces generate a healthy mindset for the entire community.

The Espace Bienvenüe at Cité Descartes’ campus in Paris is an innovative project which focuses on ecology. Contrasting the flat site, the 200-meter-long, undulating landscaped gardens built over a concrete structure offer exuberant panoramic views. They bring fresh air to the dense complex, thus reinforcing a spirit of relaxation and peace.

8. DESIGN FOR ALL

The campus needs to have a barrier-free approach. The designer should ensure all areas, whether recreational or institutional, and all pedestrian routes should follow inclusive design guidelines. All paved walkways must have contrasting edge demarcations, provision of handrails, and curb cuts. There should be separate toilet stalls in public spaces for the disabled.

The University of Texas at Arlington has been a trailblazer in building an accessible campus. They have replaced every single door handle from a knob to a lever across the uni. By setting up an Adaptive Resource Center, UTA has sent across the message to the entire world that inclusive architecture isn’t about installing ramps in your design.

9. FOCUS ON SPORTS AND HEALTH

All work and no play make Jack a dull boy. Planning of sports grounds, gymnasium, and even rejuvenating spas are of immense importance for the University. These need to follow Olympic standards and guidelines. Medical health centers also need to be planned meticulously. This building block needs to be accessible to all at all times.

The gymnasium’s dynamic design at Shanghai University of Science and Technology lies at the starting point for the residential quarters for teachers and students. It is a dominant landmark whose scale and landscape harmonizes with the surroundings of towering dormitory buildings and encourages sporting fervor among the residents.

10. USE SUSTAINABILITY AS AN EDUCATIONAL TOOL

Campus design embodies visions and mirrors the goals of the University. Sustainability is one such core value that needs to reflect in the design as the carbon footprint of a large-scale project such as this can have a profound impact on the environment.

UC Merced’s buildings stand to realize its values of conservation and resource-efficiency. As a green building pioneer, all of its buildings have already met or are working to meet LEED standards. This future-oriented campus has aligned itself to the broader academic goals proving to be one of California’s best institutes.

Radhika Jhamaria, an Architecture undergrad at NIT Jaipur, loves to travel and explore the world as a design enthusiast. She believes that one should always follow their heart and she pours hers into literary escapades. You may occasionally find her strumming her beloved guitar.

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Design Process of a Campus Plan: A Case Study of Duzce University Konuralp Campus

• International Journal of Engineering Research and Applications 7(4):2248-962250
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8 Great Campus Landscapes

College and university campuses are increasingly embracing sustainability in their development and redevelopment projects. These campus landscapes manage runoff, reduce potable water use, and serve as learning laboratories for students interested in green technologies. Just as importantly, the landscapes serve as a visual representation of the campus community’s commitment to sustainability and define campus or department identity by serving as the backdrop for study, relaxation, recreation, and events.

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Avasara Academy / Case Design

• Curated by María Francisca González
• Architects: Case Design
• Area Area of this architecture project Area:  14200 m²
• Year Completion year of this architecture project Year:  2019
• Photographs Photographs: Ariel Huber
• Furniture : Vishvakarma Furniture
• Project Management : AMs Project Consultants
• Structural Engineering : Strudcom , Nikhil Inamdar
• Climate Engineering : Transsolar | KlimaEngineering , Pratik Raval
• Interior Work and Finishes : Mortar Construction , Rameshwar Bhadhwa
• Civil Construction : Vaichal Construction
• Partner And Principal Designer:  Samuel R. Barclay
• Project Architects:  Ami Matthan, Dhwani Mehta, Shoeb Khan, Simone Picano, Ji Min An, Tofan Rafati, Anne Geenen, Aamod Narkar, Farhaan Bengali
• Landscape Implementation:  Farhaan Bengali
• Furniture Design:  Paul Michelon
• Intern:  Chirag Bhagat
• Colour:  Malene Bach
• Landscape Architect:  Hemali Samant
• Founder Of School:  Roopa Purushothaman
• Head Of School:  Joseph Cubas
• City:  Maharashtra
• Country:  India

Text description provided by the architects. Settled into the valley slope above the small village of Lavale, Avasara Academy is a residential school for economically disadvantaged young women in western India.

Located just outside the urban periphery of Pune, the school lies at the edge of a rural landscape and a rapidly developing township known as Knowledge City.

Uniquely positioned to take advantage of locally shared education resources and incredible social, religious, and economic diversity, Avasara is rapidly establishing itself as a leader in the education and development of young women in India. 

Comprised of a collection of simple concrete structures shrouded in bamboo and arranged around an informal series of walkways, courtyards, gardens and terraces, the built environment of the campus was designed for economic efficiency as well as flexibility and readiness to adapt both during and after the design process.

The rudimentary framework of each building enabled a process of dialogue and collaboration amongst a diverse group of builders, designers, farmers, artists, craftsmen, and engineers who share the belief that collaboration and empathy lie at the core of all good work.

Together with these contributors we have created moments of hospitality, social interaction, B6 reflection, play, ritual, seclusion, performance, and comfort. Intended for a variety of uses, these public and private spaces aspire to give a sense of familiarity and intimacy to the young women living and studying on campus.

Culled from local and universal examples of academic, domestic, public and sacred spaces and evolving through a process of inclusion and thoughtful attention to both physical and social environments, the project developed in response to what was already there; climate, landscape, materials, routines, traditions and memory, to create a sanctuary for learning.

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• Published: 12 August 2024

Case Study on the design optimization of the positive pressure operating room

• Ghaim Man Oo 1 ,
• Komsilp Kotmool 1 &
• Mongkol Mongkolwongrojn 1  

Scientific Reports volume  14 , Article number:  18671 ( 2024 ) Cite this article

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• Energy science and technology
• Engineering

Ventilation systems of operating rooms (ORs) are significantly important in preventing postoperative wound infections that can cause morbidity and mortality after surgery in or out of the hospital. This study aims to identify the optimum overpressure for efficient operation while reducing the risk of surgical site infections (SSIs) based on the actual OR with the help of computational fluid dynamics. The species transport model, Lagrangian discrete phase model, and turbulent standard k- \(\upvarepsilon \) model are mainly used for the transient numerical study to improve the performance of the OR and reduce SSI cases. Four OR schemes were initially calculated for the best location of the patient on the surgical table. The results revealed that the modified position 90˚ is the best location with the minimum CO 2 and BCP concentrations. The investigated operating room could host up to ten surgical members with the optimum overpressure of 5.89 Pa and 0.56 m/s of supply velocity under the standard cleanliness level. Modifying the supply surface area will enhance the performance of the operating room by providing a cleaner zone and maintaining the desired room pressure, even with a low airflow rate. This optimization scheme could guide practical applications in all positively pressurized operating rooms to address issues related to overpressure effects.

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Introduction.

Nowadays, cleanroom technology is widely used in many applications such as pharmaceuticals, microelectronics, flat panel displays, aerospace, hospitals, and miscellaneous applications 1 . Among them, it is estimated in hospitals that there are annually more than 290, 000 incidences of surgical site infections according to the U. S Department of Health and Human Services (HHS) 2 . In order to reduce the risk of contamination and SSIs that can cause nearly 99, 000 deaths per year, an operating room must maintain a controlled particle level as a positive pressurized cleanroom. Positive pressurization means designing a specialized controlled environment where the air pressure inside the room is maintained at a higher pressure than the adjacent spaces. This higher pressure ensures that airflow can prevent the entry of contaminants from the external environment and act as a barrier against the ingress of airborne particles and microbes.

During surgery, releasing contaminated particles by internal and external environments of ORs may cause SSIs. The external contaminants come from nearby road traffic, industrial activities, or natural elements like pollen or dust storms and these contamination effects can be prevented by using positive pressure cleanrooms. On the other hand, the remaining internal contaminated sources in the operating rooms are mainly from the surgical staff, surgical instruments, and the surgical site itself 3 . Therefore, cleanrooms must be designed and used according to their cleanliness level, which is determined by the maximum allowable concentration of particles of a specific size within the controlled area. This classification is based on globally accepted standards, such as Federal Standard 209E or ISO 14644-1. Likewise, all the operating rooms were classified into 10, 000 class or ISO 7 with the maximum particle count limits for different particle sizes, such as 0.5 µm, 1 µm, and 5 µm 4 . To achieve the required level of cleanliness, ventilation systems are the main tools for the essential parameters of particulates, air change rate (ACH), temperature, pressure, airflow patterns, vibration, noise, and so on.

Despite years of study and substantial research regarding operating room ventilation systems, there is still little or no general agreement about the effect of overpressure concerning particle dispersions inside the ORs. Therefore, the most relevant research studies are reviewed to highlight the new research requirements. Yan Lin Wu and Azka Hasya Hanifan analyzed five different ventilation designs such as the vertical laminar flow type (VLF) and horizontal laminar flow type (HLF) concerning slot fan 5 . They considered CO 2 as a pollution source inside the operating room and the desired pressure was 15 Pa for their experimental and numerical work. From this study, they found that using a laminar airflow type was most powerful in removing contaminant CO 2 around the surgical site but using a slot fan can reduce the turbulence effect in the hospital operating room. Similarly, S B Thool et al., and Zhijian Liu et al., also observed different ventilation systems such as vertical laminar airflow ventilation (VLAF), horizontal laminar airflow ventilation (HLAF), and temperature-controlled airflow ventilation (TAF) 6 , 7 . They calculated the particle emission effects from five surgical staff and assumed these BCPs were released from their legs and feet. They recommended that the VLAF air supply system can give a faster diffusion rate of BCPs although TAF systems are strong vertical downward air supply to protect the operating area. Similarly, A.C.D. Slicandro et al. analyzed the effectiveness of three different ventilation systems by investigating three different OR layouts 8 .

Mitchell C. Weiser et al. measured the mean pressure of six different operating rooms due to the opening effect of the main door and inner door of ORs 9 . They suggested that OR door usage during the performance of the operation should be limited to prevent the influx of contaminated external air due to the increased foot traffic. The authors noted that the mean pressure is the minimum positive pressure of 0.01 inH 2 O (2.5 Pa) specified in the ASHRAE standard but all the ORs operated approximately 9 Pa higher than this mean value. Moreover, Fu-Jen Wang et al. presented a comprehensive field measurement test and numerical calculation based on the actual operating room to meet the thermal performance and minimum contamination control requirement 10 . In their study, they found the overpressure effect compared with the desired design standard and reported only the relation between supply face velocity and room pressure with three different velocities. As a result, there is still no limitation of maximum overpressure effect on the operating room. In another study, Zhijian Liu et al. also investigated the optimum range of supply velocity, 0.24—0.29 m/s based on the bioaerosols deposition in the surgical area by applying four different velocities 11 .

