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Batt insulation in attic rafters without drywall?

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I’m in zone 3 using rockwool batts

As long as my roof is vented between my rafters can I insulate between them in my attic without covering it with drywall?

I have a small space in my roof that I’m not heating but I want the roof to be insulated, I won’t be able to drywall there because of ductwork

Is ok to have insulation in this space with no drywall?
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Discussion Starter · #3 ·
Bring your insulation to the knee wall and allow the rafter to breathe. I trust you do have soffit venting as well as a ridge vent. Baffles are needed along the run to allow air to pass over your insulation and out to the atmosphere.
The roof has a 1.5 inch vent all the way to the top, and I’ve put insulation in the whole roof, just didn’t know if that small space at the bottom behind the wall would need drywall on it or not, it’s an unheated space. I’ll have 2 small access doors to the area though for maintenance
 

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Discussion Starter · #5 · (Edited)
I wouldn't expect a problem with that.
Moisture was main concern, I wasn’t sure how it would work in this situation since that part of the roof will have no air seal with drywall

how is it normally done in attic spaces if someone wants to insulate the roof in a traditional house using batts, do they put drywall on their attic ceiling?
 

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Discussion Starter · #7 ·
Normally you have conditioned air on the inside to worry about, so unless you are heating the space you are just storing some batts in that space. The drywall on the inside is about keeping moist house air out of the insulation. If it is a closed space there is no house air in there.
Ok thanks, I will have a couple of access doors though that will be opened from time to time, but hopefully they won’t have any major air leak while closed

but the roof is vented there anyway so maybe that wouldn’t be a problem anyway, i guess they would be no different than pull-down attic ladders
 

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Discussion Starter · #10 ·
I didn't see where you answered the question asking about soffit vents or other low vents. Without a source of incoming air there will be no ventilation and that can result in moisture build up.

Bud
Yes there’s soffit vents at the bottom of the roof

vent at the top vent at the bottom

1 inch - 1.5 inch space behind the insulation
 

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Discussion Starter · #11 · (Edited)
There are 2 or 3 spots in my roof where my second floor joists blocks a few inches of the width of my vent though, I opened it as much as I could without damaging my floor joists

those few spots are probably only half as open as the rest of the vents, there’s not really anymore I can do about those though
 

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Discussion Starter · #12 ·
I am going to have some outlets on that wall, I’m going to seal them the best I can but I suspect some air is still going get through them into that unheated space with no drywall

would that be problem or no since my whole roof is vented
 

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Discussion Starter · #14 ·
If you still have access to the back of the receptacles, spray foam around the perimeter of the box to help keep air infiltration to a minimum.
Ok, I’m also in zone 3 if that makes a difference, like I don’t know if air sealing is as critical for zone 3 for moisture

isn’t spray foam flammable?
 

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Discussion Starter · #16 ·
Air sealing between atmospheres is critical. You have a conditioned side and an unconditioned side.

Spray foam is flammable as it comes out of the tube, and will smolder if direct flame is applied. The small amounts you will be using will be negligible for fire, but will help immensely with air flow.
I know it’s important I’m just guessing it would’ve be AS important as say if I was in zone 5 or 6 right?
 

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Discussion Starter · #18 ·
Conditioned and unconditioned air will migrate no matter what your zone is. I'm not sure of your temperature extremes, but I'd say you are rather warm. I'd like to keep my air conditioning in the living space.
Yes I want to keep the cool air in, I meant more for moisture getting in my roof compared to zone 5 and 6
 
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