Detached garage insulation question

[fteufert]

I have a 20x20 detached garage, with 10 1/2 foot ceilings. The framing is all 2x6, 14" on center with pull down stairs for an attic. It has Tyvek, OSB, and vinyl siding on the outside, with a 16x7 garage door.

Due to the lack of money, the walls are already covered with OSB. The ceiling has 1/4" fan fold foam board that is covered with OSB. Now I can do it right, but 2 years too late.

My heater will be a vented Toyostove or hot air oil furnace (I can't get a gas line to the garage without dynamite)

The only way to get a vapor barrier is to install it over the OSB, and then drywall over it.

Can I use blown in insulation in the walls and attic floor? The attic has soffit vents and a ridge vent.

I am in Northeast Pennsylvania. It might be -10 this winter or +90.... you never know.

 

[csp]

So the OSB can't be easily removed?

 

[pattenp]

The lack of a vapor barrier is not a make or break issue. Just do the blown in insulation. A good coat of paint can act as a vapor barrier. https://www.gliddenprofessional.com...k/primers-sealers/vapor-barrier-primer-sealer

 

[Scott H in Wheaton]

You can do blown-in for the walls and also for the attic space.

Use a hole saw to drill in between wall studs and fill the cavity til the machine bogs down. Plug the hole and move over 16 inches and repeat.

If you have the funding you could probably find a local insulator to do the walls for you and you can focus on the attic space.

If you would prefer to store things in the attic you could put down rolled batt insulation between the attic floor joists and then plywood over it for a nice floored storage area. Keep the soffit vents clear and free-flowing.

 

[Falcon67]

So the OSB can't be easily removed?

This - one reason I used OSB on my walls. Already had a couple of panels off for other maintenance.

 

[fteufert]

Yes the OSB can come down, but not without a lot of effort moving everything. I like the Glidden paint idea.

 

[matt_i]

I think I'd use a circular saw set on minimum depth to rip a 6" wide strip around the top of the room. Just for ease of patching it back up. Trying to fill holesaw holes is going to be tricky. Screw up a 1x4 as a saw guide.

Make sure you don't cover over the soffit ventilation when spraying fiberglass.

 

[Jlbc212]

I'm with those who suggested taking the osb down, insulating it with fiberglass batts, installing a good vapor barrier and then putting the osb back on.

 

[fteufert]

I just read some articles about blown in insulation. They do not recommend a vapor barrier.

Luckily the top 4 inches of my walls are separate pieces of OSB, since for some reason my builder made the walls 100 inches tall. I will have room to fill the stud cavities.

 

[csp]

Sounds like a good scenario to have when selecting blown in insulation.

At least until the blown in settles over time and leaves the top exposed again.

 

[Jlbc212]

I just read some articles about blown in insulation. They do not recommend a vapor barrier.

Luckily the top 4 inches of my walls are separate pieces of OSB, since for some reason my builder made the walls 100 inches tall. I will have room to fill the stud cavities.

It's simple physics - moisture in the air will condense out of the air at the dew point temperature. On a cold day in a heated garage that temp will often be reached somewhere in the insulation in the wall. Water in the insulation decreases it's insulating ability.

One other point, as a firefighter for many years I witnessed numerous fires involving supposedly "fire retardant" treated cellulose insulation. While the insulation didn't start the fire (that's a story for another day) it was frequently the first material ignited, usually in combination with older "bx" metallic sheathed cable wiring. If you do decide to use blown in insulation, I strongly recommend fiberglass or mineral wool.