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Basement rim joist insulation

Posted: Sun Mar 10, 2019 4:39 pm
by Dstruktion
Hi guys,
Thanks a lot for all the videos. Quick question about insulation in my basement. I live in Winnipeg, Manitoba, Canada. (Read:cold) My basement has insulated walls with vapour barrier but the rim joists are not insulated. I was going to follow your instructions in the videos as to how to complete this but one question;how do you marry up the top of the vapour barrier that’s existing in the walls to the new insulation I’ll be putting in the rim joist? I was thinking if I use foam in the rim joist, I would have to just spray it so that it covers the top of the vapour barrier. If I use rigid in the rim joists, I would just have to either use acoustic or tape to seal the vapour barrier to the rigid. Your thoughts? It’d be much appreciated. Thanks again for all the help you’ve already given.
D

Re: Basement rim joist insulation

Posted: Sun Mar 10, 2019 7:02 pm
by Shannon
So if you use spray foam spray the cavity and continue to spray the bottom of cavity until you seal to the top of the top plate of the wall. Spraying to the poly will do nothing as the foam does not seal to poly well at all.

If using rigid foam I would recommend a slightly different approach than my video. Install rigid foam against the outer rim vertically and then fit another piece horizontally from that vertical piece out and onto the top plate of the wall. All seams would then get sealed with canned spray foam. Add additional layers of Roxul insulation over the foam pieces to cover them up a protect from exposure to fire.

Re: Basement rim joist insulation

Posted: Sun Mar 10, 2019 8:15 pm
by Dstruktion
Ok I get it. But how do I affix the horizontal piece of rigid to the top plate?

Re: Basement rim joist insulation

Posted: Sun Mar 10, 2019 9:55 pm
by Shannon
The spray foam will seal it into place.

Actually it will be easier if you install the horizontal piece first and vertical over it. This way you can see the joint between the two and it is easier to foam.

Re: Basement rim joist insulation

Posted: Wed Mar 20, 2019 11:14 pm
by MindBender
What is the purpose of horizontal rigid foam?

I used regular fiber insulation and vapor barrier sealed all round with staples and tuck tape.

Always looking for better way.

Re: Basement rim joist insulation

Posted: Thu Mar 21, 2019 9:07 am
by Shannon
Well first off Tuck tape does not stay sealed well against wood in the long run you get areas that release and leak air. Second if you have ever tried to do this with acoustical instead you end up a very tedious job and usually acoustical on you ,your clothes, and tools. :D :o
With foam you can cut it pretty quick to fit close and seal it in with canned spray foam very quickly, generally with out much fuss and mess.Usually 2" foam done this way eliminates needing poly vapour barrier.