How do you insulate the below grade part of a basement?
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我该如何隔离地下室下面的那一半?
I am about to start a full strip out and rebuild of my basement to make a secondary suite. I've been reading all the information on the site and find it very useful (and educational). I am a carpenter from Scotland living in British Columbia now and as we tend not to have basements at home, I'm finding it a learning curve in building science!
The building is over 100 years old with a half below grade (fully cured!) concrete basement. No exterior insulation, I'm guessing no exterior sealing. But dry dry dry inside.
I like the idea of the 2" XPS with 4" studs and roxul insulation to give around r24 (local code). This is expensive and I'm not 100% on board because the basement is half above grade.
I have seen in the CMHC book a scenario where a vapour barrier starts on the concrete, just above grade height, goes down the concrete wall, under a 6" frame (with R24 roxul batts) and continues up the warm side of the studs (Studs kept off the wall obviously).
Is this a viable solution? Should vents be added to allow full air flow behind the insulation, like in a roof space?
All my knowledge tells me this will be ok but I'm not a scientist.
Thanks in advance!
What part ofBritish Columbia are you located in? BC varies quite a bit in terms of humidity and temperature. I’m just not sure if you think R24 is too much or too little.
We prefer to treatbasement wallsas one singular wall rather than as an above grade and abelow gradeportion.
Granted, there will what some will consider a ‘bit too much’ or a ‘bit too little’insulationdepending on how much you install, given the different temperatures the wall will be exposed to from above grade to below, but those half-and-half solutions pose problems of their own.
有一件事我想说的不是一个好主意，那就是让空气在隔热层后面流动。这可能会起到对流引擎的作用，增加热量损失，也可能导致更多的水分积聚。I don’t quite follow how you describe thevapor barrier那就是在螺柱墙的两边都装上蒸汽屏障，不是吗?
Dry inside does not mean for sure theconcreteis dry, in fact if it has no membrane to protect it from the ground then for sure it is ‘wet’ to a degree. Concrete is porous and will absorb moisture from the ground which will then migrate into the wall, so we like that rigid insulation against the wall to keep the moisture out.
You have probably seen a few of the following pages but I’ll add them in case, and for anyone else reading along.
Preventing mold when you insulate your basement
Building better basements: how to insulate your basement properly
How to Control Radon Gas in Homes