Timeline for Do I need to leave space between insulation and the roof deck with a cathedral ceiling?
Current License: CC BY-SA 4.0
17 events
| when toggle format | what | by | license | comment | |
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| Apr 18, 2021 at 19:15 | comment | added | A_P | Update: the only material available at any nearby Lowe's or HD is R-30 rockwool at 7.25". So I'll use that with an inch above and call it good I think! | |
| Apr 18, 2021 at 18:10 | comment | added | A_P | @ThreePhaseEel Ah. Shingles (presumably asphalt). | |
| Apr 18, 2021 at 18:08 | comment | added | ThreePhaseEel | @A_P -- that OSB is the roof decking, sorry about my terminology, I meant the roof cladding | |
| Apr 18, 2021 at 18:05 | comment | added | A_P | @KH Or maybe just use 5.5" R-21 and add furring(?) to the rafters to give that extra inch for breathing. Kinda leaning that way right now. | |
| Apr 18, 2021 at 17:51 | comment | added | A_P | @ThreePhaseEel Good question! I've updated the post to show an image. Appears to be OSB :( | |
| Apr 18, 2021 at 17:51 | comment | added | A_P | @KH I think Austin qualifies as "particularly hot." I've found 8.25" fiberglass and 7.25" rock wool at R-30 (but it's more expensive). So for fiberglass it sounds like I'd have to add at least (8.25-5.5+1) = 3.75" of spacing to make this work well? BTW I'm having my drywall guys do it. I suppose they probably know how to add furring or whatever? | |
| Apr 18, 2021 at 17:46 | history | edited | A_P | CC BY-SA 4.0 |
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| Apr 18, 2021 at 17:40 | history | edited | A_P | CC BY-SA 4.0 |
added 30 characters in body
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| Apr 18, 2021 at 16:57 | comment | added | ThreePhaseEel | What material are you planning to use for the roof sheathing? Asphalt shingles? Metal roofing of some sort? Something else? | |
| Apr 18, 2021 at 3:59 | comment | added | K H | If you are in a particularly hot climate the air gap and extra insulation may be necessary as well, especially if you intend to cool the place. | |
| Apr 18, 2021 at 3:55 | answer | added | P2000 | timeline score: 1 | |
| Apr 18, 2021 at 1:08 | comment | added | crip659 | Probably not. That inch of air would probably reduce the temperature on top of insulation by quite a few degrees, reducing the need for extra R value and maybe a few extra years of life for the roof. Could also nail 2x2s, or 2x3s to rafters to give more space, imagine a couple of inches will not cause headaches. | |
| Apr 18, 2021 at 0:56 | comment | added | A_P | The crux of my question is whether that inch of air is even necessary. Right now I'm thinking it's not. | |
| Apr 17, 2021 at 23:36 | comment | added | crip659 | If you use white paint, that will probably be more helpful than an extra R 7. Just need about an inch of air, so maybe just foam or a mixture. | |
| Apr 17, 2021 at 23:05 | comment | added | A_P | Hmm it might help the roof longevity, but at the cost of heating up the interior, which is not what I want. Better to put elastomeric paint over the shingles if that's what I'm trying to solve. | |
| Apr 17, 2021 at 22:50 | comment | added | crip659 | A bit of air would help in cooling down the roof deck. Austin TX, hot hot sun beating down, bet you could fry an egg on roof. Think what that would do to asphalt shingles. | |
| Apr 17, 2021 at 22:20 | history | asked | A_P | CC BY-SA 4.0 |