Insulation retrofits could save lives in extreme weather: new phase-change materials (PCMs)

Extreme weather is becoming an unfortunate reality because of climate change. The summer of 2023 was the northern hemisphere’s hottest in 2,000 years. Disasters such as heat waves and winter storms impact health and can take lives, and the worst effects are felt by impoverished communities.

In a new study, researchers from the U.S. National Renewable Energy Laboratory outline ways to retrofit residential buildings to make them more resilient to extreme heat and cold. The paper, which appears in Cell Reports Physical Science, focuses on passive routes that do not require energy.

Using a combination of these relatively simple retrofits could increase the length of time the buildings stay safe from 2 hours to 42 hours during a winter storm and from 12 to 37 during a heat wave, the team reports. Besides, these same measures could also make buildings more energy-efficient and help combat climate change.

Climate disasters related to extreme temperatures often interrupt power supply. In the U.S., frigid temperatures in the Midwest during the 2019 polar vortex caused power outages that led to at least 21 deaths. Meanwhile, blistering temperatures above 100°F in the summer of 2020 in many cities led to power outages, water shortages, and many heat-related health issues, including deaths.

Ravi Kishore, Chuck Booten and colleagues at NREL analyzed three promising passive weatherization methods to keep residential buildings safe for the longest period of time. These solutions were: adding extra insulation, enhancing air sealing, and integrating a layer of phase-change materials (PCMs).

PCMs absorb or release large amounts of heat as they transition between liquid and solid states. While they are not used in operational buildings yet, large-scale and field tests have shown a lot of promise for weatherization.

The team used an open-source building simulation tool built by NREL to create a residential building model representing a typical single-family home built in the 2000s in Houston, Texas. They added various combinations of the three retrofit measures to the ceiling, exterior walls, internal walls, and partition walls. Then conducted a whole-building energy simulation under conditions of extreme cold and heat that have been recorded in Texas.

As a performance metric, they measured the time period when the living-zone temperature remains above 15°C during a winter storm and below 33°C during a heatwave. Without any retrofitting, the living zones reach these thresholds in 2 hours for the winter storm and 12 hours during the heatwave.

But adding the retrofit methods to ceilings and walls increased those time periods to 44 hours and 37 hours for extreme cold and heat, respectively. For both winter-storm and heat-wave extreme weather events, the PCM solution provided the most temperature regulation benefits compared to only insulation.

The researchers acknowledge that the study is limited to a single building in Texas and that they only analyzed three weatherizing solutions. In the future, they plan to analyze other retrofit solutions such as radiative coatings, window repair/replacement, and use of natural ventilation. “Finally, some field validation studies along with technoeconomic analysis will be an obvious and important step forward,” they write.

Source: Sajith Wijesuriya et al. Enhancing thermal resilience of US residential homes in hot humid climates during extreme temperature events. Cell Rep. Phys. Sci. 2024.