Finishing detached shop

I have a 32x25 detached shop that I’m going to insulate and finish, but I’m really waffling on how to do the walls. Part of the space will be a woodshop, and part for mechanic work. The woodshop will have some heat, at least some of the time, and the amount of insulation for the walls has me going in circles.

The walls are rough-sawn 2x4, 24” oc. I’m thinking of finishing with plywood. I can find R15 unfaced 23” fiberglass. I’m thinking maybe I should add an inch of foam on the inside to slow air movement. But then with plywood over the foam, does that prevent me from hanging cabinets on the wall? The green building sites talk of 50% of the R value as exterior foam. That isn’t going to happen (not going to reside it). ?

 

Is your concern about the rigid foam and cabinets be because of holes from the fasteners going thru the foam? If you put the foam in before the insulation batts, I don't think that would be an issue.

 

I wouldn’t be concerned with hanging cabinets on plywood over foam. Concrete is poured over rigid foam.

It’ll take a lot to f BTUs to warm up a cold concrete slab.

 

Should be no problem to hang cabinets on the wall. Just use ling enough screws to make sure you fasten into the studs. That tiny hole in the foam board won't be noticed.

 

I’m concerned about flex from loading/unloading opening/closing the cabinets being transmitted through the plywood and eventually “softening” the foam insulation between the plywood and studs. Foam before the batts would have to be cut and fit into each stud cavity and would never be as tight as an uncut sheet across the studs. Some people do cut and fit, and then use a can of foam to seal. Looks like a lot of work to me.

 

Yes, the dream on the woodshop side is plywood on 2” foam on the floor. Easier to stand on, and gives the option of conduit under the floor.

 

I was thinking of 1” EPS, or maybe something recycled. I know more is better, but also that the ceiling is more important (2x12, 24” oc).

 

I’ve considered a horizontal board near the top height of the cabinets in place of the foam, but sheet foam the rest of the wall. Then maybe hang the cabinets on cleats, with the wall cleat screwed through plywood, horizontal board, and into stud.

 

Unless you plan on heating the place full time, and to house type temps, just putting standard R13 fiberglass in the walls should be plenty...take your time and make sure the backing is stapled neatly onto the studs before sheeting over it.
Then spend you money on insulating the attic...that and air sealing the space is where the most bang for the buck is.

If you are set on using foam on the walls, then hang the cabinets from over sized cleats...that will spread the load and you'll have no issues...personally, I'd use foil faced polyiso board if it were me doing it this way...

 

The other thing that comes to mind is to use spacers through the plywood and foam insulation...could drill through with the proper size brad point bit, insert spacer (like a piece of 1/8" BIP?) then mark and predrill the cabinets for easy lineup of the holes

 

Thanks - I’ve wondered about the R13 alone - I have no real experience to judge this on. But I do have a few neighbors with heated garages and should be asking them what they have and how they like it.

 

Have you considered using mineral wool batts? Its more dense than fiberglass and air doesn't move through it as easily...also almost fireproof, and the varmits don't like to mess with it! Costs more though...

 

It can be a fair amount of work. I just used caulking (I cannot control the foam sealant and end up with more in places I don't want than in places I do want ). In my case, I only did the bathroom wall and closet wall, so wasn't too bad. I did my basement walls before putting up anything to hang the sheet rock on, so that was easier.

If you put the foam over the studs, the "correct" way is to use a moisture barrier tape (foil or acrylic type) over the seams. That is still a PITA. I used foil in the basement and those rolls never last as long as you think they should. I don't know if using tape would be such a concern in a garage versus a wet-ish basement though.

And, as brenndatomu said, not sure going with more than the batts is worth it for a garage that will be unconditioned a lot of the time. However, if you can ever see yourself making that a living space, then I would go for it from the beginning.

 

No, I hadn’t. Hmmm.

 

It will never be living space, although it might evolve to be a post retirement business space. I’m not terribly concerned about out-bound moisture (no cooking, no showers, no laundry drying), but am concerned about making it tighter to air movement.

 

Will second the mineral wool batts, found way easier to work with once you know how to cut them
And doesn't make me itch like fiberglass!!