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The insulation math that blew my mind on a job in Denver last month
I was adding up R-values for a garage conversion and realized a 2 inch gap in the air seal drops performance by like 40%. Found that stat on a Building Science Corporation blog and double checked it because I didn't believe it. Has anyone else had their whole insulation plan wrecked by one tiny leak?
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grace_knight701mo agoMost Upvoted
Wait, like a 40% drop from just a 2 inch gap? That can't be right. I've been in attics where there's a whole foot of missing insulation and I thought that was bad, but two inches? That's just a crack you could fill with a can of spray foam. Makes me wonder how many houses I've worked on where I missed a tiny gap like that and ruined the whole job without even knowing it. Now I'm gonna be paranoid about every little seam and corner.
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the_margaret1mo ago
Right, but the real killer is that gap lets warm air hit the cold surface and you get condensation inside the wall. Rot and mold before you even know it, not just a cold room.
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Close, but it's actually the air seal gap versus the total R-value that changes the math.
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