Building America Team: Center for Energy and Environment

Partners: University of California, Davis: Western Cooling Efficiency Center, Building Knowledge, Inc., University of Minnesota Twin Cities: Cold Climate Housing Program, and Aeroseal, LLC

The aerosol envelope-sealing technology developed by the Western Cooling Efficiency Center at the University of California, Davis, uses an automated envelope-sealing method to precisely meet air leakage targets. The process involves pressurizing the building for an hour or two while applying an aerosol sealant “fog” to the building interior. As air escapes the building through leaks in the envelope, the sealant particles are carried to the leaks, where they impact and stick to the edge of the gap, building up and sealing the leaks. A standard blower door is used to facilitate the sealing process and provide real-time feedback and a permanent record of the sealing. The technology is thus capable of simultaneously measuring, locating, and sealing leaks in a building.

This project seeks to optimize the integration of this technology into the construction process by identifying the most appropriate stage to perform the air sealing (e.g., before or after drywall). The project is evaluating several sealing approaches with multiple builders to establish procedures that builders can use to easily integrate the aerosol sealing technique into standard construction practices and reduce the cost of less-effective conventional sealing. This will produce more consistent sealing performance and improved airtightness in a cost-effective manner. The team is conducting the research using the following approach:

• House leak assessment
  • Review existing sealing practices
  • Aerosol sealing demonstration
• Develop two sealing strategies
  • Meet with builder and go over options
  • Pick two promising approaches
• Perform aerosol sealing
  • Seal at least two homes with each approach
  • Evaluate impact relative to baseline
• Refine sealing approach
• Perform aerosol sealing in 3–4 homes using refined approach.

• California homes with sealed attics
  • Open-cell spray foam was used under attic roof deck
    • Sealed before wall insulation either before or after spray foam
    • 78% tighter than target and 39% tighter than control houses
  • Netting and blown-on cellulose insulation used in attic
    • Sealed before wall and attic insulation
    • 49% tighter than target and 48% tighter than control houses
  • 80% average reduction (73%–86%), 1.6 ACH₅₀ at end of construction
  • Used fiberglass/mineral wool in wall cavity
• California homes with vented attics
  • Blown-in insulation in attic
  • Sealed after drywall, mud, and tape
  • Used fiberglass/mineral wool in wall cavity
  • Average leakage was reduced from 6.0 to 1.6 ACH₅₀ (70% average reduction)
  • 66% tighter than 5 ACH₅₀ target

• Minnesota builders
  • Vented attics
  • Closed-cell spray foam at rim joist
  • Interior poly wrap on exterior walls and top floor ceiling
  • Used fiberglass/mineral wool in wall cavity
  • 6 builders and 15 houses
  • 13 homes sealed before drywall
  • 0.75 ACH₅₀ after aerosol (74% average reduction)
  • 6 home sealed below passive house requirement of 0.6 ACH₅₀.

• End of construction air leakage tests for California vented attic houses
• Summary reports
• Builder feedback on aerosol sealing tradeoffs versus conventional sealing
• Develop installation guidelines for various applications
• Energy savings analysis
• Dissemination of final report.

For more information, project presentations, and related publications, visit the Aerosol Envelope Sealing in New Construction webpage.