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Old 04-11-2013, 01:17 PM   #1
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Re-Insulating 1960's Attic - Vapor Barrier, and General Input Requested


Hi DIYC,

I'll try to keep this short.

Attic1: Two gable vents on the east, one on the west with a new attic fan (set to 95F). Roof is old, has two layers of shingles, no soffits, no stack vent (I think it's called). No appliances in the attic, no ductwork. Just some plumbing vents pipes, one ceiling light (not recessed), and one bathroom fan/vent not vented properly (dumps into attic, will fix with roof vent).

Existing Insulation: Combination of the yellow stuff with poorly done paper backers facing the conditioned space (correct, but incredibly weak/old), perhaps another layer with paper backing also weak, and facing into the attic, which is wrong), and then some pink non faced just kind of thrown about, and some mineral fiber wool stuffed along the walls into some drops.

So far...I've pulled up what was there, found a junction box, the ceiling light, bathroom fan.

My wife is in love with the idea of spray foam. She'd vote for 2 feet of it if she could. Anyway, she'd like to do 2 inches of spray foam, and then blown in celluose over that.

I've been doing a lot of reading. I'm thinking if putting in 6mil plastic between each stud (stapled into the studs, touching them, touching the sheet rock underneath, and then to the other side), as a vapor barrier. Other people/things say I don't need vapor barrier, the paint/sheetrock already does that.

I was also thinking of air-sealing via GreatStuff foam, any places that look like they need it. Then lastly, spraying in R60 worth of cellulose. I plan on removing all of the existing insulation. (Might be overkill, it does not appear rodent or mold invested).

Concerns - When the roof gets redone ~5yrs, do they make a mess and dirty up the nice new insulation? Does it not matter because the airflow from the gable vents will taint/dirty the insulation in due time anyway? Should I even both with a 6mil plastic vapor barrier, then do the cellulose blown in (think Lowes, or AtticCat,etc)?

Attic is not used for storage, and I will install a proper hatch [http://www.essnrg.com/] etc.

I guess that's enough for now! Thank you for your input.


Last edited by phoenix_iii; 04-11-2013 at 01:25 PM.
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Old 04-11-2013, 01:39 PM   #2
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Re-Insulating 1960's Attic - Vapor Barrier, and General Input Requested


Foam, in the case of a traditional vented attic that is accessible, is huge waste of money if you use it for anything but air sealing (speaking about the floor layer).

Spot seal with foam and/or caulk all the top plates, penetrations, etc.

Open up the soffits if you can and install a ridge vent when do the roof.

R-60 cellulose is probably overkill but if you are doing it, its is pretty cheap. R-50 is E-Star and sufficient.

Be sure to use a borate only stabilized cellulose.

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Old 04-11-2013, 06:39 PM   #3
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Re-Insulating 1960's Attic - Vapor Barrier, and General Input Requested


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Originally Posted by Windows on Wash View Post
Foam, in the case of a traditional vented attic that is accessible, is huge waste of money if you use it for anything but air sealing (speaking about the floor layer).

Spot seal with foam and/or caulk all the top plates, penetrations, etc.

Open up the soffits if you can and install a ridge vent when do the roof.

R-60 cellulose is probably overkill but if you are doing it, its is pretty cheap. R-50 is E-Star and sufficient.

Be sure to use a borate only stabilized cellulose.

Yes. Looking for foam for AIR SEALING ONLY. Was thinking though, can't I use a combination of Great Stuff + rigid foam to achieve the same thing for less coin (DIY, if I spray foam, I'll hire it out).

I do not have soffits in this roof, I was told some would be installed when the roof is redone.

What do you think?
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Old 04-11-2013, 09:22 PM   #4
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Re-Insulating 1960's Attic - Vapor Barrier, and General Input Requested


Got a picture of the roof and the soffit area?
I've neven once seen a roofer add soffit vents.
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Old 04-15-2013, 12:18 PM   #5
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Re-Insulating 1960's Attic - Vapor Barrier, and General Input Requested


No picture handy. When I go up there and pull all the insulation out I can show that there are no soffits. I was told that by the home inspector (I think) that when the roof is redone they can add soffits.

It has 2x gable vents on one side and 1x on the other (where I put the fan), so I think ventilation is adequate. It's small, maybe 900sqft.

I keep getting told I don't need to airseal (either with plastic, or a full layer of 1'' foam).

I think I am going to use GreatStuf in a can to seal the sheetrock to joists, any place air could slip in, and then just blow cellulose over that. So basically a ghetto air seal to prevent 'air washing'... Thoughts?
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