Air Sealing / Air Barriers

A pre-construction plan analysis  can identify critical  air sealing and air barrier details  and help builder get the biggect impact for the lowest cost and avoid any headaches at the final inspection.

Typical area to be aware of are as follows.


  • Tubs/ shower units on outside walls.

Install insulation and an air barrier on the wall prior to installing the shower unit. Air barrier can be house wrap, or rigid insulation, or spray foam.


  • Basement & attic access 

Door to basement must be weather-stripped

Install air tight door at base of bulkhead stairs

Attic access panel must be insulated and weather-stripped.

Pull Down stair cover

Attic access must be covered with insulated box and be weather-stripped. Options include the Therm-a-dome from EFI 800-876-0660 Product ID# 3570.33


  • Mechanical Chases

Mechanical runs/ chases and penetrations into unconditimechanical chaseoned spaces, attics, and/or kneewalls must be sealed

Caulk all bottom plates of exterior walls kneewalls and garage walls

Caulk all top plates of interior walls to unconditioned attics

Duct Boots must be sealed to subfloor and ceiling board


  • Unfinished slope/eave insulation – Install rigid air barrier on bottom side of insulated rafters beyond kneewall or any other areas where the insulation is not covered by ceiling board. Air barrier can be ceiling board, rigid insulation, and/or spray foam.

 unfinished slopes

  • Knee walls

The backside of all kneewall needs a continuous air barrier installed. Options include wrapping the back of the kneewall with house wrap or installing a code approved rigid insulation board. Note adding one inch of rigid insulation board to a 2×4 wall will be the equivalent of the to meet the new “R-20” code requirement. The ceiling cavity directly below the kneewall needs to be blocked with solid blocks, spray foam and/or rigid insulation board.



  • Overhang /cantilever

Insulate framing cavity to capacity. Seal intersection between overhang and heated space with spray foam or rigid block.



  • Fireplace

Install insulation and an air barrier on the wall prior to installing the firebox.

Air barrier can be, thermo ply, sheetrock or code approved rigid insulation board.


 basement walls

Finished basement walls

  • Install an 11/2” rigid insulation “foundation board” directly to the interior face of the foundation from slab to the bottom of the floor joist using a foam compatible adhesive such as PL 500.
  • Install an ample amount of adhesive around the perimeter of the sheet prior to application to act as an air sealant and gasket.
  • Tape any gaps between the sheets. Foam or caulk any gaps around the perimeter
  • Install stud framed wall against rigid foam board
  • Insulate stud bays to capacity with an unfaced fiberglass or dry spay cellulose




HERS Energy costs top plate leakage





  • Top Plate to attic leakage