Over the past two decades, an increased frequency of extreme weather events has cost the U.S. more than $1 billion in infrastructure damages. This prompted the U.S. Department of Energy (DOE) to commission research to assess how increased energy efficiency can improve building resilience under extreme temperatures.
The study, Enhancing Resilience in Buildings Through Energy Efficiency, was prompted by DOE’s Building Technologies Office. Three research laboratories were tasked with the project: the Pacific Northwest National Laboratory, the National Renewable Energy Laboratory and the Lawrence Berkeley National Laboratory.
As part of the analysis, researchers examined the importance of standardized metrics, the establishment of evaluation methods and impact assessments for commercial and residential buildings. To achieve results, researchers developed and applied a methodology to assess the value of efficiency for enhancing resilience in new and existing single-family and multifamily apartment buildings in six U.S. cities.
After various tests, researchers concluded the data showed that improving passive efficiency in commercial and residential buildings to meet or exceed current energy code requirements saves lives during extreme temperature events in nearly every situation.
Researchers highlighted energy-efficient strategies that play a vital role in supporting building resilience, including:
- Efficient windows;
- Envelope air tightness; and
- Passive ventilation.
During one phase of the analysis, researchers studied an assisted living facility in Houston, where they explored how resilient the facility was under extreme cold and hot temperatures without power. They then examined how energy-efficiency measures impacted thermal performance.
Researchers selected two extreme temperature events: a six-day heatwave in 2015 and a three-day cold snap in February 2021. During those periods, researchers studied eight passive measures that influenced the building’s passive performance, including:
- Adding insulation to exterior walls and roofs;
- Applying a cool coating to walls and roofs;
- Installing interior window shades;
- Installing solar film on windows;
- Sealing the envelope to reduce air infiltration; and
- Opening windows for natural ventilation when conditions fit.
Over the course of their work, researchers discovered that during a heat wave with power outages, an assisted living facility’s bedrooms failed to meet the LEED Passive House criteria of a seven-day period. While the baseline facility was energy efficient, a lack of natural ventilation and the positioning of windows trapped heat indoors, endangering residents.
For the cold snap, researchers found that bedrooms in the middle of the bottom floor with no or fewer windows maintained higher indoor temperatures due to lower heat loss from the envelope. They also found that window solar film, which improves heat resilience during a heat event, prevented the heat of incoming solar radiation during the day, which could have warmed the facility.
“This negative impact is impaired at night not only because there is no solar radiation but also because the lower U-value of the window solar film helps to trap the heat staying indoors at night,” wrote the researchers. “In addition, other measures that reduce solar heat, including the cool wall and roof coating, benefit the heat event but worsen the cold event.”
Overall, after various analyses of single-family and multifamily structures, researchers concluded that high-performance buildings are safer for occupants and will reduce operating costs while improving air quality and reducing carbon emissions. Alex Wilson, president of the nonprofit Resilient Design Institute and founder of BuildingGreen, recommended that municipalities and states strengthen energy codes and for building owners and developers to establish “more robust specifications for energy and resilience performance.”