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Summer is the time for sunshine, but Americans have been getting a surplus of heat this summer, with millions of people across the Southeast recently facing a with heat indexes, or feels-like temperatures, reaching into triple digits.

According to Julian Wang, professor of architectural engineering at Penn State, these heat events show no sign of stopping and will require homebuilders and community organizations to brainstorm new strategies to stay cool during the summer.

Wang is the principal investigator on a project that seeks to develop and improve heat wave resistance in residential housing. Supported by a $1 million, three-year grant, Wang and his team are working with community organizations to develop a system that combines real-time environmental data, digital surveying and machine learning techniques to pinpoint the vulnerabilities leaving residents and their homes at risk during extreme weather events like heat waves.

In the following Q&A, Wang explained how the thermal resilience of housing goes beyond just keeping inhabitants cool, but improves sustainability, climate adaptation and overall community health.

Why are heat waves a growing concern for residential housing?

Heat waves are happening more often, lasting longer and getting hotter. For many old or poorly insulated homes, indoor temperatures can rise dangerously high. This both threatens residents' health, particularly older adults and children, but also exposes gaps in housing infrastructure that weren't designed for today's climate conditions.

Philadelphia, our field test location, is a good example—its housing stock and systems were historically designed for cold climates, not extreme heat. Now the city regularly faces heat wave emergencies and has launched multiple programs to help residents cope. Cities around the country find themselves in a similar situation now, underscoring the urgent need for housing solutions that address rising summer risks.

What are some examples of existing thermal resilience systems in homes? What are some new ideas your team is trying out?

Traditional ways of improving thermal resilience at scale, like insulation upgrades, storm windows, air sealing or cool roofing, can reduce heat indoors but are usually applied the same way to every home, or through simple rules based on home age or type. This one-size-fits-all approach often overlooks each home's unique vulnerabilities. Building on our previous research, our team is developing a more precise and cost-effective method that generates home-specific insights, while remaining scalable to the community or even city level.

Instead of relying on labor-intensive audits or costly instrumentation, we are testing how wearable sensors can capture both residents' personal responses to heat and their homes' physical vulnerability to external heat stress. Using advanced computational models, we can analyze just a couple of weeks of wearable sensor data to predict how residents and their homes will respond to heat waves.

These insights can guide the most effective and affordable improvements—such as targeted window films, exterior wall panel coatings or air-sealing fixes—tailored to each home's specific weaknesses.

These insights are also useful for community and city decision makers, who must recommend general improvements, while lacking the home-specific information needed to inform decisions. That is the key aim of our project—to link individual home features with the larger issue of thermal resilience and preparedness, so that both residents and decision makers can make smarter, targeted interventions.

What can homeowners do today to improve the thermal resilience of their house?

Simple steps can drastically reduce heat gain indoors and keep homes safer during heat waves, like sealing air leaks around windows and doors, adding shading or reflective films, improving insulation or using light-colored roof coatings. Doing this not only protects residents during heat waves but may also lower long-term energy bills by reducing the need for cooling and, in some cases, heating.

What is an 'envelope deficiency?' How would this impact the thermal resilience of a home?

An "envelope deficiency" refers to parts of a home's outer shell—walls, windows, roof or air sealing—that perform worse than what we typically see in comparable homes of similar size and location. Not all deficiencies are directly tied to thermal resistance or aligned with heat resilience goals, though. An exterior wall crack may be a deficiency if it creates air leaks or areas heat can enter the building, but only if that crack leads to a noticeable impact on the home's thermal resilience.

Why is it important for your optimizations for thermal resilience to be carbon efficient?

It's not enough to make homes more resistant to heat waves if the fixes themselves add to the carbon problem. Addressing this tradeoff is also a central goal of our parallel , which seeks to balance short-term thermal resilience and long-term sustainability when retrofitting homes with thermal resilience improvements. Our aim is to identify solutions that strengthen a home's resilience to heat, while also reducing energy use and greenhouse gas emissions.

Wang's collaborators on the project include Diane Berish, associate research professor in the Penn State College of Nursing; Emily Lucas, director of residential programs at Philadelphia Energy Authority; Andrew Niemynski, Built To Last program manager at Philadelphia Energy Authority; Markeyce Cogdell, housing and urban development project lead at Energy Coordinating Agency of Philadelphia; and Juliet Taliaferro, program manager at Energy Coordinating Agency of Philadelphia.