Phase Change Material-Enhanced Insulation for Residential Exterior Wall Retrofits
Enhancing conventional low cost blown-in insulation with phase change material (PCM) and aerosealing of the wall cavities
The Regents of the University of California, on behalf of the Davis Campus
Recipient
Davis, CA
Recipient Location
3rd
Senate District
4th
Assembly District
$1,481,114
Amount Spent
Completed
Project Status
Project Result
This project has concluded. Final field results have demonstrated potential reductions in cooling (10 to 41 percent) and heating (-23 to 24 percent) energy, and reduction of peak demand (3 to 81 percent). The wide variance in results was largely attributed to user behavior, primarily due to the removal of a space heater post retrofit (not originally accounted for). The retrofit also enhanced envelope air tightness by up to 58%. Occupants noted improved comfort, reduced HVAC reliance, and decreased noise transmission post-retrofit. Aerosol sealing of envelopes through the attic and crawlspace was effective, fast, and promises to improve indoor air quality and reduce heating energy used in existing homes. As a follow-up to this project, additional funding was obtained to further research on this application of AeroBarrier. CalNEXT is funding continued investigation in the amount of $350,000, and DOE BENEFIT is also providing $760,000 to fund a project for further investigation.
The PCM studied was estimated to increase the R-value of a wall from R-15 to R-18 to R-60 ft2·°F·h/Btu (depending on climate zone). However, it was demonstrated that insulation beyond R-15 ft2·°F·h/Btu has diminishing returns in term of energy savings (approximately 200 to 300 kWh annually), such that it will be difficult to reduce the installed product cost for PCM to sufficiently motivate consumers. The payback period for the entire retrofit ranged from 4.5-41 years, with the fastest payback in interior climates and the slowest payback in coastal climates. Results indicated that PCM may be a lower cost way to achieve high performing envelopes in new construction.
View Final ReportThe Issue
Single family homes built before the 1978 building codes have uninsulated exterior wall cavities that contribute to unwanted thermal losses/gains and air leakage, wasting energy and introducing outdoor air pollutants. This results in excessive natural gas consumption for heating and high utility bills. Existing insulation solutions are either expensive (spray foam) or do not address leakage (blown-in insulation). The cost effective retrofit wall insulation strategies can only achieve limited improvements in thermal comfort and limited reductions in heating natural gas consumption and utility bills.
Project Innovation
This project develops and tests a phase change material (PCM)-enhanced insulation solution for existing homes that have little or no wall insulation, with the goal of showing sufficient cost savings and other benefits to recover the cost within 10 years when compared to existing uninsulated walls. Through modeling and selected laboratory testing, the most cost-effective applications of PCMs for wall retrofit-wall assembly in a range of California climate zones will be identified. This will include analyzing PCMs melting point, amount, and installation location (mixed blown-in insulation or applied to the interior wall surface. The project also tests and evaluates the process for aerosol sealing wall cavities in retrofit applications prior to installing cellulose or fiberglass insulation. Finally, the project will evaluate an optimized PCM-enhanced insulation solution for homes in three climate zones (Bay Area coastal (CZ3), Central Valley (CZ12), and Southern California coastal (CZ9)).
Project Benefits
PCMs are designed to store and release thermal energy at specific temperatures by melting and freezing. Adding PCM has the potential to reduce total heating energy requirements at reasonable cost if designed with the correct melt point, amount, and location in the wall. Aerosealing of wall cavities, prior to blowing in insulation, can greatly reduce wall air leakage and enhance the performance of lower cost cellulose and fiberglass insulation. It is estimated that the PCM-enhanced insulation could reduce emission by 30 million metric tons of CO2eq emissions and reduce criteria pollutant emissions by reducing natural gas and electricity usage for heating and cooling. The cost effectiveness of PCM-enhanced insulation will drive adoption of the retrofit due to improved economic perform
Affordability
It is estimated that the PCM-enhanced insulation could save 5.0 billion therms of natural gas over the next 30 years due to reduce heating loads.This will reduce utility bills for ratepayers while also improving thermal comfort in their home. The timeframe of 30 years for energy saving was determined by the expected durability of the PCM insulation system. PCM is expected to have a lifetime similar to, or longer, than blown-in fiberglass or cellulose ins
Environmental Sustainability
It is estimated that the PCM-enhanced insulation could reduce emission by 30 million metric tons of CO2eq emissions as well as reduce criteria pollutant emissions through reduction in natural gas and electricity usage for heating and cooling over the next 30 years.
Key Project Members
Theresa Pistochini
Subrecipients
TRC Engineers, Inc.
Match Partners
Western Cooling Efficiency Center - UC Davis
Department of Mechanical and Aerospace Engineering - UC Davis
Senseware Inc.
Hearth Labs