As mentioned in the literature above, much of the related research has identified the most suitable type of ventilation system, such as (VLAF), in mitigating potential risk factors associated with SSI. However, the impact of the maximum overpressure concerning aerosol dispersion from the surgical staff present in the ORs has not been considered until now. Therefore, to highlight this significant crucial gap, the previous works are compared as indicated in Table 1 and different desired positive pressure standards for operating rooms are studied according to various countries in Table 2 . Most countries still lack a precise positive pressure value, but some have assigned a minimum pressure value. Although the minimum positive pressure, 2.5 Pa, is shown based on design standards, the relevant maximum overpressure could not be exactly mentioned, and it has not yet been included as a mandatory guideline. This overpressure effect can cause energy consumption and a high airflow rate when the fan is operated beyond the fan operating point, which could lead to unstable operation, reduced fan efficiency and life span, and increased noise and vibration.

Therefore, the main objective of this paper is to determine the optimal overpressure by investigating the positioning of the operating table and the number of surgical staff in the operating room. This analysis considers various indoor air quality parameters, such as contaminant and BCP concentrations due to breathing and speaking, CO 2 concentration, room pressure, supply velocity, temperature, ACH, and power consumption. To meet this main objective, the optimal position of the patient on the surgical table is numerically investigated by comparing four schemes. Additionally, eight different configurations are analyzed to study particle dispersion effects with the surgical staff in masked and unmasked conditions. The numerical model used was first verified against previously published work and then validated with measurement tests carried out in an actual operating room in Thailand.

System description

The actual investigated operating room within a hospital in THAILAND was chosen as the geometrical model for this study. The photograph and HVAC system layout of this OR are shown in Fig.  1 . The supply air (SA) through the fan from the air handling unit (AHU) was supplied to the OR by four diffusers symmetrically placed in the center of the ceiling. High-efficiency particulate air (HEPA), H14 HEPA is used to filter the air particles with an efficiency of 99.999% on 0.3 µm. The clean air entering the OR is extracted from the three outlets as the exhaust air (EA). All exhaust outlets were located 0.32 m above the ground with length and width of 0.6 m and 0.57 m respectively. The operating room was designed according to the classification of ISO 7, class 10, 000 with the acceptable maximum particles per cubic meter at three different sizes 0.5 µm, 1 µm and 5 µm are 352,000, 83,200 and 29,300. The design specifications of the investigated OR included different parameters such as temperature of 18 ± 2 ℃, relative humidity of 50 ± 10%, and pressurization at 7.5 ± 2.5 Pa. The dimensions of the actual OR were a length of 8 m, width of 7 m, height of 3 m, total room surface area of 44.81 m 2 , and total air supply inlet area of 2.36 m 2 respectively.

The operating room where the OR measurements were taken; ( a ) photograph; and ( b ) layout of the HVAC system.

The operating table was placed in the middle of the room and below the center of the supply inlets as indicated in Fig.  1 . (a). The length, width, and height of this surgical table were 2.5 m, 1.2 m, and 0.2 m respectively; the middle support was 0.35 m, 0.35 m, and 1 m respectively; the remaining step was 0.65 m, 0.65 m, and 0.3 m respectively. There were two to ten surgical staff and a patient lying on the bed. Their body temperature is taken as the normal body temperature of 37 ℃ 19 and the heat flux of humans is 32 W/m 2 based on the human latent heat at 205 BTU/hr which is approximately 60W 20 . The height of all the surgical staff was assumed about 6 feet and the body surface area used as the adult men unit of 1.9 m 2 , 21 . For BCP analysis, two types of internal contaminant sources are released from the human mouth. The first contaminant is CO 2 gas with a velocity speed of 0.18 m/s and a concentration rate of 38, 000 ppm 22 . In the second one, human breathing and talking particles are mainly considered at speeds of 1 m/s and 5 m/s with particles of 134 particles/s and 195 particles/s 23 , 24 .

In the present study, there are three main approaches to improve the performance of the investigated operating room with the help of computational fluid dynamics (CFD) by using ANSYS Fluent. Firstly, the only operating model is numerically calculated and validated the accuracy and agreement of the results compared with the measurement results. Secondly, the validated model is modified by investigating four schemes of patient’s different positions on the surgical table to choose the best position concerning the contaminant deposition of CO 2 and discrete phase model (DPM) concentrations. As a final analysis, eight configurations by adding different numbers of surgical or healthcare staff are studied based on the required cleanliness parameters of pressure, number of particles, ACH, power consumption, supply air velocity and area, and temperature. In addition, the investigated operating room is modified by changing the supply surface area to improve the performance of the OR.

Methodology

Measurement test.

The most important thing of ORs is to prevent airborne contaminants from settling in the desired surgical field. For the numerical calculation, the field measurement tests were carried out to determine the basic required parameters of temperature, pressure, supply velocity, exhaust velocity, and number of particles and then measured all the necessary dimensions of the operating room. This measurement test for the airflow was started to measure during the operating room at rest after running for 30 min. On the other hand, an airborne particle count test was also performed when the investigated operating room was purged for at least 12 h before testing commenced. For these airflow and particle measurement tests, the accuracy of measuring instruments is stated in Table S1 of supplementary material. The airflow rate and air change rate are calculated based on the measured supply velocity, supply surface area, and total room volume. Furthermore, some of the measurement data are used as the boundary conditions of the numerical investigation, and the two verification parameters of room pressure and exhaust velocity are calculated from the simulation.

The CFD technique has become a powerful alternative for predicting the airflow field in enclosed environments due to the rapid advances in computer capacity. In this study, CFD software (Fluent 2020) was used to simulate the airflow, BCPs motion, and contaminants concentration inside the operating room. The three-dimensional transient incompressible airflow simulation is carried out with the help of the Fluent program which uses the finite volume approach to solve the governing equations like continuity, momentum, and energy Eqs.ref 25 , 26 , 27 . This fluid flow inside the indoor operating environment is taken into fully turbulent and the standard k − ε model is used due to its accuracy concerning the experiment-validated results and its low computational cost 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 . These transport equations of the turbulent k − ε model can be obtained as follows 25 , 27 :

where k is the turbulent kinetic energy; ε is the dissipation rate; \({\sigma }_{k}\) and \({\sigma }_{\varepsilon }\) are the turbulent Prandtl numbers for k and \(\varepsilon \) ; \({\text{C}}_{1\upvarepsilon }\) , \({\text{C}}_{2\upvarepsilon }\) and \({\text{C}}_{3\varepsilon }\) are constants; \({\text{S}}_{k}\) and \({\text{S}}_{\upvarepsilon }\) are user-defined source terms; G k is the production of kinetic energy by the mean velocity gradients; G b is the production of kinetic energy by buoyancy; and the contribution of the variable dilatation incompressible turbulence to the total dissipation rate is denoted by Y M .

For the investigation of contaminant concentrations, the species transport model is used to calculate the volumetric reactions in the operating room without any chemical reaction. CO 2 is applied as a pollutant gas, and the local mass fraction of each species, Y i can be predicted through the solution of a convection–diffusion equation for the ith species as follows:

where J i is the diffusion flux of species i; S i is the rate of creation when any user-defined sources are added; and R i is the net rate of species i formation through the chemical reaction. All the CO 2 concentration levels are calculated up to 900 s to save computation time and cost because the trends of CO 2 decay are nearly constant between 400 and 900 s as stable conditions inside the operating room. To calculate the concentration of the pollutant CO 2 , the essential parameter of parts per million (ppm) needs to be considered as the volume or mass ratio between the pollutant component and the solution in the following Eq. ref 41 , 42 .

where ppm is parts per million; the mass of solute represents the mass of injected particles, and the mass of solution represents the total mass of injected particles and air inside the room.

The Lagrangian discrete phase model is applied to predict the trajectory and concentrations of the particles released from the patient and surgical staff by breathing and talking inside the operating room. In ANSYS Fluent, droplet particles are assumed to remain spherical throughout the computational domain, and the mass flow rate of particles is calculated based on Eq. ( 5 ) ref 43 . These particles in the moving fluid can be investigated by integrating the force balance on these particles as written in Eq. ( 6 ) ref 25 , 44 , 45 .

where \({\text{m}}^{\bullet }\) is the mass flow rate of particles; n and ρ d are the number and density of particles; r is the radius of particles and t is the time taken at second.

where \({\uprho }_{\text{p}}\) , \({\uprho }_{\text{f}}\) and u p and u are the density and velocity of particle and fluid; g is the gravitational acceleration; F D is drag force; and F others represents the additional forces including Brownian force, Saffman lift force, virtual mass force, pressure gradient force, and thermophoretic force. Among them, gravity and drag forces are mainly considered for the particles floating into the indoor air environment 45 , 46 . Brownian and Saffman lift force also need to be considered due to the acting force variation on the sub-particle size of less than 1 µm ref 25 , 47 , 48 . Moreover, the drag model must be considered due to the smaller particles compared with the element size of the computational domain.

Physical Geometry and Boundary Conditions

The physical model is established as a 3D computational air domain according to the size of the operating room hospital in Thailand. The first model has four supply inlets, three exhaust outlets, a surgical table and lamp, and general lights inside the operating room. After validating the numerical results and the measurement test results with the first geometry, this computational domain is modified by adding patients concerning four different positions as indicated in Fig.  2 with detailed dimensions. The investigated operating room has only three exhaust outlets which can delay and recirculation of aerosol particles effect from the patient’s mouth. Therefore, it is important to consider the best patient’s position on the surgical site together with minimum CO 2 and BCP concentration. The different numbers of surgical staff are considered from 2 to 10 staff around the patient’s surgical table after choosing the best patient location inside the operating room. For these different configurations, patient and surgical staff models are arranged and described in Fig.  3 .

The physical geometry of the investigated operating room with four different schemes of patient positions on the surgical table: original position at 0˚, modified position at 90˚,180˚ and 270˚.

Configurations of the patient and different numbers of surgical staff:( i ) Only patient ( ii ) Two staffs, ( iii ) Four staffs, ( iv ) Six staffs, ( v ) Eight staffs_M1, ( vi ) Eight staffs_M2, ( vii ) Ten staffs_M1 and ( viii ) Ten staffs_M2.

The essential boundary data are measured and applied as boundary conditions based on the actual operating room. The supply airflow from the AHU is defined as the boundary of velocity inlet and these velocities are applied uniformly and acting normal to the boundary in the four supply faces. The average velocity in the working area of the surgical site should be 0.2–0.25 m/s according to the “Architectural Technical Code for Hospital Clean Operating Department” 49 and 0.2–1 m/s is also a comfort zone for Thailand people 50 . The three exhaust outlets are considered as pressure outlet boundary type and the positive pressure difference is calculated between the operating room and outside air equal to atmospheric pressure. The outside walls of the operating room and all the human models are applied as wall boundary type, which is assumed heat flux of 32 W/m 2 for the human body surfaces. The thermal comfort condition for Thailand people is 22–27 ℃ and the temperature in the operating room should be 21–25˚ 50 . Furthermore, the respiratory system of breathing and speaking from the human mouth is set velocity inlet type. The density of the particle released by a human is assumed 1000 kg/m 3 as the same density of water 23 , 51 . All the specific boundary values are listed in the following (Table 3 ).

