Auditor's Field Notes #2: Air Sealing Attics and Basements

The primary source of air leakage is in the place homeowners spend very little time: the basement. Air infiltrates through gaps and cracks in the foundation (and poorly sealed basement windows and doors), travels upward through basement plumbing, HVAC, and electrical chases, and exits through penetrations in the attic. Excessive air leakage into a home can cause cooler indoor temperatures during the winter months and warmer temperatures during summer. So, a home's heating and cooling systems must work harder to keep homeowners comfortable, and the additional fuel required can lead to a one-third increase on annual utility bills.

Recently, I visited a client's very drafty Victorian twin to perform a whole-house energy audit. A blower-door test revealed that the basement, attic roof eaves, attic windows, and skylights required extensive air sealing. Even more, the attic insulation did not meet current code requirements (a minimum of R-38). The basement and attic air sealing were straight-forward. However, the client was concerned that any new insulation would compromise useful storage space in their full-height attic. Fortunately, we crafted a "two for the price of one" solution to insulate the attic and preserve its headroom. 

The attic was already insulated to R-19 with loose-fill fiberglass insulation. To achieve the higher R-value, we installed three layers of 1-inch rigid foamboard insulation on the floor (with an R-value of 6.5 per sheet) and covered it with one layer of half-inch plywood. This saved the clients about 8.5-inches of headroom and gave them a sturdy deck for future foot traffic and heavier items.

Attic insulation that includes proper air sealing can return a homeowner’s investment in four to six years. It's a worthwhile improvement that qualifies for 0.99% financing through the Keystone HELP low-interest energy improvement loan.

Written by BPI-certified Building Analyst Chris Petersen