How to design for extreme temperatures

As the world veers towards warming 1.5 degrees Celsius and beyond, abnormal has become the new normal. Buildings designed and constructed today will face climatic conditions over their life that will be markedly different from what the built environment experienced in the past. Though architects cannot predict with 100% certainty what’s coming, it’s clear that our buildings need to be designed to survive and thrive through the new extreme conditions that they will be subject to.  

The recent past has already provided a glimpse of what we can expect. In 2017, Hurricane Harvey dropped 60 inches of rain, more than an average year's worth, near Houston, Texas. Simultaneously, major droughts are occuring with increased frequency in other parts of the world. Fundamentally, a hotter Earth means more energy to power extreme weather events. 

Extreme temperatures are an especially dangerous and increasingly common effect of climate change that nearly everyone has now lived through. Over the span of just four months in 2021, I personally experienced a historic ice storm in Texas that knocked out large portions of the utility grid and a string of 115 degree days caused by a heat dome over Portland, Oregon. In both of these events, many suffered and some people died because their buildings failed to provide shelter from the elements, the essential purpose of the built environment. 

As in times past, architects remain committed to the health, safety and welfare of the public. Given the state of today’s climate, design that effectively mitigates the risk of extreme temperatures is an essential part of this commitment. Fortunately, designing for extreme temperatures does not require any novel technology or knowledge, and buildings that effectively address this risk have the potential to be more energy efficient and more comfortable during everyday operations in more typical conditions.   

Prioritize the thermal enclosure

The most effective design strategy to address extreme temperature is a high-quality thermal enclosure. This means a combination of insulation, air sealing and appropriately sized windows (around 30% of wall area) to slow the flow of heat in or out of the building and maintain more stable indoor conditions.  

In colder climates, the value of a strongly insulated enclosure to maintain heat is already well recognized by architects. Thick insulation and tight air sealing is the norm where very cold winters are common, and these more thermally resistive buildings are more resilient to extreme temperatures, both hot and cold.  

In contrast, we pay less attention to insulation in warmer and more temperate climates. While   this might be fine the majority of the time, less thermally resistant enclosures pose real risks during the uncertainty of the future climate. Energy code, which determines minimum insulation, glazing, and air sealing values, is considered from the perspective of conserving energy on average over a year. Today it makes more sense to consider the thermal qualities of our buildings from the perspective of resilience. A quality enclosure will always conserve more energy and provide greater comfort, but it also offers the ability to safely endure the coming heat domes and arctic blasts of the 21st century.  

In addition to a strong thermal enclosure, orientation and shading are also effective design strategies for mitigating extreme temperature events, especially extreme heat. Solar heat gain will significantly contribute to a building’s indoor temperature and cooling load. If temperatures are above “normal” and the mechanical systems are unable to keep up, the addition of solar heat gain can push the indoor environment into unsafe conditions. Western exposure is often the culprit, and designs that limit glazing on the western side of the building will remain cooler and reduce A/C loads compared to buildings with significant western-facing glass. The ability to shield windows with shades, curtains, or shutters is also an effective strategy to keep heat out of a building whenever it’s warm, but especially during extreme heat events. 

The power of passive systems 

These strategies –  a quality enclosure, effective glazing area, operable windows, building orientation, and shading –  are all traditional passive design strategies that have been used for thousands of years to keep buildings comfortable. More recently, they have been used to effectively conserve energy usage for both heating and cooling purposes. It's not surprising that the same collection of strategies can be depended on to keep occupants safe from extreme temperatures, and this remains the case whether or not the power goes out. Power outages pose an additional challenge during extreme weather events, and architects need to consider and design for the possibility that a power outage will be coupled with extreme temperatures. Snow and ice storms have been known to bring down power lines, and during the summer, extreme heat can lead to brown outs if everyone is running their A/C on high and the utility is unable to provide adequate electrical capacity. Backup power is a useful solution in these situations, but it should not be relied on alone. Generators or batteries are most effective when coupled with appreciated passive design strategies.  

During the Texas ice storm of 2021, the temperature inside many homes quickly dropped below freezing when the power went out, resulting in frozen pipes and deaths from exposure. During the 2021 Portland heat wave, indoor temperatures spiked into the 100s in apartments that didn’t have cooling systems or effective operable windows, also resulting in deaths. In both cases, buildings with a quality thermal enclosure would have maintained indoor temperature at safe levels for longer periods of time. In the case of extreme heat, shades to block the daytime sun and windows that open to provide night cooling are simple and essential design strategies that can keep people safe.     

While the challenges of climate change are new, the most effective strategies have been around for as long as buildings have. To mitigate the risks of extreme temperatures when designing a building today, focus on passive systems. Choose a higher insulation value and more thermally resistant glazing than the code minimum recommends, and pay extra attention to air sealing to keep infiltration to an absolute minimum. Additionally, avoid unnecessary western glazing, provide effective shades, and ensure that windows can open enough to effectively cool and ventilate passively. Cooling systems are necessary in most locations that have not required cooling in the past, and backup power for life safety systems continues to be necessary, but it's important not to mistake active systems for an architectural design solution. The buildings of the future that effectively protect the heath, safety, and welfare of the public depend on the thoughtful application of age-old passive design strategies. 

Corey Squire, AIA is the Sustainability Director at Bora Architecture & Interior in Portland, Oregon, and a member of the American Institute of Architects' Strategic Council. He is the author of the recently-published book, People, Planet, Design: A Practical Guide to Realizing Architecture’s Potential.