Meshing and grid independent verification

The mesh structure discretized by a tetrahedral shapes technique is proposed for the whole computational domain of the operating room due to the advantages of setup time and computational expense of the complex geometry. A Semi-Implicit Method for Pressure-Linked Equations (SIMPLE) algorithm and the least square method were used for the gradient discretization 52 . The refinement mesh is generated in the main areas of supply inlets and exhaust outlets to focus on the near-wall effect as shown in Figure S1 of supplementary material. The highest Y + value, 56.6, occurred near the exhaust outlet while most Y + values near the walls are nearly 1. Therefore, the standard wall function is adopted to link the solution variables and corresponding quantities at the near wall cells in the k- \(\upvarepsilon \) turbulent model. The accuracy of the solution is mainly due to the dependency of the number of elements on the numerical results. In this study, seven different types of element sizes are calculated for the output parameters of room pressure, exhaust velocity, and computational time as shown in (Fig.  4 ). Among the different element sizes, the solutions are stable from 3,135,615 to 27,883,469 with a computation time of 12.5 and 72 h. Therefore, the 3,135,615 element size is the most suitable one for future simulations to save computing time. The convergence criterion is also set the value of 10 −4 for all the residuals 10 −6 except for the energy variable and the relative error between the consecutive element size for the output variables like room pressure, and exhaust velocity is a maximum value of 1.65% under the acceptable error percent, which must not exceed 5% 53 .

Mesh independent graph.

Model Validation and field test validation

Airflow validation.

The authors performed full-scale field airflow measurements to validate the numerical simulation implemented in this study. Additionally, the current numerical airflow model is validated against published experimental and numerical work by Yang et al. (2009) 54 . Figure  5 . (a) displays the computational domain of a clean ward with an adjacent bathroom. Velocity inlet and pressure outlet boundary conditions are mainly applied for the numerical simulation. The supply air velocity for the clean ward is 0.28 m/s and 0.33 m/s in the bathroom. k ε turbulent model is chosen for the airflow, and the velocity measuring points are taken from three different planes of A, B, and C as shown in Fig.  5 . (b). The air velocity measurement points were set up at three heights: 0.8 m, 1.2 m, and 1.6 m, respectively, and are compared in (Fig.  6 ) The findings indicated that the simulated air velocity values agree with the previous numerical and experimental values at each measurement point. Hence, replicating the airflow model of a clean ward for the current numerical model of the operating room is feasible. After proving the correctness of the computational model, the current field measurement test and numerical simulation of the operating room are calculated and compared. When the measurement tests were recorded in the actual operating room, the supply air velocity varied from 0.75 to 0.82 m/s, and the room pressure was also from 11.1 Pa to 12.6 Pa. Therefore, the minimum condition, a supply velocity value of 0.75 m/s is selected as the first basic input parameter for simulation, and the two output parameters of room pressure and exhaust velocity are compared clearly in Table S2 . In general, the relative error percent for airflow and turbulence in enclosed environments can be defined as a good agreement under 10% 55 . In this work, the error percent for room pressure is 1.51% and exhaust velocity is 2.29%. Therefore, the simulated flow field agrees well with the measurement values.

( a ) The layout of the clean ward with adjacent bathroom, ( b ) Floor plan of the air velocity measurement points.

Comparison of measured and simulated air velocity at three planes in the clean ward: ( a ) Plane A at 0.8 m height, ( b ) Plane A at 1.2 m height, ( c ) Plane A at 1.6 m height, ( d ) Plane B at 0.8 m height, ( e ) Plane B at 1.2 m height, ( f ) Plane B at 1.6 m height, ( g ) Plane C at 0.8 m height, ( h ) Plane C at 1.2 m height and ( i ) Plane C at 1.6 m height.

Particle validation

For the particle trajectory validation, the same Lagrangian method was adopted from the previous study that investigated the aerosol dispersion in the negative pressure room 35 . The experimental results by H. Jin et al. (2009) were used to validate the current numerical model for particle tracking 56 . According to the experiment setup, gas, and particle mixing flow are injected into the ventilated scale chamber with a velocity of 0.5 m/s and particle diameter of 0.3 µm. This test chamber is equipped with one inlet and three outlets labeled O 1 , O 2 , and O 3 , each with rectangular shapes measuring (0.2 \(\times \) 0.3) m 2 , as depicted in Fig.  7 . (a). These outlets can be opened and closed freely to create different kinds of flow fields. The density of particles is 2.1 \(\times \) 10 3 \(\text{kg} {\text{m}}^{-3}\) and the measuring point is considered in the center of the chamber for the current validation. The numerical particle concentration is compared with experimental data by calculating the average value of particle concentration inside the chamber as shown in Fig.  7 . (b) and (c). Even though the experiment data showed some fluctuations, the simulated concentration findings closely matched the experiment's growing trend. Thus, the current simulation strategy is adequate for investigating the particle dispersion and concentration of the operating room model.

( a ) The layout of a ventilated scale chamber. Time-dependent particle concentration with a gas velocity of 0.5 m/s: ( b ) with outlet O 1 open and ( c ) with outlet O 2 open.

Furthermore, the particle count test was conducted after completing all other tests. The test considered ten separate operating room (OR) areas, as shown in Figure S2 . Counters were set to sample at a rate of 1 ft 3 /min, and at least one sample was taken at the center of each grid, at a height of 1 m above the floor. The average number of particles per cubic meter was validated through numerical calculation, showing good agreement with an error percentage of 6.8%, as listed in Table S3 . This numerical result for particle concentration was based on a speaking model involving seven surgical staff as the main particle sources in the OR, reflecting the presence of seven individuals during the measurement time.

Gaseous validation

The present numerical model for simulating CO 2 concentration levels in the investigated OR was validated by comparison with the previous experimental work of K. C. Chung et al. 57 . In the experimental test chamber, one inlet and outlet diffuser of (0.4 m \(\times \) 0.4 m) size is located at the opposite walls as shown in Fig.  8 . (a). During the test, the supply velocity is 1.36 m/s together with the outdoor CO 2 contaminant effect of 350 ppm and the initial background value starts from 2000 ppm. The validation points are calculated as the averaged values based on the two planes of the X–Y plane and X–Z plane respectively. Figures  8 . (b) and (c) show good agreement between the present predictions and the results of K. C. Chung et al. 2001.

( a ) Schematic layout of the experiment test chamber; Comparison of CO 2 -decay levels for ( b ) X–Y plane, ( c ) X–Z plane.

Results and discussions

Choosing the position of the patient on the surgical site.

After validating the numerical simulation results, modifications were made to the investigated operating room by considering four distinct positions for the patient on the surgical bed. The four distinct positions mentioned are chosen as the basic models to determine the optimal operating bed position. This is essential because the operating table needs to be centrally located within the room's four walls. This central placement ensures there is sufficient space around the table for other necessary operating equipment and tables. These positions include (1) the original orientation with the patient lying on the surgical table at 0 degrees (Org_0°), (2) the patient lying on the surgical bed at 90 degrees (Mod_90°), (3) at 180 degrees (Mod_180°), and (4) at 270 degrees (Mod_270°), as depicted in Fig.  2 . The CO 2 concentration in indoor air and its associated health implications are typically defined within the range of 400–1000 ppm, which aligns with ASHRAE standards and previous research 58 , indicating good air exchange in occupied spaces. Exceeding 1000 ppm can lead to adverse effects such as headaches, dizziness, nausea, and other symptoms. To determine the optimal patient location on the surgical table, CO 2 concentrations are initially compared for the patient-only model under varying supply inlet velocities of 0.53 m/s, 0.75 m/s, and 0.82 m/s, as illustrated in Figure S3 . These velocity variations can cause the direct increasing effect of ACH (33, 47, and 52 ACH) and room pressure (5.58, 11.27, and 12.36 Pa) as the same relation in Fig.  9 . The decay in CO 2 concentration correlates directly with the supply velocity and room pressure; higher velocities and pressures result in more pronounced reductions in CO 2 concentrations across different patient positions within the operating room. All CO 2 concentrations are assessed as average values across the entire operating room domain.

Comparison of CO 2 concentration in four different schemes with three different velocities: ( a ) only patient model, and ( b ) two staffs model including patient.

Furthermore, the effect of CO 2 concentration decrease is analyzed based on two computational models: one with only the patient and the other with two staff members including the patient. This analysis encompasses four different schemes across various supply velocities, as illustrated in Fig.  9 . During durations of over 400 s and 600 s, the CO 2 concentration levels reached stable levels in both the patient-only model and the two-staff models. The differing durations for stabilization can be attributed to the higher release of contaminants resulting from multiple individuals present in the operating room. Therefore, the impact of surgical staff on contaminant concentration emerges as a critical parameter in addressing surgical site issues. Although all the CO 2 concentration trends decrease under the acceptable CO 2 level, one of the significant trends in the modified 90˚position (Mod_90˚) can give the lowest concentration level compared with other positions.

Respiratory particles are small enough to facilitate the airborne transmission of microorganisms within them, thus as aerosol particles 59 . To calculate DPM concentration, the primary methods involve quantifying particles emitted through human actions such as speaking and breathing, which generate varying numbers of particles per second. Figure  10 analyzes the particle deposition effect from only one patient by calculating the breathing system in four schemes according to various velocities concerning pressure. Based on the numerical simulation results, it can be observed that low supply velocity cannot reduce DPM concentration in all schemes except from the modified position at 90˚ as described in Fig.  10 . Furthermore, DPM concentration in the Mod_180° and Mod_270° positions exhibited increasing deposition over time, despite high supply velocities of 0.75 m/s and 0.82 m/s. This is attributed to the contaminant source originating from the patient's mouth being situated away from the exhaust outlets in these models. To indicate the clear DPM concentration effect, four different schemes are compared with various velocities, as shown in Figure S4 . The DPM concentration trends inside the operating room are nonlinear due to variations in the position of the contaminant source across different schemes. This variability can result in particle escaping effects from the different exhaust outlets. Additionally, it was noted that particle concentrations did not exhibit the same trend as CO 2 due to their distinct dynamics and rates of deposition. Among these four schemes, the Org_0˚ and Mod_90˚ schemes can extract the lowest DPM concentration decay trends and these trends are nearly identical at the supply velocities of 0.75 m/s and 0.82 m/s. On the other hand, DPM concentrations at Mod_90˚ can be reduced more than in the Org_0˚ scheme at 0.53 m/s. Therefore, according to DPM concentration results, the modified position at 90˚ scheme (Mod_90˚) shows better performance than the other schemes.

