Had a professional attic air sealing job done on our 1978 Scarborough home as the first step in our energy upgrade program. Posting the blower door results before and after to help others quantify the benefit.
Why We Started With Air Sealing
Our EnerGuide evaluation (done in fall 2024) came back with:
- EnerGuide rating: 61
- ACH50 (air leakage): 7.8 air changes per hour
- Attic insulation: R-14 (well below current R-60 target)
- Advisor’s recommendation: air seal first, then top up insulation
What Was Found in the Attic
Energy advisor and contractor did a joint attic assessment:
- 14 pot light housings penetrating the ceiling (none AT-rated, all leaking significantly)
- 3 plumbing stacks unsealed where they penetrated top plates
- 2 bath exhaust fans ducted into the attic (not outside) - corrected
- Top plates at all interior walls showing heat streaking in thermal camera
- Attic hatch: bare plywood, no insulation, no weatherstripping
Air Sealing Work Done
- Replaced all 14 pot light housings with ICAT-rated airtight LED fixtures from above
- Foam sealed all plumbing stack penetrations with Great Stuff Pro
- Re-ducted 2 bath exhaust fans to exterior (roof cap)
- Sealed all top plates with acoustic sealant
- Installed insulated attic hatch cover (R-40 rigid foam box)
- Sealed around all partition walls
Cost: $2,900 (no insulation added in this phase)
Post Air Sealing Blower Door Test
Before: 7.8 ACH50
After: 4.9 ACH50
A 37% reduction in air leakage from sealing alone.
Energy Impact (First Heating Season)
Gas bill Oct-April 2025-26 vs prior year: $1,890 vs $2,340 = $450 savings.
Next step: add blown cellulose to bring attic from R-14 to R-60. Quote received: $3,100. Combined projected annual savings: approximately $750-$900/year.