Vent: I don't buy the idea that thicker batts always mean better insulation

A lot of installers around here just stack up the thickest fiberglass they can find. I've found that proper air sealing does more for heat loss than adding extra inches. In my last few attic jobs, fixing gaps first cut energy use more than doubling the batt depth. It takes more time upfront, but the results speak for themselves.

3 comments

3 Comments

aaronfox1mo ago

Actually, that's a fair point about air sealing being huge, but skipping on batt thickness can backfire in older homes. The math from building science often shows you need both for a full package, especially with our big temperature swings here. Just last winter I saw a house with great sealing but thin attic insulation that still had massive heat loss through the roof. Getting the balance right is what really locks in the savings.

wren1931mo agoMost Upvoted

That example you gave of the house with good air sealing but thin attic insulation is exactly what I'm worried about with my own place. When you saw that heat loss last winter, was it mainly because the insulation itself just wasn't enough to handle the temperature difference? What R-value did they end up needing to add to actually fix the problem, in your experience?

violaa491mo ago

Hey @wren193, did your friend end up adding more insulation too? My friend sealed all the air leaks but still had crazy heat loss because the attic only had like R-19. They bumped it up to R-50 last fall and now their bills are way lower, so I mean it really does make a difference.