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Joined 3 years ago
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Cake day: July 3rd, 2023

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  • I have done the rim joists in my basement using a similar spray foam product. The biggest recommendations I have are:

    1. Use the kind of gun pictured and not the cans that come with a straw. It is much easier to apply consistently and you can actually stop work and start again the next day using the same can. The straws work OK but they always get clogged when you stop for a bit so only use them if you are working on a small area and plan on using the whole can in one go.

    2. Look into the difference between closed cell and open cell foam. I’ve never seen closed cell come in a can like that so I’d bet money that is open cell foam. It works great for air sealing but you need to apply a ton of it to get an appreciable R-value. Closed cell foam is a lot more expensive in the spray form and is a 2 part mixture that is more complicated to work with.

    What I ended up doing was buying some 2" closed cell foam board at the local hardware store. It’s relatively cheap in board form and is easy to cut. I cut a piece of the foam board to fit inside the rim joist space and then used the spray foam to air seal both the rim joists themselves and the small gap around the foam board. I think this is the most effective way to do it unless you go for the 2 part closed cell spray foam but that was more than triple the cost of the foam board + open cell spray foam.

    For comparison, the 2" foam board has an R-value around 8 and, if memory serves, you would need something like 8" of open cell foam to provide that same level of insulation. You can get an equivalent R-value with 2" of the closed cell spray foam but last I checked the spray stuff was about $800 and an 8’x4’ sheet of 2" foam board is around $60.


  • I don’t have enough space for a horizontal loop so I had to go vertical. The pipes are not PEX exactly but a similar flexible plastic material. Probably 2” diameter. It was pretty expensive but partly because I live in a cold climate. I was already looking at swapping from a gas furnace to an air source heat pump but the heat pumps that function in cold weather are pretty expensive.

    I was going to have to get a new AC unit as well. I also ended up going with a unit that has a desuperheater for hot water. Once you add up costs for a new furnace, AC, and hot water, then subtract the 30% federal tax credit from the cost of the geothermal install it wasn’t as much of a difference as I would have guessed.

    All that to say, our situations are different but if you have space for a horizontal loop and a relatively small house I think you could make it work with a repurposed heat pump and some manual labor. I definitely would have considered that if I had more land to work with.