DPM concentration from only patient in the operating room with different velocities, 0.53 m/s, 0.75 m/s, and 0.82 m/s.

To highlight the optimal patient position on the surgical table, the number of particles emitted during the breathing process, with a particle size of 0.5 µm, is compared across the entire room volume, as illustrated in Fig.  11 . The particle deposition numbers at only the patient model are nearly the same for Org_0˚ and Mod_90˚, especially high supply inlet velocities. However, the particle deposition effect is quite different when the number of people increases inside the operating room. The number of particles in the Mod_90˚ scheme is smaller than in the Org_0˚ scheme when particle sources increase. This is because the Org_0˚ scheme has only one exhaust outlet near the patient's head, while the Mod_90˚ scheme is positioned between two exhaust outlets. Hence, it is crucial to take into account the patient's position concerning the placement of exhaust outlets. According to the observation results of CO 2 and DPM concentrations and the number of particles per total volume inside the investigated operating room, the modified position at 90˚ is the best patient location on the surgical table with the lowest number of particles and minimum concentrations in reducing SSIs. These lowest amounts of existing particles and minimum concentrations can help achieve a safe, clean zone in the operating room, especially regarding SSI issues.

Comparison of the number of particles per total volume at only the patient model and two staff including the patient.

Investigation of contaminant effect according to the surgical staff

After determining the best patient position on the surgical table to be the modified position at 90˚, CO 2 concentrations are calculated for eight configurations. These calculations consider different numbers of surgical staff and various supply velocities (0.36 m/s, 0.53 m/s, 0.75 m/s, and 0.82 m/s) that can get room pressures of (2.58 Pa, 5.58 Pa, 5.89, 11.27 Pa, and 12.36 Pa) as illustrated in Fig.  12 . These eight configurations are denoted as follows: only patient, two staffs, four staffs, six staffs, eight staffs_M1, eight staffs_M2, ten staffs_M1, and ten staffs_M2, including the patient, as shown in Fig.  3 . At a supply velocity of 0.36 m/s, CO 2 concentrations increase to over 1000 ppm when ten healthcare staff are inside the operating room, and they approach 1000 ppm when eight staff are present. This indicates that the operating room lacks sufficient air exchange when the staff count exceeds eight people, particularly when the supply inlet velocity is 0.36 m/s, and the room pressure is 2.58 Pa. However, the operating room maintains a good air exchange level, with CO 2 concentrations remaining below 1000 ppm in the indoor environment, even when ten staff members are present, provided the supply velocity increases with high positive room pressure. Hence, supply inlet velocity is a critical parameter for achieving a favorable indoor air environment, as it directly impacts room pressure. This relationship is evident as room pressure increases significantly, ranging from 2.5 to 12.36 Pa, with variations in supply inlet velocity from 0.36 to 0.82 m/s.

CO 2 concentration at eight configurations with different velocities, 0.36 m/s, 0.53 m/s, 0.56 m/s, 0.75 m/s, and 0.82 m/s.

Furthermore, the CO 2 concentration decay in the eight staff_M1 configuration exhibits an unstable effect across all velocity variations. This instability arises because the surgical staff is positioned between the patient and exhaust outlet 2 and outlet 3 , which can disrupt airflow and create turbulent effects inside the operating room. Figure S5 represents the turbulent formation around the patient mouth and head due to the positioning of the surgical staff. Despite small turbulence occurring near the patient's head in all eight configurations, there is high turbulence from the mouth area to the patient's head area in the eight staff_M1 configuration model. This high turbulence can increase the SSI problem because contaminants get trapped within this turbulent flow before leaving the exhaust outlets. Therefore, the positioning of surgical staff is an important parameter in reducing the SSI issue.

The operating area requires cleanliness to the highest possible standard, with a requirement of 10,000 class and a maximum of three distinct particle sizes permitted inside the room. Therefore, in this study, three different particle sizes such as 0.5 µm, 1 µm, and 5 µm together are used for the calculation of aerosol number of particles from the breathing and speaking model. The maximum allowable particles are also different as 352,000/m 3 , 83,200/m 3 , and 2,930/m 3 according to the standards. All the particle numbers are recorded until 900 s based on the volume of one cubic meter inside the operating room. As indicated in Fig.  13 , the investigated operating room can maintain particle levels below the acceptable maximum per cubic meter, even when occupied by ten healthcare workers, across all particle sizes (0.5 µm, 1 µm, and 5 µm). The particle deposition rate decreases as the supply velocity increases in all configurations except for one, such as eight staff_M1, as shown in Fig.  13 (a) and (b). In the eight staff_M1 configuration, two surgical staff members are standing near the patient’s head, which disrupts the extraction of aerosol particles due to the high turbulence airflow between outlet 2 and outlet 3 as mentioned earlier in Figure S5 .

Comparison of the number of particles from eight configurations with various velocities and particle diameters: ( a ) breathing model and ( b ) speaking model.

In addition, there are two effects according to Brownian motion and Saffman’s lift forces acting on the particles based on their particle size. When the particle is less than 1 µm, high Brownian diffusion can be caused 47 and Saffman’s lift force can be increased if the sub-particles are between 0.1 µm and 1 µm 25 , 48 . This high Brownian diffusion can result in greater net movement of particles from their starting point, and Saffman’s lift force also causes increased acceleration, moving the particles more effectively. Therefore, the total number of particles per cubic meter is larger at the smallest particle diameter of 0.5 µm compared to the other two particle sizes of 1 µm and 5 µm. According to CO 2 concentration and the number of particle depositions, the positions of the surgical staff and exhaust outlets are also important parameters for removing contaminant aerosol particles.

Investigation of particle dispersion according to without and with mask

A surgical face mask is required for entry into the operating room in most contemporary hospitals. Therefore, this research studies the effect of mask usage on airborne bacterial counts near the surgery site by comparing masked and unmasked models, as shown in Fig.  14 . The comparison of the particle dispersions from eight configurations (i-viii) while wearing and not wearing a mask in the breathing model, with a particle diameter of 0.5 µm, supply velocity of 0.56 m/s, and room pressure of 5.89 Pa as described in Fig.  15 (a) and (b). In Fig.  15 , the red-colored highlight represents the crucial surgical area on the operating table. This area needs to be kept clean to reduce the risk of infection with open wounds. Therefore, the particle-releasing effect is tracked from 1 to 7 s to investigate the initial particle movement.

Masked and unmasked models of surgical staff.

Top views of the particle dispersion of eight different configurations in the investigated operating room with a diameter of 0.5 µm at 7 s: ( a ) while not wearing the mask and ( b ) while wearing the mask.

All the particles moved outward from the surgical table, originating from the contaminant sources of the patient and surgical staff, without dispersing near the patient’s body, as shown in Fig.  15 . Similarly, the movement of all the particles from the mouths of the patient and surgical staff was directed upward and away from the surgical table, as illustrated in Figure S6 . This clean surgical area is maintained due to the direct airflow pattern from the supply inlet area to the operating area. In summary, it was noted that the investigated operating room could safely accommodate up to ten staff while maintaining acceptable cleanliness and a good air change rate, provided the supply velocity is above 0.56 m/s and the room pressure is 5.89 Pa. Although wearing a mask can create a cleaner area by controlling particle dispersion around the operating table compared to unmasked operations, it does not significantly influence the dispersion route of exhaled particles, as shown in Fig.  15 (a) and (b). Therefore, it can be observed that wearing a mask is not an effective solution for reducing surgical site infections. This finding is supported by previous research, which shows no difference in SSIs between surgeries performed with and without masks 60 , 61 , 62 , 63 , 64 .

Energy consumption

In the HVAC system, the AHU fan is the most important component and a significant energy consumer 65 , 66 . It can use approximately 40% of all electricity in HVAC systems 67 . Therefore, the energy consumption is mainly calculated by multiplying the volume flow rate and pressure difference from the supply fan. The volume flow rate is divided by the total room volume to get the air change rate, ACH of the operating room. The supply surface area is multiplied by the supply velocity to approach the relevant volume flow rate into the OR. In Fig.  16 , the parameters of volume flow rate, ACH, and room pressure are directly proportional to the supply velocity. The power consumption is maximum at the supply velocity between 0.53 m/s and 0.75 m/s; thereafter, the power decreases even as the velocity increases. As an obvious result, ACH is the main parameter in the clean room design, and it can be maintained by adjusting supply velocity. In addition, the average room temperature varies around 22˚C inside the OR with all the different airflow rates, which is under the acceptable temperature limit.

Relation of volume flow rate, ACH, room pressure, and power consumption according to the supply velocity in the ventilation system of the investigated OR.

The maximum operating air volume and fan speed, 1.32 m 3 /s and 4,100 rpm respectively, are determined based on the selected fan type for the operating room, with the actual operating point in the installation shown in Fig.  17 . The investigated operating room operates beyond the fan's operating point at high velocities of 0.75 m/s and 0.82 m/s under current conditions. The high velocity effect can result in overpressures of 11.27 Pa and 12.36 Pa, exceeding the desired design standard of 5 Pa. Although the investigated operating room is operating with the same power consumption near the fan operating point, it may result in higher volume flow rates of 1.78 m 3 /s and 1.95 m 3 /s. According to fan laws, the supply fan generates high airflow rates of 1.78 m 3 /s and 1.95 m 3 /s, requiring it to operate at 4,298 rpm and 4,577 rpm, respectively, which is beyond the maximum fan speed of 4,100 rpm. This high fan speed and overpressure effect can lead to unstable operation, reduced fan efficiency, and lifespan, as well as increased noise and vibration. A high volume airflow rate of 1.95 m 3 /s can reduce fan efficiency by about 7%, requiring the supply fan to operate at overspeed to supply the required amount of air. This can lead to increased vibration and noise in the ventilation system. Therefore, this overpressure effect needs to be maintained in the optimum condition and shows that the operating room needs to check the necessary supply velocity and room pressure for the relevant airflow rate of the supply fan.

Variation of power consumption with volume flow rate.

Improvement modification of the supply inlet area

To adjust the overpressure effect, modifications to the supply inlet area are considered to ensure operation within the operating point, taking into account other necessary parameters such as ACH, room pressure, CO 2 and DPM concentrations, and the maximum number of particles with varying numbers of surgical staff inside the OR. The original surface area of the operating room denoted as A 0 , is 2.36 m 2 , while the two modified surface areas, denoted as A 1 and A2, are 5.12 m 2 and 7.6 m 2 , as shown in Fig.  18 (a)-(c). When the supply area increases, high positive room pressure can be obtained with the low velocity effect as compared in Fig.  18 (d). In the original operating room with a supply surface area of A0, the inlet velocity should be set at 0.56 m/s, maintaining a room pressure of 5.89 Pa and achieving 35 ACH, to address the issue of the optimum overpressure effect and to preserve the lifespan and efficiency of the supply fan. Additionally, as the improved performance, the modified supply surface areas of A 1 and A 2 can operate with minimal velocity effects of 0.25 m/s and 0.17 m/s, respectively, maintaining room pressures of 5.55 Pa and 5.66 Pa, and achieving 34 ACH and 35 ACH. This indicates that the modified operating rooms can maintain acceptable cleanliness levels without imposing any harmful effects on the supply fan. Moreover, the larger size of the supply inlet area can provide a cleaner environment not only around the patient's body in the surgical area but also for the surgical staff standing around the surgical table as shown in Figure S7 of the airflow pathlines. This cleaner zone tends to enhance the performance of surgical staff by providing a safer working environment, thereby reducing SSI cases and extending the life span of the operating room’s ventilation system through adjustments in minimum ACH, power consumption, and optimal room pressure.

