Garage Insulation Question

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bigboystretchy

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Hello, I have a 2 stall attached garage that I would like to insulate. I would be insulating all the walls and ceiling and installing a mini split for heating and cooling. There will be an attic area above the ceiling, and this is what my question is, this area will be sealed off from the heated/cooled garage, do I need to add a vent of some sort in this area? Thanks!
 

Snoonyb

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There should already be eve vents which will nat be affected by covering the walls and ceiling.
Use 5/8 drywall for both and remember to allow for replacement combustion air, for heating.
 

jcar932

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The surfaces that are insulated should be completely sealed from what's inside. If there is space above the insulation, then yes, there should be some sort of ventilation (from the outside) there.
 

bigboystretchy

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There should already be eve vents which will nat be affected by covering the walls and ceiling.
Use 5/8 drywall for both and remember to allow for replacement combustion air, for heating.
I just checked, there are no eve vents, will putting one vent at the peak be enough?
 

Snoonyb

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Only marginally. Air flows cold to hot, down to up, so any exhausted, will only flow from a replacement source.

We don't know where you are, and have no idea of the structures architecture.
 

kok328

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I just checked, there are no eve vents, will putting one vent at the peak be enough?
You need vents at the soffits and at the peak of the roof. You have to have the correct flow so that it does not flow backwards. A good roofer/builder will be able to tell you (calculate) how much/how many of each (soffit and peak) vents you need.
P.S.- assume your installing drywall over the insulation - per code. Found it is not necessary to install 5/8 board on non-common walls. Are you lapping the edges of the insulation over the stud surface or stapling them into the stud bay?
 

Snoonyb

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The "general" requirement, for attic ventilation Is 1-150, IE, 1sq ft of vent for ea. 150sq ft of attic area, and this is not a geometric calc., so, in a 400sq ft. of garage, the simple calc. is 400divided by 150=3 & 2/3rds, so, install 4sq ft of venting.
 
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