Just Curious about Insulation

[babzog]

Pretty sure I know the answer to this, but here goes. My attached double garage is not insulated but was originally sheeted over with OSB on the walls and drywall on the ceiling. I don't believe there's any vapour barrier in there as a result.

If I wanted to insulate, what would be the best way to do this? Blow in insulation from the top of the wall stud cavities (which would mean there'd be no vapour barrier) or rip off the current wall covering, insulate and install VB and new wall covering?

 

[redline9k]

From an architect friend of mine whom I posed the same question, the only real wall you need to VB is the wall adjoining the house as the conditioned air from the house will warm/cool the wall enough to form a moderate amount of condensation.

The other two walls that are exterior (assuming one wall is doors) will see enough airflow and ambient weather that moisture will not be an issue.

This all assumes you do not plan to HVAC the area. If you do plan to heat/cool it more than a day or two at a time, rip it all down and VB the entire thing.

 

[wbrian63]

If you're going to condition the space at all, you'll need some sort of vapor barrier. In cold climates like yours, the barrier needs to be on the inside of the space, in front of any insulation.

There are some "barrier paint" products that can provide some assistance, but I'm not sure of their true performance.

You could probably insulate the cavity, cover the OSB with poly to create a good VB, then drywall over the OSB. I don't know how all the screw holes in the VB would affect performance, but it can't be too much different than VB over the studs with drywall on top. The OSB isn't likely to come off the walls willingly, so you'd probably damage or destroy most of it in the process. Leaving it in place, insulating behind and adding the VB over the OSB is probably the most cost effective and time conservative method, IMO.

You wouldn't need to use 1/2" drywall - if 1/4" is available, that would work just fine since there's solid OSB beneath.

Of course, to make a polished installation, you'd need to tape and float the drywall, and I HATE TO TAPE & FLOAT. That's just me, I'm a perfectionist, and I'm not any good at taping/floating. Low skill + perfectionism = constant irritation...

 

[q20v]

I'm going through this at the moment as well. I live in Ottawa, Canada where the weather varies from 35C to -35C (extremes). I live in an end unit townhouse with both my side walls exposed to the exterior, the ceiling has a bedroom above it and the back wall is attached to the living room. Garage is 20x20.
I bought the house with the garage drywalled, and ended up ripping all the drywall off the side walls, insulating, and putting on a vapour barrier. I'm in the process of re-covering the side walls in OSB. It's been a bit of a pain, but at least I know it's done right. And it should be nice and toasty (relatively) in the winter with a heater.

Good luck with your decision!

 

[grcthird]

If there is any horizontal blocking in the stud cavities, blowing in insulation will not work. Rip it down and do it right. This should yield more time to drink beer whilst making upgrades. Might as well throw in some more outlets and some wires for surround sound speakers, or cable TV? Shoot for a little more work you could even add a coupla windows.

 

[babzog]

If there is any horizontal blocking in the stud cavities, blowing in insulation will not work. Rip it down and do it right. This should yield more time to drink beer whilst making upgrades. Might as well throw in some more outlets and some wires for surround sound speakers, or cable TV? Shoot for a little more work you could even add a coupla windows.

Hehe...

The house is new enough that I'm confident there are no horizontal blocking members in the walls, but yeah, I had kinda figured that ripping it off would be the proper way (and like you said, I can add some mods too). I was hoping that maybe, given that it's not really an airtight space to begin with, that I could safely get away with no VB (thinking of the farmhouses of yesteryear - they were weathertight but not airtight).

I might add a larger compressor at some point down the road as well as an outlet for a welder so I'd thought of running a feed from the main breaker box and adding a garage sub panel. That would allow me to add additional lighting as well.

I don't know if I would add heat to the garage.. working out there in the wintertime is usually less than fun anyway due to the cars melting and the floors being almost constantly wet (don't know if I can do anything about that). No new windows - already have two, plus two man doors and the double garage door.

 

[Need4Speed]

How about drilling a few holes between each stud and above/below any horizontal studs and then fill with expanding foam? Not sure if it would fill all the voids perfectly or if it would create too much pressure and mess something up but seems like it could possibly work.

 

[babzog]

How about drilling a few holes between each stud and above/below any horizontal studs and then fill with expanding foam? Not sure if it would fill all the voids perfectly or if it would create too much pressure and mess something up but seems like it could possibly work.

That would take a couple of Costco sized skids of cans to complete! Re-re will work out better in the long run as I can expand the wiring capability but I also don't want to waste the OSB that's up there now, esp. if the price for same is going through the roof right now. I'd want a way to take it off with a minimum of damage... but every time I've tried to pull the stuff in the past, it's just fallen apart on me.