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Community and Q&A

Prepping the rim joist for spray foam in cold weather

svquv9Qkge | Posted in Energy Efficiency and Durability on

I live in upstate NY (climate zone 5 or 6; I’m right on the line) in a brick house that was built in 1850. My foundation walls are at least 14-in. thick stone (with mortar joints). I believe the house is balloon framed, but I haven’t lived in it long enough to figure that out yet. I’ve heard from the previous owners that there’s blown cellulose between the walls and the brick. There’s some evidence on the exterior that this might be true.

I’m in the process of air sealing what I can, mainly in the basement right now. (the storms are in excellent shape, and the house is otherwise pretty tight for its age). After the basement I’ll venture into the attic to air seal up there. (There’s about 10-in of cellulose in the attic; I’ll add more if/when I can). I purchased a spray foam kit (the FrothPak) and plan to hit the areas of the rim joist that are accessible soon. Some of the bays are filled completely to the subfloor with stone, but in many others the stone has been carved out to make room for pipe and wires. So those are the areas that I’m going to focus on most.

I know the middle of winter isn’t the best time to be doing this work. I hit both the stone and the rim joist with an infrared temperature gun and get readings ranging from 35 degrees up to 50 (most in the 30s and 40s). Does anyone have any tips on how to raise the surface temps w/in the bays that I want to spray? (Rigid insulation isn’t an option here b/c of piping and the depth of the foundation walls – I can only access these areas with a spray gun). Any tips and insights would be greatly appreciated.


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  1. GBA Editor
    Martin Holladay | | #1

    The usual way to raise the temperature of a basement (and the interior surface of the foundation) is with a heater. Your options include: the home's furnace or boiler; one or more electric space heaters; a Torpedo heater that burns kerosene; or a radiant propane heater (like the ones used in ice fishing shanties).

    If you want to direct the heat to a small area, you can use a hair dryer.

  2. svquv9Qkge | | #2

    Thanks, Martin. I must not have worded my question very clearly. I was looking for some advice on ways to direct heat the surface temp since heating the entirety of the stone walled foundation in this climate in the middle of winter seems a little crazy. It's unfinished basement so using the boiler isn't an option. I wondered about Torpedo heaters but it's a large basement and I didn't know how long it would take to raise the surface temp with that method. It seems your final suggestion of the hair dryer is a good one - I never thought of it, though now remember Dan Morrison mentioning that he'd used this approach in his house. At least I think he did. Anyway, thanks.

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