Should I put foam boards right against my basement wall or leave an air gap?
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Should I put foam boards right against my basement wall or leave an air gap?
Elijah Hargett
Jan. 9, 2021Last updated: Jan. 11, 2021
嗨，我住在印第安纳州西南部，我们家的地下室没有绝缘材料，他们用的是煤渣砌块墙，要么涂了白漆，要么涂了干胶，但我不知道。地下室也是一个步出，所以三面暴露在空气中，而房子的前面是在地下。我的问题是，我是应该在墙里面敷2英寸的泡沫板，还是留一个空隙透气?我知道模具不会在木板上生长，但我担心在一些砌块之间的砂浆上有非常小的裂缝，不知道这是否会影响任何事情。我发现只有一小束光穿过一个街区，我不得不把它封起来。雨水不会直接打在墙上，而且裂缝很小，什么也打不进来。很抱歉我说得这么散漫，但我想给你尽可能多的信息。谢谢你能提供的任何帮助。
There isn’t any need to leave an air gap between the foundation wall and your insulation, in fact it can cause big problems. You’re best to put it right against the wall. See more here on this page –
Why are Basements Moldy? How to Fix & Prevent Mold in Homes
If you leave an air gap then you’re at significant risk of there being an air convection behind the insulation which could increase the risk of mold forming, and also lead to heat loss.
最好把它靠在墙上。但是你提到的光线透进来有点让人担心，墙是什么状况，有很多裂缝吗?它之前是绝缘的吗?这是第一次吗?如果砌块墙一直暴露在外并保持温暖(意味着没有隔热)，那么你就引入了一个新的变量，让它季节性地冻结和解冻。这可能会导致块状基础开裂，因为块状基础比浇筑的混凝土更弱，只靠砂浆粘在一起——这就是为什么光线穿透不是一件好事的原因。
I've went around the house and found only a few joints where there is a "crack". I almost wouldn't even call it a crack because its actually where the mortar is slightly separated from one side of the block like settling. There are no cracks directly through the blocks. The house was built in 1954 and I see no signs of it ever having any sort of insulation in the basement. The conduit for electricity is directly set against the wall with old metal outlet boxes,, no adhesive stuck on the wall, and no holes in the floor of the concrete or up above on the floor joist where there could've been a framed wall. So are you saying I actually need insulation on the exterior to stop the block from freezing and thawing? We have funds at the moment but don't want to pour a ton of money into it. I'm just trying to prevent any further damage to the wall while increasing the efficiency of the basement because we are currently living in it while we renovate upstairs. The furnace kicks on every few minutes and is driving the heating bills up drastically.
Exterior insulation is for sure the best, no question. But it can be a lot more work since you need to excavate. I don't want to instill panic in you about this since tons of block foundations get insulated from the inside and it causes no problem at all, it's just something to consider. Your climate isn't too harsh there so if you think it looks okay then go for it. What can reduce the risk of cracking even more is if you keep it as dry as possible, so make sure water drains away from it not towards it.
What about the condensation that might form between the foamboard and block wall? Won't it eventually just drip down and cause issues with flooring?