Modification of the operating room: ( a ) original supply surface area, A 0 ; modified supply surface area, ( b ) A 1 , ( c ) A 2 and ( d ) variation of supply velocity and room pressure according to the supply area.

Conclusions

In this study, the transient simulation of the positive pressurized operating room has been carried out by using the standard k- \(\upvarepsilon \) model, species transport, and Lagrangian approach for the air quality, BCP deposition, and CO 2 concentration in different schemes. The following conclusions are made in light of the results that have been presented:

The numerical calculations are in successful agreement with the measurement tests of supply velocity, exhaust outlet velocity, and number of particles for the investigated operating room.

The concentrations of CO 2 and DPM directly depend on the supply flow rates and room pressure. Four different schemes are classified to determine the optimal position for the patient on the surgical table. The modified position at 90˚ is the best position with the lowest contaminant concentrations compared with others. This approach tends to show the position of the patient should be adjusted according to the arrangement of exhaust outlets. Therefore, the patient's position on the operating table is the first main parameter to reduce SSIs due to the lowest contaminant effects.

The different durations to achieve minimum stabilized CO 2 concentration levels tend to show that the number of surgical staff inside the OR is the second important parameter to reduce SSIs. Hence, eight configurations are analyzed according to different numbers of surgical staff with different supply velocities and room pressure ranges of 0.36—0.82 m/s and 2.58—12.36 Pa, and particle diameters of 0.5 µm, 1 µm, and 5 µm. The current operating room can be performed by up to ten surgical staff present inside the room under acceptable cleanliness of a maximum number of aerosol particles per cubic meter if the supply velocity is greater than and equal to 0.53 m/s or 33 ACH.

The positioning of the surgical staff should be considered as the third essential parameter, which can be a barrier or turbulence airflow between the contaminant source and exhaust outlets. As a result, the SSI issue can be reduced by adjusting the positioning of the surgical staff to avoid the effects of high turbulence.

According to the particle dispersion at 7 s, the patient can be in the safe clean environment surgical zone on the operating table. Similarly, there is no significant particle dispersion effect to reduce SSIs when the surgical staff is masked and unmasked during the operations.

The supply velocity and ACH are the remaining essential parameters, which are directly related to room positive pressure, volume airflow rate, temperature, and power consumption. The supply velocity of the investigated operating room should be maintained at 0.56 m/s with an optimum room pressure of 5.89 Pa and 35 ACH to adjust the overpressure for the problem of efficiency, and the life span of the supply fan.

It has been shown that modifying the supply area can enhance the performance of the operating room by creating a cleaner environment, which helps reduce SSI issues. This improvement is achieved through maintaining low velocity and high positive room pressure, without impacting the efficiency or lifespan of the supply fan.

This present research tends to improve understanding of how ventilation air and contaminant concentrations are dispersed in the operating room and awareness of the overpressure case that should be implemented in future design standards and guidelines for every positive pressure operating room.

Data availability

The original datasets for this study will be made available by the corresponding author upon reasonable request.

Abbreviations

Operating rooms

Bacteria-carrying particle

Surgical site infections

Discrete phase model

Computational fluid dynamics

U.S Department of health and human services

Vertical laminar flow type

Horizontal laminar flow type

Vertical laminar airflow ventilation

Horizontal laminar airflow ventilation

Temperature-controlled airflow ventilation

Carbon dioxide

Heating Ventilation and Air Conditioning

Air change rate

Exhaust air

Air handling unit

High-efficiency particulate air

Square meter [m 2 ]

Cubic meter [m 3 ]

Kilogram per second [kg/s]

Meter per second [m/s]

Celsius [˚C]

Pascal [Pa]

Parts per million [ppm]

Kilogram per cubic meter [kg/m 3 ]

Kilogram \(\times \) meter per square second [N]

Watt per square meter [W/m 2 ]

Cubic meter per second [m 3 /s]

Kilowatt [kW

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Acknowledgements

This work was supported by King Mongkut’s Institute of Technology Ladkrabang. We would like to acknowledge the Computer Simulation Engineering Laboratory, College of Advanced Manufacturing Innovation, KMITL for providing the computational facilities. We really appreciate PRINC HOSPITAL SUVARNABHUMI's permission to conduct the measuring test.

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Oo, G.M., Kotmool, K. & Mongkolwongrojn, M. Case Study on the design optimization of the positive pressure operating room. Sci Rep 14 , 18671 (2024). https://doi.org/10.1038/s41598-024-69155-3

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Converting Lawns Into Diverse Landscapes: Case Studies

A resident of Harford County replaced portions of the lawn with native plants to increase native habitat and beauty in the landscape.

Growing and maintaining turf in Maryland is challenging  and resource-intensive. Replacing grass areas with locally adapted  native plants and landscaping is an effective way to make your property beautiful and better for the environment.

Take a look at the examples below of Maryland residents who reduced their lawns, solved water runoff problems, increased enjoyment of their property, and reduced the negative impact of lawn maintenance on climate change .

Converting lawn strip into a pollinator garden

Lawn before it was removed

Early spring this year - one year after the garden was planted

Summer view of garden showing native bee balm in bloom. The bees loved it. Also showing the certification signs for the garden.

Garden in September with asters about to bloom. Phlox and goldenrod in bloom.

View of the garden from the other direction with goldenrod in bloom to provide nectar for migrating butterflies as well as other pollinators.

Landscape design sketch

The main plants used in this garden:

• Asclepias tuberosa (butterfly weed)
• Asclepias syriaca (common milkweed)
• Aster 'October Skies'
• Solidago 'Fireworks' (goldenrod)
• Nepeta 'Walker's low' (catmint)
• Allium Millennium
• Monarda 'Bradburiana' (bee balm)'
• Caryopteris 'Golden Sunshine'
• Echinacea (purple coneflowers)
• Sisyrinchium angustifolium (Blue eyed grass)
• Oenthera (evening primrose) for ground cover
• Phlox subulata

Lessons learned:

"We did the entire garden ourselves. I bought plugs of many of the plants to reduce the cost. I planted in drifts so the pollinators would have easy access to them. The bees love the catmint and allium millennium although neither are native. The garden has required little maintenance. However, it has been a struggle to resist the temptation to deadhead taller plants like the coneflowers and milkweed to make the garden look better. I have to tell myself the goldfinches love the coneflower seeds and the monarch caterpillars are still on the milkweed. You have to view the garden from the insects’ point of view rather than the humans’ point of view."

- Diane Mitchell, Harford County

Townhouse property converted to native and edible plantings

Front yard before

Backyard before

Front yard after

Backyard after

"Once only turf, mulch, and non-native plants, I converted my small townhouse front and back yards to native and edible plantings over three years. The garden is a Certified Wildlife Habitat and was featured as a stop on the first annual Green Team Urbana garden tour (a group I co-founded to help restore the land in our heavily developed area). I'm an enthusiastic amateur gardener and currently a Certified Master Naturalist intern in Frederick County."

Plant list:

"Black- and brown-eyed Susans, tall phlox, rattlesnake master, bee balm, blanket flower, goldenrod, aster, coral honeysuckle, American wisteria, purple coneflower, anise hyssop, sunflowers, mountain mint, false sunflower. Various herbs, vegetables, and berries. I used marigolds, catmint, and alliums as low-profile "edging" around taller native plants and transplanted violets into my garden beds as ground cover."

"This was a DIY project. I started by marking out garden beds and layering them with cardboard and compost, then cutting holes in the cardboard and planting plugs. I found gardens or pieces of gardens I liked on Pinterest and then recreated them with native plants. (I'm a particular fan of English cottage gardens, and the look is easy to recreate with the lush, organic, slightly messy look of native plants.) I tried and failed a lot, but I dug in and got my hands dirty and wasn't afraid to fail. Some plants will surprise you; let them. Don't be afraid to start. You can always dig up or move plants later on."

-Bethany Adams, Frederick County

Increasing plant diversity along the sidewalk

Beginning of project: using a pickaxe, shovel and rake, I physically removed zoysia grass, being sure to remove all roots, but retaining soil.

Using a flexible hose to define the curving shape of the new garden, I finalized the design and edged the border with the remaining lawn. Remember to call Miss Utility about underground utilities!

Using leftover bricks from previous projects, I installed brick edging along the sidewalk. This will help retain water, soil, and mulch until the new garden is well established.

After enriching the new plot with compost, it was time for transplanting. I moved creeping phlox ( Phlox stolonoifera ), Siberian iris ( Iris sibirica ), a rose bush, black-eyed susan ( Rudbeckia hirta ), and a large mangave ( Mangave Macho Mocha).

The final steps included installing new plants (mostly native) and shrubs, and mulching. The new plants included asters ( Aster laevis ‘Bluebird’), dogwood ( Cornus stolonoifera Farrow), yarrow ( Achillea Summer Sangria), and beardtongue ( Penstemon Husker red). Mulching and watering sufficiently to get plants established are the final steps.

"In 2021, I decided to reduce the lawn area and increase plant diversity in our front yard bordering the sidewalk, mirroring the shape of the garden on the south side of the walkway. Considerations included reducing runoff from hard surfaces, introducing more native plants and shrubs, and diversity of color, foliage, and blooming season of transplanted and newly-purchased plants."

Lessons Learned:

"This was a DIY project, and it was labor-intensive. Removing all grass and roots was strenuous work. Half of the plants installed were transplants from other locations on the property. Purchased plants and mulch cost approximately $225."

-Larry Clements, Prince George's County

Rain garden solved a runoff problem

August 2015 Rain Garden “Before”

September 2015 Rain Garden

October 2015 (downspout through berm and the rain garden planted)

May 2021 “After” (Spring bloom in the rain garden)

July 2021 “After” (Summer bloom in the rain garden)

Debbie Sheppard from Prince George's County comments:

We were looking to solve the problem of rainwater runoff coming from the direction of our neighbor's yard. The water would sit against our home's foundation and puddle for days making it impossible to walk around two sides of the house. We decided to install a deep rain garden to catch the runoff. With a simple phone call to the Prince George’s County Rain Check Rebate , they quickly had someone come visit our property and go over any questions about the program. By doing all of the digging (my husband with a small backhoe and me with a shovel and wheelbarrow) and completing the install, we were able to accomplish the project at a low cost. It was a great "excuse" to make a fun design and shop for the appropriate plants! We now enjoy the ability to walk around our yard after a rain. We have a swing right next to the rain garden where we drink our coffee. It is a delight to take in the beauty of the flowers, plants, birds, and pollinators!

