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ISU professor co-authors first natural ventilation design guide specifically for architects

June 09, 2015


Architecture Associate Professor Ulrike Passe with an advance copy of her new book, "Designing Spaces for Natural Ventilation: An Architect's Guide."

AMES, Iowa — Opening windows and allowing air to flow through is often the optimal method for cooling spaces, as well as the most cost effective. It can also be a delight to feel the breeze on your skin and smell the fresh scents wafting in. But many of us live and work in places designed for mechanical conditioning and ventilation—with inoperable or inadequate windows.

In an era of climate change, increasing energy costs and an emphasis on renewable resources, an Iowa State University architecture professor and a mechanical engineering colleague at Virginia Polytechnic Institute and State University, Blacksburg, think naturally ventilated buildings will become essential for human comfort and energy efficiency.

And they have just published a book intended to help architects design successfully naturally ventilated buildings.

"Designing Spaces for Natural Ventilation: An Architect's Guide," by Ulrike Passe and Francine Battaglia, was published by Routledge in April. The 342-page guide includes more than 260 color diagrams and photographs illustrating case studies and computational fluid dynamics (CFD) simulations. It provides scientific and architectural visualization tools to help architects develop ventilation strategies without an engineering background.

Architecture and energy
"When I first came to Iowa State in 2006, I set out to determine how the spatial composition of buildings supports the natural movement of air without a fan or air conditioning," said Passe, an associate professor of architecture in the College of Design and the director of the Center for Building Energy Research (CBER) at Iowa State. "I'm interested in how walls, openings, the width and the height of spaces affect the flow of air and energy."

Passe also sought to place more emphasis on architecture in the discussion about energy efficiency and renewable resources.

"Architecture as the well-tempered composition of space was about to be overcome by buildings consisting of compilations of boxes, as the tools to provide energy calculations were not—and still are not—able to account for the impact of complex spatial composition on energy flow in buildings," she said.

Passe, who as a practicing architect had designed a naturally ventilated home for her father outside of Hamburg, Germany, in the early 2000s, knew it was a physically and computationally challenging process. She sought to develop a set of strategies and tools architects could use to more easily design buildings that incorporate natural ventilation.

In 2007 Passe and Battaglia—who had been the CBER director at ISU before becoming a professor of mechanical engineering and the director of the Computational Research for Energy Systems and Transport (CREST) Laboratory at Virginia Tech—received a Boston Society of Architecture research grant to investigate the relationship between the spatial layout of building interiors and building energy consumption.

The study paired the techniques of architectural design analysis and CFD simulation to determine the effectiveness of buildings designed to be passively cooled or heated by circulating air without mechanical devices that consume energy derived from natural gas or electricity (known as natural ventilation or natural convection).

A critical step in the process was establishing a methodology to transfer a three-dimensional architectural computational model into a format that could be read by gridding software and used in CFD software, Passe said.

Air flow and turbulence model of the Vyborg/Viipuri Library designed by Alvar Aalto and completed in 1935. Model by Francine Battaglia and Preston Stoakes.

"The process we developed and first applied to the Vyborg/Viipuri Library by Alvar Aalto in Finland and the Esherick House by Louis Kahn in Philadelphia—both published in peer-reviewed papers in the international Building Simulation journal—not only visualized the movement of air in these complex spaces but validated case studies and thus laid the groundwork for the scientific research into natural ventilation and CFD simulation still conducted at CBER today," Passe said.

"These first CFD simulations provided the foundation for the analytical sections of the book."

Lessons from traditional architecture
Together with colleagues from mechanical engineering, materials science and engineering and electrical and computer engineering, Passe also is studying 200-year-old conical-domed, mud-brick houses in Harran, Turkey, which mediate a harsh external climate through their shape, construction materials and strategically placed ventilation openings in the walls and ceiling. The team is modeling heat transfer and air movement within the homes to understand what makes them effective, and analyzing the structures' natural dynamics to develop environmental control strategies for modern buildings to make them more energy efficient.

