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Community and Q&A

Balloon Frame Basement Air Sealing and Insulation

hustle | Posted in Green Building Techniques on


I have a 1906 balloon-frame house in Essex County, NJ (Zone 4A, borders 5A). My unfinished basement is quite cold, which makes first floor cold as well.

The foundation is brick (below grade) and rusticated cinder block (above grade). The 2×4 (true) studs rest on a 6″ wide x 3-3/4″ high sill. The ends of the 9-1/2″ floor joists are notched so that they rest on the sill, with their bottoms even with the bottom of the sill. There is no sub-floor; the floor boards run past (or are partially notched around, depending on the direction) the studs. There is thin blocking installed between the studs, on top of the floor boards, which closes up (but does not seal) the bottom of the stud bays. Sheathing is tongue-and-groove, run diagonally; siding is wood claps on the first floor, wood shingles above.

There is no insulation in the house. The attic (third floor) is partially finished; renovating it (and insulating) is a later project, as is insulating the wall cavities.

I’m trying to put together a plan of attack for air sealing and insulating the basement. How does the below look, in terms of sequencing (i.e. most bang for the buck first):
– Air-seal (using caulk and canned foam) between foundation and sill, and around window frames.
– Install storms on basement hopper windows. I want to keep the original windows.
– Replace original exterior door, which leads to steps and a Bilco-type hatch.
– Insulate (using rigid polyiso, sealed with canned foam) from the top of foundation to underside of floor, between the joists. What would this detail look like? Do I need to install horizontal insulation at the bottom of the stud bays or will vertical insulation from sill to floor and/or from foundation to floor suffice? What R-value should I be shooting for?

I would much prefer to tackle the insulation myself, bit by bit, which is why I’m proposing cut-and-cobble instead of spray.

Am I missing anything? Thanks very much.


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  1. GBA Editor
    Martin Holladay | | #1

    It sounds like your plan makes sense. In case you aren't clear on the issue, you should know that it's important to insulate all of your basement wall, from the footing on up -- not just the rim joist area.

    Here are links to three articles that will guide you in your work:

    Air-Sealing a Basement

    Insulating rim joists

    How to Insulate a Basement Wall

    -- Martin Holladay

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