Plants that worked best over the years:

Golden ragwort (Packera aurea) - fantastic, quick, and dense ground cover in center of rain garden

Cardinal flower (Lobelia cardinalis) - tremendous self sower, really throws up plants everywhere

Creeping phlox ( Phlox stolonifera) - absolutely beautiful on the berm 

Bowma’s root (Gillenia trifoliata) - Always looks tidy, no pest or disease problems 

Ninebark ( Physocarpus opulifolius) - beautiful and healthy 

Purple coneflower (Echinacea purpurea) - flowers

Blazing star (Liatris spicata ‘Kobold’) - beautiful texture and bloom

White Wood Aster ( Eurybia divaricata) - dry shade

Tips for others who want to do a similar project?

Be ready to weed for a few years to allow for plants to grow in. Stay on top of weeding, otherwise you will have a field and not a planned garden. Did I mention that you will need to love weeding?! Wow - what a learning opportunity! So fulfilling!

Turning lawn into a meadow

Backyard original: I dug out dozens of cinder blocks and pavers, put in trenches with hugelkultur backfill. The area to the left is an old garage pad of concrete with 6-8” of soil on top… hopefully will remove this over the winter. I have many photos of the before, during, and after. When we moved in there was almost entirely grass. Now we have native plants everywhere!

I installed sections from a mature cherry tree to add some terracing to slow down runoff. I’ve planted with 90% native plants and a few high value non-natives. I have a toddler and dog so the yard has to be “play friendly.”

Front yard has Honeyvine milkweed, blueberries, little bluestem, joe pye, my iron weed, helianthus Maximilian, giant yellow hyssop, winterberry, echinacea, and other natives. I’ve been cultivating violets, native plantain, and other walkable green mulches to use as edging around the fence. I’ve documented the “hell strip” next to the side wall and noted what grows well and what requires lots of maintenance. Next spring I plan to start removing all the plants and replacing them with native carex, lyreleaf sage, and native plantain.

Front yard has a child’s playhouse and several enormous cherry logs that act as a stage. This side has aromatic asters, Solidago altissima, and other native plants. I’ve trained a native clematis to grow up the side and over the roof of the little house to provide summer shade. On the back corner (behind the non native magnolia), is an enormous pokeweed I’ve pruned to grow along with native plants and tithonia… they’re over 6’ now.

Still working on eliminating non-native, invasive honeysuckle, mulberry, and others, but this area has a log “fence” over a swale and then is planted with yarrow, liatris, and blue lobelia. The logs are gorgeous in cooler weather when the moss and fungi come out. We’ve seen two new species of woodpecker, had Orioles fledge two chicks, and a resident group of bluebirds visit the enormous American holly in the back.

"I have over 100 native plants including 7 varieties of asters, 4 goldenrod, and 2 perennial sunflowers. My plantings are based on Dr. Tallamy’s research into keystone plants plus additional shrubs, understory trees, and perennials that are host plants. I’ve kept detailed lists of all the plants I’ve put in."

- Amy Sawyer, Prince George's County

Calvert County meadow added along driveway area

Beginning of meadow garden with solarization.

We put in an extension to our driveway in order to have the driveway be circular. This created a "lawn" from a previous hayfield. In the Fall of 2020 I started a narrow, curved meadow garden down the middle of the circular driveway with native grasses and forbs. Photo shows a small patch with solarization. This Fall I am filling in either side of that narrow meadow so that it fills up nearly the whole space created with a circular driveway.

First season with planted meadow

This is the view of the meadow in the Fall of 2021. I used Little Bluestem ( Schizachyrium scoparium "MinnBlueA" and Hairawn muhly (Muhlenbergia capillaris) for the grasses as they don't get very tall (2'-3').

Meadow island

This photo shows a border (planted 2018) created to reduce lawn. I initially used Canadian Wild Rye and Big Bluestem (Andropogan gerardii) and various forbs. The Canadian Wild Rye started to take over the forbs and I removed it after two years.

The main plants used in this design:

"I used perennial black-eyed Susans, butterfly weed, native grasses as discussed in photos, goldenrod, bee balm, liatris and many other natives. I used zinnias for continuous color."

"I learned that I really need to cut my tall grasses down early in the season as they get so tall that they fall over and must be staked."

Sidewalk strip grass replacement

Master Gardener Beth Blum Spiker got tired of mowing the strip along the sidewalk.

Lawn replaced between sidewalk and street

A large portion of the lawn was replaced. Now the entire yard can be mowed in 17 minutes! 

The new plants look great in bloom.

Landscaping adjacent to the house

The landscaping in front of the house was also expanded.

Master Gardener Beth Spiker got tired of mowing the strip along the sidewalk. She replaced everything she didn’t like when she mowed, and now she can mow the entire yard in 17 minutes!

Lawn replacement along the waterfront

A section of lawn around the stairway was replaced with new plants.

A second view of the newly-planted feature looking towards the water.

As the plants mature, they fill in the space.

Gardens like this with native plants should reduce runoff into our waterways.

“ When we bought our house there were three trees, one rhododendron, three camellias, a dozen or so azaleas, and a similar number of boxwood. After 5 years of owning the house, I converted a portion of it to a nice collection of all types of plants. We had Adkins Arboretum help us with a garden design using native plants, and the non-natives were mostly given to us by friends from their yards.” - Dora Jean Hanna, Master Gardener

Desert area to native plant meadow

The backyard was a desert after the installation of the ground loop system. The ground was hard, dry, full of clay and rocks - just right for native plants!

I bought very few plants. I was able to transplant coneflowers and black-eyed-Susans from other gardens. Friends also gave me many plants. I knew I wanted grasses and movement in the garden so I sowed little bluestem and prairie dropseed grasses in jiffy cups and tended them very carefully. If I had sown seeds directly in the ground, they would have been lost among the emerging weeds.

Because the grass plugs were small, I put chicken wire cages around each one for protection from rabbits, groundhogs, and deer. I found a few plants with teeth marks, but for the most part, the animals left the meadow alone. I had plenty of other food that probably interested them.

Each time I planted a grass or perennial, I mulched the surrounding area. After a native garden is established, watering is not necessary. When starting a meadow, the gardener has to baby the plants. I watered a great deal last summer. There were some very hot, dry days. This year I did not water the meadow at all.

It was unbelievable to me that I was able to establish this mini meadow in one season. It is true that using native plants in hostile territory is the path to take. I did not amend the soil, but I did put a little compost from my compost pile into each planting hole. This meadow is the first thing I look at every morning when I walk onto the back patio. It is my last view every evening. On windy days the grasses dance just as I had hoped they would do.

"After my husband and I put in a ground loop heating and air conditioning system, the backyard was a desert. Because I had read Doug Tallamy's book Nature's Best Hope , I envisioned a small meadow. I consulted friends, researched online, read books, and visited Longwood Gardens in Pennsylvania and Mt. Cuba in Delaware. I knew what I wanted to do."

-Harford County gardener

Bay-Wise landscape

From above, you can see the property is almost surrounded by plants other than turf.

The only turf George kept on his property, other than pathways through his landscapes, is this small maintained "lawn room" close to his home and pool.

A narrow turf pathway winds between native plant landscaping.

The landscape looks great at sunset.

Curved lines in the landscape create interest. They pull you through the garden to see what's around the corner or the curve.

George's property is an official Bay-Wise demonstration landscape.

Maryland Master Gardener George Yurek kept a small “lawn room” close to his home and pool. Around the rest of the property, he created a Bay-Wise landscape by adding a variety of trees, grasses, shrubs, and perennials. Minimal lawn strips are used as walkways throughout the landscape.

Sod to native plant conversion

Before adding garden landscaping the yard contained mostly grass.

Newspaper was laid down in areas to smother the grass.

Mulch is laid over newspaper and new plants are planted.

This is the yard as it is now.

Howard County Master Gardener Molly McElwee laid sod at her new home in 2006. Then she started adding gardens, continuing with an expansion in 2016 using the “lasagna method” to smother grass and prepare the planting areas. “We have a very heavy emphasis on natives, especially host plants and plants beneficial to all sorts of wildlife. We are leaving some grass for pathways through the garden!”

Related information

The Challenge of Growing a Lawn in Maryland

Lawn (Turfgrass) Removal Methods

Lawn Alternatives

Recommended Native Plants for Maryland

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Harris Chooses Walz

A guide to the career, politics and sudden stardom of gov. tim walz of minnesota, now vice president kamala harris’s running mate..

This transcript was created using speech recognition software. While it has been reviewed by human transcribers, it may contain errors. Please review the episode audio before quoting from this transcript and email [email protected] with any questions.

Hey, it’s Michael. Before we get started, I want to tell you about another show made by “The New York Times” that pairs perfectly with “The Daily.” It’s called “The Headlines.” It’s a show hosted by my colleague, Tracy Mumford, that quickly catches you up on the day’s top stories and features insights from “The Times” reporters who are covering them, all in about 10 minutes or less.

So if you like “The Daily”— and if you’re listening, I have to assume you do — I hope that means you’re going to “The Headlines” as well. You can now find “The Headlines” wherever you get your podcasts. So find it, subscribe to it, and thank you. And now, here’s today’s “Daily.”

From “The New York Times,” I’m Michael Barbaro. This is “The Daily.”

[MUSIC PLAYING]

Today, the story of how a little known Midwestern governor became Kamala Harris’s choice for a running mate. My colleague Ernesto Londoño walks us through the career, politics, and sudden stardom of Governor Tim Walz of Minnesota.

It’s Wednesday, August 7.

Ernesto, over the past few days, we watched Vice President Harris bring the final three contenders for her running mate to her house in Washington, DC, for a set of in-person interviews. And then we watched as she seemed to narrow her pool of choices down to a final two — the governor of Pennsylvania, Josh Shapiro, and the governor of Minnesota, Tim Walz. And now, of course, we know that she has made her choice. What has she told us about her campaign strategy, the way she views this race, in ultimately choosing Tim Walz?

Michael, I think what the choice tells us is that Kamala Harris was drawn to two qualities that Governor Walz brings to the table. And what’s interesting is they may seem to be in tension. For starters, here’s the ultimate everyday man, somebody who grew up in a small town in Middle America, served in the National Guard, was a high school teacher, a football coach, very plain-spoken, goes to campaign events wearing T-shirts and baseball caps, is a gun owner and very proud about it. He sort of embodies the Midwest.

