A timber frame cabin memoir

caver · Nov 24, 2025

The upper back and upper sides are not framed in yet. That rests on the loft floor. You can see that in the video.

caver · Tuesday at 7:24 PM

An insulation guy emailed me a bid after a few weeks. I assumed he had more pressing issues. The prices are approximate, $5900 walls, rim joists and one basement wall. I didn't specify that basement wall so would save a few bucks probably when I talk to him in the near future. This is closed cell 2" spray foam.

For $4300 more it would be a open cell product 5" same areas as discussed before.

If I don't go spray foam the other option would be self install rock wool. I hate fiberglass insulation.

I've only nailed down a few decks boards since winterizing my camper in early November. Staying in a motel is a pain but I can get a clean simple basic room off season for about 60-65$

Carl_NH · Tuesday at 7:41 PM

Does closed cell price include the roof @ 2" too? If so that's a great price then you can add supplement with rockwool.

I really like rockwool the more I work with it but getting the shell sealed up with 2" closed cell is key for structural integrity and eliminating air infiltration.

dstig1 · Tuesday at 8:03 PM

Don't even think of open cell foam. It is vapor permeable and will cause you all sorts of moisture and eventually rot issues. It is only useful in certain situations but is tempting to a lot of people as it is a lot cheaper than closed cell since it expands a ton vs a little for closed cell. So when you say more $ for open cell, I am rather confused...

ponytug · Tuesday at 8:11 PM

@caver We just added some rock (mineral) wool, and I like it a lot better than fiberglass, both in terms of performance and working with it. It isn't nearly as itchy.

It comes in several densities; we used the highest density version to be able to nail it to one wall, and then attached furring strips to allow the second wall surface not to be highly thermal bridged to the first wall.

+1 on using closed cell foam. I'd never use open cell foam for all of the reasons that @dstig1 wrote.

All the best,

Peter

caver · Tuesday at 11:02 PM

Carl_NH said:
Does closed cell price include the roof @ 2" too? If so that's a great price then you can add supplement with rockwool.

I really like rockwool the more I work with it but getting the shell sealed up with 2" closed cell is key for structural integrity and eliminating air infiltration.

Roof is insulated. It is built with what Legacy calls nail base panels. These are R39. I did some research last night and also found that closed cell is the way to go. Unless he made a mistake he quoted the closed cell way cheaper. I'll know more when I talk to him soon.

EddieWalker · Wednesday at 10:40 AM

In my opinion, open cell foam should be illegal in all homes and buildings. The only place it's any good is around window and door frames. From what I've read, it's already been banned in some European countries.

caver · Friday at 7:49 PM

He said the 2" closed cell is about R14 but in his experience it's almost double that due to the tight seal. He has open cell in his home but he said he runs HVAC year round and runs a dehumidifier in the basement. In my situation where I might leave for a month or so the closed cell is how he would go. I told him closed cell is how I would like to go and maybe I can get him scheduled closer to the summer. Like one of you suggested I could always go with a layer of rock wool in front of the spray foam.

dstig1 · Friday at 8:52 PM

For our vaulted great room space, the roof is 14" I-joists spanning from the outer walls to the massive center glulam beam. I did this as a hot roof (cue the outrage...) and as a result had the insulators spray 4" of closed cell foam to meet the standard for avoiding condensing on the roof sheathing for our climate. I then had them staple up netting and do the remainder of the fill in dense packed cellulose insulation. My walls are SIPs so no need there, but it is something you could consider.

The additional benefit your contractor is citing about closed cell foam is the air sealing, which is also critical, but not directly related to insulation R-value. They are related but separate items.

Here is a photo of the ceiling with foam complete and the netting stapled up on one side.