haxxer_4chan OP t1_jef7mnb wrote on March 31, 2023 at 4:00 PM

Reply to comment by bassboat1 in Insulating angled roof rafters or laying insulation on the attic floor? by haxxer_4chan

Thank you, out of curiosity, how does that save money if we don't heat the attic (which we do not)? I would have assumed that keeping insulation closer to the floors we do heat would have been more efficient, but I am asking here because I admittedly know very little about it.

bassboat1 t1_jef9lhv wrote on March 31, 2023 at 4:12 PM

You'll be heating less surface area and volume.

In my area (zone 5), ceiling R-value requirement is R-49. The job would require one run of tunnel vents at the eaves, some fiberglass batts to block them up and 18"-20" of blown insulation on the flat ceiling. To get the same R-value on the rafters, you would need either a hybrid of spray foam/batts/rigid board insulation, or build down the rafters for batts. You'd also have to apply R-19 to the gables, and consider a venting solution.

haxxer_4chan OP t1_jefab37 wrote on March 31, 2023 at 4:17 PM

Thank you, this makes a lot of sense. Much appreciated!

shootdang167 t1_jef900u wrote on March 31, 2023 at 4:09 PM

Foam is expensive compared to batts or cellulose

haxxer_4chan OP t1_jef995g wrote on March 31, 2023 at 4:10 PM

Ah right, I totally misread ceiling as meaning rafters and thought they were suggesting the opposite. Makes more sense now.