And she clearly thinks that that is going to bring the kind of moderate, white, working class voters that the campaign needs in swing states to come to them, to make this feel like a balanced ticket and something that will give her enough of the crucial votes to defeat Donald Trump in the fall.

On the other hand, as governor, he passed a slew of pretty progressive legislation in the past couple of years, everything from abortion rights to gun control. So these things are likely to appeal to bread and butter Democrats.

But the question is, when voters have examined these two facets of Tim Walz, may it bring them enough enthusiasm from the base and enough undecided voters that the campaign desperately needs, or at some point, do these two aspects of him start canceling each other out?

Right. In short, you’re saying Harris is betting on a dual appeal from Walz to two essential constituencies, but the risk is that the appeal to one of them is just much, much greater than to the other.

Right. You could definitely see a scenario where voters, once they’ve examined Tim Walz’s story and legacy, may conclude that both of these candidates are quite liberal.

OK, so tell us the story of Tim Walz, a story that I think a lot of us don’t know because we really don’t know Walz all that well, and how he has come to embody these two qualities and that tension that you just described.

Michael, the origin story of Tim Walz’s political career is quite fascinating.

He and his wife were teachers in a small city south of Minneapolis. And in 2004, when George W. Bush was running for re-election, Walz took a group of his students to a political rally in his hometown. They wanted to just see the president make his case. And a strange scuffle happened when they were trying to get in.

Well, one of the kids had a John Kerry sticker on his wallet. And this is where the individual says, well, you’re not going to be allowed to enter. You’ve been deemed a threat.

Apparently, one of the students had a sticker for Bush’s rival, John Kerry, on his wallet. And security officials at the rally didn’t want to let them in.

And I said, oh, it’s OK. They’re with me. And who are you? And I said, I’m Tim Walz. I’m their teacher here, and showed them my ID. And they said, well, you two have been deemed a threat to the president. And I said, well, that’s not true. And it kind of escalated.

And this really ticked off Tim Walz. He was really upset. There was a fight and a confrontation at the rally.

At this point in time, I’m kind of nervous. I’m getting arrested. So I’m like saying, well, I’m Teacher of the Year in Mankato. And they didn’t care about that. And it was kind of a sad epiphany moment, how it felt for people to be looked right through by people. These people didn’t see me. And this is happening.

And ultimately, he sort of walks away from this moment feeling really sick of the Bush administration, the politics of the day. And he turns around and volunteers for the Kerry campaign.

And then the more interested he becomes in politics in this era, he starts looking around his congressional district, and there’s a Republican who’s held the seat for many, many years. This was a largely rural district in southern Minnesota. And there’s no reason to believe that a newcomer to politics, somebody without a donor base, could make a run for this seat and win.

But Walz signs up for this weekend boot camp, where expert campaigners train newcomers who want to run for office. And he gets really enthused by the idea that he can pull it off. So he starts raising money with the support of an army of students who become so thrilled and energized by the prospect that their nerdy and kind geography teacher is making this uphill bid for a congressional race.

So his campaign staff is basically his former students.

That’s right. And he proves to be a formidable candidate. He draws a lot of attention to his experience in the classroom and as a coach.

When I coached football, these stands held about 3,000 people. That’s a lot. It’s also the number of American soldiers who have died fighting in Iraq.

He’s a very strong advocate for pulling out of the war in Iraq.

Serving right now are kids that I taught, coached, and trained to be soldiers. They deserve a plan for Iraq to govern itself, so they can come home.

And one thing that happens in the campaign that is really surprising to people is he comes out as being in favor of same-sex marriage. Now, it’s useful to remember that this is 2006, when the vast majority of Democrats, Democrats running for most elected office, were not ready to come out in favor of same-sex marriage.

And here’s a guy who’s new to politics, who’s trying to unseat a Republican who’s held on to his seat for more than 12 years, taking what appeared to be a reckless position on something. And when he was asked about it at the time, Tim Walz told a supporter, this just happens to be what I believe in. And I’d rather lose a race that I’ve ran being true and consistent to my values than try to run as somebody I’m not.

And of course, he wins.

Yes. To everybody’s surprise, he pulled it off.

So from the get-go, he shows a kind of maverick, “politics be damned” quality, taking stands that he knows may be unpopular among the voters he’s trying to win over. But he’s got some innate political gifts that are all making it work.

Yeah, I think that first campaign showed us that Tim Walz had real political chops. He was a very effective campaigner. And people really liked him. When he was knocking on doors, when he was introducing himself to voters, they saw him as somebody who was very genuine and who was admirable.

So once he gets elected in this conservative leaning district in Minnesota, what does he actually do in Congress?

In Congress, he develops a reputation for being somebody who can work across the aisle. And this is a period where Democrats and Republicans were deeply polarized over the Iraq War. He spends a lot of his time lobbying to expand benefits for veterans, so it’s easier for them to go to college after their service, and also becomes a leading voice in the quest to repeal Don’t Ask, Don’t Tell, the policy that prohibited openly gay servicemen from serving in uniform.

And he remained really popular. He easily won re-election five times. The last time he runs for his seat happens to be 2016, when President Trump wins his district by about 15 points.

And still, voters kept Tim Walz in office.

I think it’s important to note what you just said. Walz is distinguishing himself as a Democrat who can take some pretty progressive positions, as he did in that first campaign on gay rights, as he did with Don’t Ask, Don’t Tell, and keep winning in very Trump-friendly districts of his state.

That’s right. And as he’s serving his sixth term in office, he sets his sights on the governor’s mansion and decides to run for office in 2018. He wins that race easily. And early on, during his time as governor, the eyes of the world are on Minnesota after a police officer kills George Floyd. And what we see is massive looting and protests in Minneapolis.

Right, and remind us how Governor Walz handles that violence, those protests.

Yeah, I think that’s a crucial chapter in Tim Walz’s political career and one that will come under scrutiny in the days ahead.

After George Floyd was killed on a Monday —

People are upset, and they’re tired. And being Black in Minnesota already has a stigma and a mark on your back.

— protests took root in Minneapolis.

Y’all want to sit out here and shoot off your rubber bullets and tear gas.

And they got progressively larger and more violent.

There comes a point where the mayor and the police chief in Minneapolis plead for help. They ask the governor to send in the National Guard. And crucially, that request was not immediately heeded.

This is the third precinct here. There are fires burning to the left of it at the —

And at the height of the crisis, a police precinct building was abandoned.

There’s someone climbing up the wall right now, kicking the window in, trying to climb up the wall.

Because city officials grew concerned that protesters were about to overrun it and may attack the cops inside their own turf.

[EXPLOSIONS]

And the building is set on fire.

Right, a very memorable image. I can recall it happening in real-time.

Yeah, and in the days that followed, I think there were a lot of questions of why the governor didn’t send in troops earlier and whether a more muscular, decisive response could have averted some of the destruction that spread through the city.

And how does Walz end up explaining his decision not to send in the National Guard more quickly?

The governor and his administration have said that they were really, really dealing with an unprecedented challenge. And I think there was a concern that sending in troops into this really, really tense situation could have done more to escalate rather than pacify things on the street.

But in the weeks and months that followed, there were a lot of questions about Governor Walz’s leadership. And there were critics who said, during what may have been the most challenging week of his life, we saw a governor who was indecisive and who waited too long to send in resources that ultimately allowed the city to get to a semblance of order.

Right, and it feels like this is a moment that will almost assuredly be used against him by Donald Trump and JD Vance, the Republican ticket, which has made law and order so central to their message in this campaign.

Yeah, absolutely. And here in Minnesota, that was certainly a liability for him when he ran for re-election in 2022. But voters kept him in office, and he won that race handily. And not only did he win, but Democrats managed to flip the Senate and have full control of the legislature on his watch.

And that sets in motion one of the most productive legislative sessions in Minnesota history, where Tim Walz and his allies in the House and the Senate managed to pass a trove of really progressive legislation, oftentimes on a party vote.

Tell us about some of that legislation.

Well, Minnesota becomes the first state in the wake of the Supreme Court ending the constitutional right to abortion to actually codify this right under state statute. And they did a lot more stuff. They had a huge budget surplus, and they used that, for instance, to fund meals for all school children.

They managed to pass a couple of gun control laws that were very contentious. They gave the right to undocumented immigrants to get driver’s licenses. They legalized recreational marijuana. And finally, the governor takes a pretty bold stance on this issue of gender affirming care for transgender kids and teenagers, and says that Minnesota will be a safe haven for people who want that health care.

So, Ernesto, so how should we think about that blitz of legislation and the largely progressive tone of it, given the way that Walz had campaigned and succeeded up to that moment as somebody with such broad appeal across the political spectrum?

When the governor was asked whether this had been too much too quickly in terms of progressive legislation, his answer was that these were broadly popular policies, that these are issues Democrats had campaigned on. And here, Democrats had a window of opportunity where they were in control of the governor’s mansion and control of the House, the Senate, and that when you have political capital, you spend it.

But when you start listening to Republicans in Minnesota, they say, here’s a guy who campaigned on this mantra of “One Minnesota.” That was his campaign slogan. And he sort of came into office with this promise that he would govern in a bipartisan way, reach across the aisle.

But when they had all the votes they needed to pass their policies, Republicans felt that Walz was not bothering to bring them into the fold and to pass legislation that was going to be palatable to conservatives in the state. So I think people who once regarded him as a moderate now start seeing him as somebody who, when he had the power, acted in ways that were really progressive and liberal.

So at the height of his power, Governor Walz emerges as somebody who, when given a shot at getting done what he really wants to get done with a Democratic legislature, is a pretty progressive leader, even at the risk of being somewhat at odds with his earlier image as more moderate, because in his mind, enough people in the state are behind these policies.

Yeah, and I think he assumed that he had banked enough goodwill and that people across the state liked him enough to tolerate policies they may have disagreed with. And I think it’s safe to say, among the people who cover him here regularly, there was never any real hint that Tim Walz was eyeing a run for higher office. He’s not somebody who has written the kind of political memoir that oftentimes serves as a case of what you would bring to a national ticket or to the White House. And he seems pretty happy with a state job.

So it was a huge surprise when Tim Walz starts going viral through a string of cable news appearances right after President Biden drops out of the race, and the Democrats are scrambling to put Harris at the top of the ticket. And what becomes clear is that Walz is very forcefully auditioning for the role of vice president, and Vice President. Harris starts taking him very seriously.

We’ll be right back.

So, Ernesto, tell us about this cable news audition that Governor Walz undertakes over the past few weeks and how, ultimately, it seemed to help him land this job of being Harris’s running mate.

I think Walz does something really interesting, and that is that he says that Democrats shouldn’t be talking about Trump and Vance as existential threats. He kind of makes the case that Democrats have been in this state of fear and paralysis for too long, and that it’s not serving them well. So the word he latches onto is “weird.”

Well, it’s true. These guys are just weird.

