“Air sealing” refers to sealing the leaks in the building envelope for homes or commercial buildings. Air sealing is generally considered low hanging fruit since the cost to address the leaky areas is usually small and the return on investment is very fast.

Air sealing generally involves sealing off leaky areas with caulk, backer board, expanding foam, insulating gaskets, weatherstripping, and can light covers. If you’re on a budget and your home or building tested as leaky, air sealing (along with lighting improvements) are usually the first improvements to implement. Keeping the heat or air conditioning inside the structure improves comfort level and decreases the load on the HVAC system(s), which in turn reduces costs.

  • Common leaky areas:
  • Exterior doors
  • Windows and/or window trim
  • Bottom of baseboards
  • Subfloor penetrations in structures with basement/crawlspace
  • Penetrations in top floor ceiling such as ceiling fans, alarms, and other electrical penetrations
  • Crown molding
  • Recessed lighting
  • Plumbing penetrations under sinks, behind appliances or bathtubs
  • HVAC registers (gaps around ductboot)
  • Fireplace transitions
  • Fireplace flue vent
  • Attic door
  • Unvented bathroom fans
  • Dryer vents without damper
  • Electrical outlets
  • Kneewall doors
  • Pet doors
Air exchange from wall cavities enters home from gaps around plumbing penetrations
Energy Home Improvements
Cold air entering home from below between wood floor boards
Cold attic air entering home through unvented bathroom fan
Hot attic air infiltrating home from around unsealed can lights
Cold air entering home from unfinished basement through gaps around leaky floor register
Cold air entering home from under double doors
Cold attic air infiltrating living space from around periphery of drop-down attic stairway
Whole house fan fins allowing 106 degree heat into home