Traditional domed houses in Harran, Turkey. The shape, construction materials and strategically placed ventilation holes in the walls and ceiling help such homes stay cool and comfortable in hot weather. Photo by Ulrike Passe.

These projects and many others serve as case studies in the new "Designing Spaces for Natural Ventilation" guide.

"As soon as I knew I was doing the book I started looking for case studies and took photos wherever I could find naturally ventilated buildings that would demonstrate the concepts," Passe said.

A Routledge representative initially approached her to write a book on retrofitting existing buildings with energy-efficient, green technologies, but Passe proposed a publication geared toward helping architects design new buildings that incorporate such strategies from the start.

"This is the first-ever book written for architects solely on this subject," she said. "A lot of research has been published recently, but it's very engineering oriented with little focused specifically on how air moves through space and how space can be configured to facilitate air flow for passive heating and cooling. Much of the work referenced in this book—on climate, comfort, space and urban environments—has never before been compiled in one publication like this."

The secret to the Frank Lloyd Wright-designed Affleck House in Bloomington Hills, Illinois, lies in the horizontal window between the lower, open-air porch and the main living space. This allows for updraft air movement. Photo by Ulrike Passe.

Complex science made visual
Passe wrote the first two parts of the book—which cover theories related to physics, health, climate, history and thermal comfort, scientific and cultural background as well as parameters and case study project analysis—while on a faculty professional development leave from Iowa State in fall 2013.

Battaglia wrote the third part, which focuses on complex science made visual for architects and includes a thorough description of engineering computational method, in particular, computational fluid dynamics. Battaglia also provided all CFD simulations in the book based on joint research with Passe or other projects at Virginia Tech.

Passe received a Vernon Stone Faculty Grant through the ISU Department of Architecture in 2012 to support a team of undergraduate architecture students—Suncica Jasarovic, who graduated with a Bachelor of Architecture degree in 2014, and Shuaibu Kenchi and Matthew Darmour-Paul, who received BArch degrees in May—to create the diagrams for the book. Battaglia’s graduate research assistants created all of the CFD diagrams published in the book.

The authors analyzed the urban proportion of eight global cities and found that all had a very similar "street canyon" proportion despite a diverse height and width of blocks. Smaller urban entities like Ames had a much lower ratio, while areas like the Chicago loop had a much higher ratio.
This information can help architects understand what strategies can be applied in different urban contexts. Diagram by Ulrike Passe and Suncica Jasarovic.

"I was very determined to develop a consistent graphical language in the book. We developed diagrams to illustrate our own research, and we redrew a lot of diagrams adapted from many scientific references, which are often only presented in complex mathematical formulas and thus often difficult to understand with a non-engineering background," Passe said. "My goal was to encourage readers to engage with these rather complex physics concepts by providing a consistent graphic appearance to guide and support their understanding."

Passe also visited and photographed about 80 percent of the buildings highlighted in the book. Several images were provided by colleagues from around the world whom she met while presenting her research at national and international conferences and symposia.

In the book's foreword, British architect, educator and scholar Susan Roaf says, "Passe and Battaglia have set out systematically to provide a comprehensive introduction to the history, theory, and application of natural ventilation principles and practices in building design. They use language that architects are familiar with, and mathematical and computing tools that they can assimilate and apply, and provide clear directions on how to integrate the chosen air-flow and thermal storage systems into local climate contexts, ensuring that particular buildings in particular climates will be successful.

"This book provides a thorough architectural foundation from which to create the conditions necessary to design successfully naturally ventilated buildings that function well in practice."

For Passe, "that is the goal. This book is based on the understanding and inquiry of an architect and I really hope it communicates well to practicing architects, educators and students to support them in designing buildings not only with improved energy performance, but also with comfortable and delightful spaces."

Ulrike Passe, Architecture,
Heather Sauer, Design Communications, (515) 294-9289,