Budget-Friendly Garage Roof Insulation
I have a garage here in climate zone 4a. I have a 3 pitch roof that runs into a wall at the top. The roof is a mono truss 2×4 on 24″ centers topped with OSB, ice and water shield over the entire roof with architectural shingles. I was talked out of a wall to roof vent by my roofer. With the location of the vent and such a low slope roof, he said it was bound to leak in wind driven rain and snow. Which I agreed with him that the chances were very likely. So, now that brings me to how to insulate the roof with no venting. The roof is new, so that takes away any type of topside insulation. Plus, there are many details that would have made that extremely difficult in the first place. I talked to a spray foam contractor who said he would only put 3″ of closed cell foam on the underside of the roof deck and that would be sufficient with no other insulation needed. I don’t agree with that, but the cost of adding more spray foam insulation to an area 24×52 is substantial. The cost of this project is already way over budget due to all the added costs from COVID-19. I’m looking for something as budget friendly as possible.
Thanks
Colby
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Replies
Tell us about your plans for conditioning the space (or not), your goals in insulating it (lots of good reasons to do it--just wanting to know prioritities) and what is on the other 5 sides--are they outside walls or attached to a house, and are they insulated, and what about the floor?
One more question: how much headroom do you have and would you mind losing some below the low end of the roof?
The first floor is roughly 2500sqft and 1000 sqft of 2nd floor. Not all of the 1st floor has a 2nd story over it. 23x52 is a high bay with a 15ft ceiling with no 2nd floor over it which is the roof that doesn't have a good way to vent. I plan on heating the entire garage throughout the winter, and will eventually put AC in. The floor is a 6" slab with radiant heat in it. The garage has 3 sides exposed to the outside and the other is a common wall with the house. The walls are not insulated yet, I haven't decided if I'm going to go with fiberglass batts or blown in insulation yet. The walls are 2x6. I don't think there is any reason to lose headroom as the roof is made from trusses and not rafters.
Thanks
Colby
With trusses I would sugest just finishing the ceiling on the bottom of the bottom cord of the truss. I would sugest a vapor barrier and a material of your choice. Drywall or corrugated steel and then do blown in insulation. For venting I would go with powered vents on the gable ends or
Intake vents low on the gables and powered vents near the ridge.