It is. It is.

And they’re running for he-man women hater’s club or something. That’s what they go at. That’s not what people are interested in.

And I think one other thing we see in Walz is somebody who’s putting himself out there as a foil to JD Vance.

That angst that JD Vance talks about in “Hillbilly Elegy,” none of my hillbilly cousins went to Yale, and none of them went on to be venture capitalists or whatever. It’s not —

I think the case he’s making is that Tim Walz is a more authentic embodiment of small town values.

What I know is, is that people like JD Vance know nothing about small town America. My town had 400 people in it, 24 kids in my graduating class. 12 were cousins. And he gets it all wrong. It’s not about hate.

And behind the scenes, people from Tim Walz’s days on Capitol Hill start calling everybody they know in the Harris campaign and the Harris orbit and saying, here’s a guy who has executive experience as governor, but also somebody who has a really impressive record from his time on Capitol Hill and somebody who could be an asset in helping a Harris administration pass tough legislation. So you should take a hard look at this guy.

Which is, of course, exactly what Harris ends up doing. And I want to talk for a moment about how Harris announces Walz as her running mate on Tuesday morning. She did it in an Instagram message. And it felt like the way she did it very much embraced this idea that you raised earlier, Ernesto, that Walz contains these two appeals, one to the Democratic base, one to the white working class.

Harris specifically cites the work that Walz did with Republicans on infrastructure and then cites his work on gun control. She mentions that he was a football coach and the founder of the high school Gay Straight Alliance. She’s straddling these two versions of Walz.

But I want to linger on the idea for a moment of Walz’s vulnerabilities, because once he becomes Harris’s running mate, Harris and Walz are going to lose a fair amount of control over how they present him to the country, because he’s going to become the subject of very fierce attacks from the Republicans in this race. So talk about that for just a moment.

Yeah, I mean, it’s important to keep in mind that Governor Walz has never endured the scrutiny of a presidential race. So the questions he’s going to be asked and the way his record is going to be looked at is going to be different and sharper. I think the Harris campaign is billing him as, first and foremost, a fighter for the middle class. And I think that certainly will have some appeal.

But I think in coming days, there’s going to be a lot of attention drawn to parts of his record that may be unpopular with many voters. For instance, giving undocumented immigrants driver’s licenses, which Governor Walz championed. It’s likely to provide fodder for an attack ad.

The very dramatic footage of Minneapolis burning in 2020 is also something that I think people will be drawn to. And there’s going to be interest in reexamining what the governor did and what he could have done differently to avert the chaos.

And on Tuesday, we saw that the Trump campaign wasted no time in trying to define Tim Walz as soft on crime, permissive on immigration policy. And they also made clear they wanted to relitigate the era of George Floyd’s killing. And specifically, they want to try to tie him to the effort at the time to defund the police, which is a movement that Walz personally never endorsed.

So the Republican attack here will be pretty simple. Walz is liberal. Harris is liberal. So, in their efforts to speak to especially white working class and rural voters in swing states, the Trump campaign is going to say this is not the ticket for that group of voters. This is the ticket of burning police precincts and gun control. And of course, that may not be fair, but that’s very likely going to be the message over the next couple of months.

Right. I think there’s going to be effort to portray him as a radical liberal who has used his small town roots to put on this sort of veneer of being a moderate and a really sort of understanding and being part of the segments of the electorate that I think are critical in this election.

I want to speak for just a moment about the person Harris did not pick when she chose Walz because many Democrats had felt that Walz was a potentially too liberal seeming running mate for a candidate, Kamala Harris, who herself comes from a blue state and is caricatured by the Republicans as liberal herself.

And the person she didn’t choose was Governor Josh Shapiro of Pennsylvania, who was seen as having a huge appeal in that particular key swing state, but also presented risks of his own of alienating parts of the Democratic base with his well-documented support for Israel and his criticism of campus protesters. How should we think about the fact that, ultimately, Harris chose Walz over Shapiro?

Yeah, I think in the final stretch of this campaign to be the vice presidential pick, we started seeing a lot of acrimony in pockets of the Democratic base, drawing attention to the fact that Governor Shapiro could be divisive on Gaza, which has really sort of split the party in recent months.

So I think at the end of the day, they made a calculation that Tim Walz would be more of a unifying figure and would be somebody who would inspire and energize enough pockets of the electorate that they need, particularly in the Midwest, to make him the stronger and more exciting pick and somebody who wouldn’t force them to go back to defending and relitigating the Biden administration’s record on Israel and on the war in Gaza.

Right, and then, on Tuesday night, we got our first glimpse of Harris and Walz together on stage for the first time at a campaign rally. I’m curious, what struck you about their debut together.

Good evening, Philadelphia.

I think everybody was watching the opening scene of this rally to see what the chemistry between these two people was going to be like. And they both seemed giddy. They were literally, at times, bouncing with enthusiasm.

Since the day that I announced my candidacy, I set out to find a partner who can help build this brighter future.

So Pennsylvania, I’m here today because I found such a leader.

Governor Tim Walz of the great state of Minnesota.

They soon got down to business. And that business was how to define Tim Waltz for voters who don’t know him well.

To those who know him best, Tim is more than a governor.

And right off the bat, we saw that Kamala Harris really highlighted a lot of pieces of his pre-political career.

To his former high school football players, he was Coach.

She repeatedly called him Coach Walz, Mr. Walz, evoking his time in the classroom, and even used his military title from his days in the Army.

To his fellow veterans, he is Sergeant Major Walz.

And then when it came time for Tim Walz to introduce himself on this massive stage —

Welcome the next vice president of the United States, Tim Walz.

— he drew a lot of attention to his small town roots.

I was born in West Point, Nebraska. I lived in Butte, a small town of 400.

He said something that he said repeatedly recently in campaign appearances, which is —

In Minnesota, we respect our neighbors and their personal choices that they make. Even if we wouldn’t make the same choice for ourselves, there’s a golden rule — mind your own damn business.

The golden rule of small towns is you mind your own damn business, which is something he said in the context of his argument that Republicans have been limiting, rather than expanding, people’s rights. But he also drew attention to the fact that he’s a gun owner.

By the way, as you heard, I was one of the best shots in Congress. But in Minnesota, we believe in the Second Amendment, but we also believe in common sense gun violence laws.

And then when it came time to draw a sharp contrast with their opponents, Tim Walz said, these guys are phonies.

Donald Trump is not fighting for you or your family. He never sat at that kitchen table like the one I grew up at, wondering how we were going to pay the bills. He sat at his country club in Mar-a-Lago, wondering how he can cut taxes for his rich friends.

He said it’s actually people like me and Kamala Harris who come from humble origins and showed what is possible in America when you hail from a working class background, and you seize opportunities that were available to you.

Thank you, Philadelphia. Thank you, Vice President. God bless America.

So when it comes to this question of Walz’s dual identities and dual appeals, what did we learn on day one of this new Democratic ticket, do you think?

I think the campaign is trying to convey that these two facets of Tim Walz’s life are not mutually exclusive, that they don’t need to be in tension. They don’t cancel each other out. They’re both part of Tim Walz’s story. And I think that’s how they’re going to present him from now until Election Day.

Ernesto, thank you very much. We appreciate it.

It’s my pleasure, Michael.

Here’s what else you need to know today. On Tuesday, Hamas said that Yahya Sinwar, one of the masterminds behind the deadly October 7 attacks on Israel, had consolidated his power over the entire organization. Until now, Sinwar had held the title of Hamas’s leader in Gaza. But with the assassination of Hamas’s top political leader by Israel last week, Hamas said that Sinwar would take on that title as well. Sinwar remains a major target of Israel and is believed to have been hiding in tunnels underneath Gaza since October 7.

And the US Department of Justice has charged a Pakistani man with ties to Iran with trying to hire a hitman to assassinate political figures in the United States. The man recently traveled to the US and was arrested in New York last month. American authorities believe that his potential targets likely included former President Trump.

Today’s episode was produced by Alex Stern, Eric Krupke, and Olivia Natt. It was edited by Lisa Chow and Patricia Willens, contains original music by Pat McCusker and Marion Lozano, and was engineered by Alyssa Moxley. Our theme music is by Jim Brunberg and Ben Landsverk of Wonderly. Special thanks to Nick Pittman and Minnesota Public Radio.

That’s it for “The Daily.” I’m Michael Barbaro. See you tomorrow.

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Earlier this summer, few Democrats could have identified Gov. Tim Walz of Minnesota.

But, in a matter of weeks, Mr. Walz has garnered an enthusiastic following in his party, particularly among the liberals who cheer on his progressive policies. On Tuesday, Vice President Kamala Harris named him as her running mate. Ernesto Londoño, who reports for The Times from Minnesota, walks us through Mr. Walz’s career, politics and sudden stardom.

On today’s episode

Ernesto Londoño , a reporter for The Times based in Minnesota, covering news in the Midwest.

Background reading

Who is Tim Walz , Kamala Harris’s running mate?

Mr. Walz has faced criticism for his response to the George Floyd protests.

There are a lot of ways to listen to The Daily. Here’s how.

We aim to make transcripts available the next workday after an episode’s publication. You can find them at the top of the page.

The Daily is made by Rachel Quester, Lynsea Garrison, Clare Toeniskoetter, Paige Cowett, Michael Simon Johnson, Brad Fisher, Chris Wood, Jessica Cheung, Stella Tan, Alexandra Leigh Young, Lisa Chow, Eric Krupke, Marc Georges, Luke Vander Ploeg, M.J. Davis Lin, Dan Powell, Sydney Harper, Michael Benoist, Liz O. Baylen, Asthaa Chaturvedi, Rachelle Bonja, Diana Nguyen, Marion Lozano, Corey Schreppel, Rob Szypko, Elisheba Ittoop, Mooj Zadie, Patricia Willens, Rowan Niemisto, Jody Becker, Rikki Novetsky, Nina Feldman, Will Reid, Carlos Prieto, Ben Calhoun, Susan Lee, Lexie Diao, Mary Wilson, Alex Stern, Sophia Lanman, Shannon Lin, Diane Wong, Devon Taylor, Alyssa Moxley, Olivia Natt, Daniel Ramirez and Brendan Klinkenberg.

Our theme music is by Jim Brunberg and Ben Landsverk of Wonderly. Special thanks to Sam Dolnick, Paula Szuchman, Lisa Tobin, Larissa Anderson, Julia Simon, Sofia Milan, Mahima Chablani, Elizabeth Davis-Moorer, Jeffrey Miranda, Maddy Masiello, Isabella Anderson, Nina Lassam and Nick Pitman.

An earlier version of this episode misstated the subject that Walz’s wife taught. She taught English, not Social Studies.

How we handle corrections

Ernesto Londoño is a Times reporter based in Minnesota, covering news in the Midwest and drug use and counternarcotics policy. More about Ernesto Londoño

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