Insulating first floor cantilever…
I have about 40′ of the front of my house where the first floor cantilevers about 14″ on top of the basement crib walls.
I’ve opened up one end from the inside for some renovation, and found that there is no insulation in the space between the basement wall and the rim joist. I can put 11″ of fiberglass in the space in the part I have open, but the only way I could do the rest is to come in from underneath (probably with foam).
Is this likely to be worth is from an insulation perspective? The walls are R-11, the windows are okay (but will be soon upgraded), and the attic has about R-30 in it.
Replies
I had an open cantilevered floor insulated when living in Washington, the energy experts recommended fiberglass batts and enclosing the bottom with tyvek. Worked fine, but that was over 20 years ago - didn't have foam then.
, but the only way I could do the rest is to come in from underneath (probably with foam).
You answered your own question. Foam is the way to go, either sprayed in or cut and fit a layer of 2" rigid panels with spray foam sealing the joints. Fiberglass is almost useless in those areas,BTDT.
Comfort level in the basement will go up considerably when you stop air from moving through those drafty areas, and the first floor will benefit too.