How Many Hours-of-Safety Do Our Homes Have in Extreme Weather?

This briefing introduces the concept of "hours-of-safety" to measure how long a home can maintain a comfortable indoor temperature during power outages caused by extreme weather. It argues that improving building envelopes through insulation and air leakage reduction can increase passive survivability and save lives, particularly for vulnerable populations.

• The author defines "hours-of-safety" as the duration a home can maintain the last comfortable temperature it had before internal conditions match the extreme conditions outside during a power outage.
• Extreme weather events are increasing in frequency and magnitude. The National Resource Defense Council (NRDC) estimates that if current carbon dioxide emission levels continue, the United States could see nearly 30,000 heat-related deaths annually by 2100.
• Power outages during extreme weather are a significant risk; between January and June 2019, severe weather caused over 2.9 million customers to lose power for a combined total of 684 hours.
• Passive survivability—the ability of a building to remain livable without electricity, water, or heating fuel—is primarily determined by the home's insulation and the amount of air leakage between the interior and exterior.
• Specific passive design strategies can improve indoor temperatures during outages: white paint on roofs in warm climates can reduce roof temperatures by up to 30°C (86°F) and indoor temperatures by 3.6°F to 9°F. Additionally, lower window-to-wall ratios and natural ventilation are identified as helpful for summer outages.

APA

RMI (2019). How Many Hours-of-Safety Do Our Homes Have in Extreme Weather? https://rmi.org/resources/how-many-hours-of-safety-do-our-homes-have-in-extreme-weather/

Chicago

RMI. How Many Hours-of-Safety Do Our Homes Have in Extreme Weather? 2019. https://rmi.org/resources/how-many-hours-of-safety-do-our-homes-have-in-extreme-weather/.

Wikipedia

{{cite report |author=RMI |title=How Many Hours-of-Safety Do Our Homes Have in Extreme Weather? |date=24 July 2019 |url=https://rmi.org/resources/how-many-hours-of-safety-do-our-homes-have-in-extreme-weather/ |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{rmi2019how, author = {{RMI}}, title = {{How Many Hours-of-Safety Do Our Homes Have in Extreme Weather?}}, institution = {RMI}, year = {2019}, month = jul, url = {https://rmi.org/resources/how-many-hours-of-safety-do-our-homes-have-in-extreme-weather/}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }