UNIVERSITY PARK, Pa. — As the frequency and severity of both heat waves and extreme cold weather events increase across the United States, assessing how well a structure can handle extreme temperatures — known as thermal resilience — becomes critical, according to Penn State Associate Professor of Architectural Engineering Julian Wang. With a four-year, $500,000 National Science Foundation grant, a Penn State team led by Wang is developing a new holistic framework to understand the relationship between thermal resilience and sustainable design strategies for buildings and communities.

Wang and co-principal investigators Yuqing Hu, Penn State assistant professor of architectural engineering, and Guangqing Chi, Penn State professor of rural sociology, demography and public health sciences in the College of Agricultural Sciences, will develop the framework and then work with the city of Philadelphia and organizations for underserved communities to test their framework. 

According to Wang, building envelopes and indoor physical environments play vital roles in both thermal resilience and sustainability, even if the two paradigms can conflict. 

“Consider, for instance, low-emittance windows,” Wang said. “They have been widely accepted as an energy-saving design, but their typical strong solar reflection may reduce a building’s thermal resilience to cold events in winter and also exacerbate urban heat island effects in summer.”

Wang said that while other frameworks for assessing thermal resilience exist, they tend to focus on only heat waves and not extreme cold. 

“We consider it a heat wave or a cold wave if temperatures are outside the average maximum or minimum temperatures for more than three consecutive days,” Wang said. “We want to consider both situations, especially since many cities, like Philadelphia, have experienced both in recent years. The mechanisms to make a building responsive to both extreme cold or heat are fundamentally similar, and we want to quantify thermal resilience for both circumstances.” 

Another difference between the group’s proposed framework and existing thermal resilience models is that existing models tend to focus on some variables for thermal resilience at the expense of others, according to Wang. 

“In the past, when researchers tried to evaluate thermal resilience, some of them focused on the building itself, like the physics and the walls; some of them focused on the socio-demographic information, like household income, family size or age; some on communities, urban or rural; and some on human behaviors, like do you turn on the air conditioner or open the windows?” Wang said. “We're trying to integrate all the different angles from social factors to physics and human behaviors, as long as they have correlations to both thermal resilience and sustainability, to set up a multiple scale assessment system.”

The team will test commonly used materials and designs under extreme temperature events simulated in a walk-in weather chamber embedded with solar simulators. They will also incorporate wearable personal thermal comfort monitoring systems that were developed in their prior project, supported by Environmental Protection Agency, to evaluate how occupants’ sustainable behaviors impact the building thermal resilience.

Wang said the researchers will share the framework they develop with decision makers in Philadelphia, particularly those in the sustainability office with whom they are collaborating to gather the information to conduct on this project, to help them make quantitative decisions. Project collaborators based in China will further test the framework with datasets from different cities and communities.

According to Wang, this framework may help inform the best relief services for communities and specific buildings at higher risk of adverse impacts due to extreme temperatures, or it could provide insight for retrofitting buildings and future urban planning. 

“Eventually, we want to have a geographic information system function, so you could overlap this system with a map and click each community,” Wang said. “We could see overall in the city which parts are weaker and which parts are stronger when it comes to thermal resilience. By zooming in, we could also check each community and even each building to understand how likely each is to endure extreme temperatures.”

Ultimately, Wang said the researchers plan to make their framework publicly accessible so that urban planners, city officials and nonprofits that focus on relief during extreme temperatures can use it.