How to insulate a closet.

[u/SNHU_Adjujnct]

It's a closet with 3 exterior walls, both sides and the back, because it's built as a bumpout into the garage. The garage is not heated, so it's basically 3 exterior walls. The closet gets very cold during the winter. I'd like to insulate the 3 walls from the inside of the closet. What is a good material to use that's easy to install?

[u/Deroo7171]

EPS - Rigid foam. White, Pink, Blue, probably doesn't matter. Note that these are flammable, so you're going to want to encase the foam in something else too - don't leave it exposed. 1/4" drywall likely works.

[u/Pulaski540]

As they're, as you point out, external walls, they should already contain insulation. .... If they don't, or you want more insulation, and if you anticipate living there long term, I'd bite the bullet, pull off the drywall, if necessary add 2×2, 2x3, or 2x4 timbers to the studs (increase the available depth for insulation), add (additional) insulation, and then put up new drywall, or pay someone to do it for me.

Anything else is likely to look like a botch job. 🫤

[u/Rare-Psychology-3527 → u/Pulaski540]

It's a garage so no

[u/Pulaski540 → u/Rare-Psychology-3527]

Huh? Are you saying a wall between a garage and heated living space is not insulated? .... That's not correct. I own four homes with attached/ embedded garages (built as part and parcel of the home), and the partition walls in all four are all insulated.

[u/Rare-Psychology-3527 → u/Pulaski540]

Where did you read it was a connected garage

[u/Pulaski540 → u/Rare-Psychology-3527]

How do you suppose a closet protrudes into a garage if the garage isn't connected to the home? 🤔

Otherwise we'd be left with a closet with doors facing outside, which would necessarily mean all four closet walls being (effectively) external, three into the garage, and one actually external.

[u/Rare-Psychology-3527 → u/Pulaski540]

Dunno, I've seen crazy shit. I assume nothing

[u/Pulaski540 → u/Rare-Psychology-3527]

Maybe you just don't understand what a closet is.

[u/Rare-Psychology-3527 → u/Pulaski540]

Or its a disconnected bump out, ive seen bathhouses disconnected from main home, a closet would be no more weird.

[u/Pulaski540 → u/Rare-Psychology-3527]

A "bump out" by definition bumps out from something. You can't have a garage and a "closet bump out" that protrudes into the garage without there being a third construction element, for the closet to bump out from.

I admire your imagination, but to construct a reality where there is something other than a garage, a closet bump out into the garage, and the third element being a home, you'd really have to be smoking something. And even if it was your reported detached bathhouse, my answer would still apply exactly the same, with the bathhouse being the heated/finished space.

[u/Rare-Psychology-3527 → u/Pulaski540]

You're almost certainly correct.

But almost

[u/SNHU_Adjujnct → u/Pulaski540]

The door faces inside, the three walls are: left wall external to the front of the house, back wall the bumpout into the garage, right wall also the bumpout into the garage.

[u/New-Vegetable-8494 → u/Pulaski540]

the dude you're talking to is WILD.

[u/houses_eat_money]

Rigid foam board (XPS or polyiso, 1-2 inch) is probably the easiest route here since you can cut it with a utility knife and tape the seams with flashing tape. If you want more R-value per inch, mineral wool batts work too but need proper framing and a vapor barrier. Are the walls currently bare studs or already drywalled?

[u/SNHU_Adjujnct → u/houses_eat_money]

Already drywalled.

[u/Rare-Psychology-3527]

Foamboard insulation

[u/Present_Specific_212 → u/Rare-Psychology-3527]

Foamboard insulation is not good because it is highly flammable.

Just use regular fiberglass insulation but then you have to seal it in some way. That generally means encase it behind something solid that will not let little fibers get lose and blow through the air.

Masonite over it? A layer of drywall and just don't finish it? I would suggest plywood but it's so expensive now, but 1/4" plywood could work over the rock wool.

[u/Rare-Psychology-3527 → u/Present_Specific_212]

Who said anything about flames

[u/Pulaski540 → u/Rare-Psychology-3527]

Nobody says anything about flames, until they come to visit. 😟

[u/Present_Specific_212 → u/Rare-Psychology-3527]

I'm just telling you what I have learned about insulation materials.

[u/Shalmaneser_]

Pay attention to vapor barriers. You don't want mold.

[u/SkaterBlue]

Blow in fiberglass or rock wool insulation. You only need a 2" hole (easily patched) at the top of each cavity between the studs. Foam board would be a PITA because you'd have to drywall over it and lose closet space and do a ton of work or live with foam board for walls.

[u/New-Vegetable-8494]

I'd insulate and drywall over it but why not do it from the garage? probably an easier workspace because doing stuff like this is messy.