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Insulating garage wall(s) and garage ceiling . How to go about it ?

1K views 7 replies 4 participants last post by  iamrfixit  
#1 ·
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Looking to warm up my garage a little, maybe eventually add a heater but I know insulation is step 1. Have 1 exterior wall that’s not insulated or drywalled. Also have pull down steps with storage above. Roof has a ridge vent, no mushroom vents. As far as the ceiling, should i cover the entire “floor” of the attic with plywood, and stick the insulation on that from the bottom or do I have to insulate right against the roof? Now the it’s about 60% plywood, rest is open as you see in photos.
- I’m assuming fiberglass bats would be the way to go but faced or unfaced ?
  • What R value( in WI)?
  • Do i need plastic vapor barrier over everything after?
  • is it necessary to drywall the wall after insulating?

thanks so much for any help
 
#4 ·
Do you park wet or snow covered vehicles in there ? If you, that moisture will go to the cold walls. Not being heated 24/7 means all walls will be cold.
Insulation and drywall from below plus weight of plywood above will max out the load capability of those 2-4’s. IMO
Is that attic isolated from the main house ?
What you describe is a lot of work for little gain. Again, my opinion.
Bud
 
#5 ·
Do you park wet or snow covered vehicles in there ? If you, that moisture will go to the cold walls. Not being heated 24/7 means all walls will be cold.
Insulation and drywall from below plus weight of plywood above will max out the load capability of those 2-4’s. IMO
Is that attic isolated from the main house ?
What you describe is a lot of work for little gain. Again, my opinion.
Bud
Yep wife parks her car in there, usually in winter . And yea that makes sense . That would be heavy especially with drywall. What if I use 1” pink foam ? Stuff’s light. Would that even help ?
 
#6 ·
Those aren't just 2x4's, they're trusses, so your roof is more of a complete system than just rafters and ceiling ties. You still don't want to load a bunch of heavy stuff up there, but your trusses can easily support a full ceiling and insulation. I have insulated and finished every garage I've ever owned, just like this. Even 4" fiberglass stapled between the trusses and a fully enclosed ceiling will make a huge difference in your ability to heat the garage. Of course more ceiling insulation is better, but for a garage that's occasionally heated, even minimal insulation will work. You can use lightweight drywall or even OSB, I've done it both ways.

You'll probably find once the ceiling is fully enclosed that it becomes a real pain to store much of anything up there. That is the price you pay for making the garage space more livable. Having all the walls and ceiling insulated and fully covered makes the space much more temperate, even without constant heat. Interior temps won't fluctuate rapidly and wildly with the outdoor temps. Looks like you have insulated garage doors so that's good. Finishing the space is about a waste of time with un-insulated, thin metal doors.
 
#7 ·
Good to know . Yep garage door is insulated . Luckily I have pull down steps which is what I normally use to get up there or throw stuff up there . So would I need faced or unfaced batts for in between the trusses ? Then plastic over the entire ceiling, then drywall or osb or can I leave the insulation exposed ? What about the wall ? Thank you much
 
#8 ·
I'd use faced insulation just so I had a way to staple it up. Most times I installed the drywall or OSB and went with blown insulation because that's usually cheaper. With blown I always install air ventilation chutes into the soffit in at least every other rafter bay, then tuck fiberglass insulation around those chutes and also into the space at the bottom of the empty rafter bays to keep the blown insulation from going out into the soffit. It's easier as you can just fill the space and don't have to try and keep it from getting out in the soffit.

In a smaller garage, like 24' wide or less, the attic space gets pretty short and very tight. I physically can't crawl around in places like that anymore. Recently finished my son's 24x32 and we left out a row of OSB down the middle. Once the ceiling was up on both sides, we blew the insulation while standing up through the opening on a ladder. Blew in some extra, then as we put the missing piece in place, we raked it around to cover the last piece and level it out.

I've covered fiberglass insulation with vapor barrier to get by temporarily, but I'd highly recommend you go to the extra mile and install drywall or OSB over top to finish the job. It's much more fire resistant and just better in every way to seal it up and stop air movement. If you don't cover the insulation it will always begin to come down over time and develop air leaks that lets your heat escape. I've installed fiberglass both with and without installing additional vapor barrier, not sure it ever made much difference in a garage.