In 2022, the U.S. experienced 18 separate weather and climate disasters costing at least 1 billion dollars, according to the National Centers for Environmental Information. That number puts 2022 into a three-way tie with 2017 and 2011 for the third-highest number of billion-dollar disasters in a calendar year, behind the 22 events in 2020 and the 20 events in 2021. The total cost for 2022’s disasters was $165 billion, with further updates possibly leading to an increased price tag as the final late December storm events are accounted for.
The distress that these climate and weather events inflict can linger long after the event has ended, particularly when power outages get triggered that go on for days or even weeks. Such outages can make life especially miserable for those living and working in buildings that can’t coast and maintain adequate thermal comfort without power. But what about Passive House buildings? How exactly does building or retrofitting to this standard affect occupants during climate disasters?
In part to address this question, the U.S. Department of Energy’s Building Technologies Office commissioned three national labs to come up with a quantitative assessment of how energy-efficiency measures affect building thermal resilience. Last summer the Pacific Northwest National Laboratory (PNNL), National Renewable Energy Laboratory, and Lawrence Berkeley National Laboratory released a report detailing their initial findings from this efficiency-resilience valuation effort. While their findings aren’t shocking, the research contributes significantly to the development of methods for valuing passive building measures that until now were often underappreciated. As noted in the report, policymakers and the building industry need methodologies to support both policy development and investment decisions regarding the reduction of building energy use, resilience, and the overlap between these two factors.
Teams of researchers from each of the three labs, with Ellen Franconi from PNNL taking a leadership role, worked together to develop a methodology to quantify the resilience benefits of building energy efficiency. “We know there is an added value to energy efficiency, so this work was to try to do a better job of how we quantify that,” Franconi notes.
Traditional valuations of energy efficiency have included reduced annual operating energy costs and the associated greenhouse gas emissions. The intention of this study was to more fully and accurately value efficiency by also capturing its effect on diverse aspects of resilience, including habitability, excess mortality, property damage, and investment cost effectiveness. “We came up with metrics that would evaluate over a period of time—seven days—if a building did not have power, how it would perform and how it would affect the occupants and would they be able to shelter in place,” explains Franconi.
The study applied this valuation methodology to existing and new residential buildings for each of six U.S. cities and then compared those results to a building that meets IECC 2021 code and one that meets Phius 2021 standards. The cities—Portland, OR; Los Angeles, CA; Houston, TX; Atlanta, GA; Detroit, MI; and Minneapolis, MN—represent diverse climate types. For each location, the researchers examined and accounted for: 1) the hazard occurrence probability—particularly the combination of an extreme temperature event and a power outage, (2) passive survivability, (3) occupant damage, (4) property damage, (5) operational energy use and emissions, and (6) the associated monetary benefits and costs. The study also included one case study of an assisted living facility in Houston, with an assessment of the impact on habitability and passive survivability of improving the facility’s efficiency.
As an example of the study’s findings, Table ES 1 shows the impact of improving the efficiency of a typical existing single-family building in each of the six cities on standard effective temperature (SET) degree hours, habitability, and excess mortality. SET is a comfort indicator compiled from indoor dry-bulb temperature, relative humidity, mean surface radiant temperature, and air velocity, as well as the activity rate and clothing levels of occupants. Indoor conditions that range from 54°F to 86°F are generally considered comfortable enough to be habitable. Conversely, a cumulative value of SET degrees falling outside the SET thresholds (expressed as SET degree hours) that exceed 216 over a 7-day period indicate uninhabitable conditions.
Projections of the frequency of climate events were based on historical patterns, says Franconi. Historical data tend to undercount the likelihood of experiencing such events, which are increasingly occurring throughout the United States. The impacts of increased building efficiency, with all of the benefits that brings—including habitability—can now be quantified and better valued, thanks to this comprehensive research.
For more information, visit https://www.energycodes.gov/sites/default/files/2023-07/Efficiency_for_Building_Resilience_PNNL-32727_Rev1.pdf