Which insulation for my shop?

Hey guys. We recently got a new house, which as a bonus came with a fairly nice 24x30 metal shop, I'm wanting to get it insulated, and I've got a couple quotes for closed cell spray insulation, roughly $4800 bucks. That's a little too steep for me. My neighbor has an old guy who does alot of work for them, and just insulted their small metal building they got. He used what looked to be 2in thick sheets of Styrofoam to insulate it, he put small strips behind the sheets of foam to let the building breathe. He's been building houses for 40yrs, so I'm sure he knows what he's talking about.

My only issue with the foam sheets is flammability. I do alot of metal work, and I don't want the stuff to catch fire (it would be covered eventually, probably by plywood, but not immediately). The shop won't be cooled, but I will have a wood burning stove to keep it warm in the winter.

Any suggestions for any kind of insulation are welcome.

 

Do you have Roxul rock wool batt insulation available in your area? It’s sound deadening, will not burn, and much nicer to work with than fiberglass batts. It’s what my stud-framed shop is insulated with, and a poly vapour barrier on the inside.

 

Following. I have a metal shop too and primarily do metal working also and have been lazily looking for insulation, but if I can even find anything it's like $10k and a pain in the ass--so I just suffer

 

I would do the math...styrofoam isn't cheap either. The price difference may not be as much as you think.

 

Im very happy with my sprayed in foam stuff. Cool in the summer, warm in the winter. Been trouble free for 6 years now, but i also paneled with 4x8 osb. Its turned a darker yellow over time, and i dont have birds nesting in the rafters, but i see scorpions up there every now and then.

had em fill the center, since i could cut it out if i needed more flow for the ridge vent, but i havent had to yet.

 

You don’t need venting with spray foam. Closed cell is an air barrier and moisture retarder. Should not be left exposed in this application. Could be painted over with an intumescent thermal barrier paint or more preferably drywall or plywood.

diy kits are generally more expensive for the materials than I charge to come and supply and install it professionally. They are finicky and is this really something you want to do yourself!

Used to be about $0.90 per square foot per inch of thickness materials and labor. Figure more like $1.35 now. So a wall 24’ long and 10’ high with no doors or windows is 240 square feet. $324 per inch of thickness applied. R value is about 7 per inch. Typical install 2-3” in a wall. 3-5” in a roof/ceiling.

 

Mineral or “rock” wool. It has good insulating capability, and it’s hydrophobic, sound-deadening and non-combustible. Now available in most big box hardware stores, mineral wool or rock wool is readily available and fairly reasonably priced. It is an excellent insulation choice.

 

Wow, I woke up to a ton of replies! I appreciate the feedback and will be keeping everyone updated on my progress.

 

Hmm interesting. That seems like a better rate than what I was quoted. One guys said $4760 for 1.5in closed cell walls and roof deck.

 

It's heavy af but works great. It's way overkill for my shop, just gotta make sure to not stand in front of it when turning it on or you get pelted with all kind of floor debris

 

We were told we couldn't use spray foam due to the moisture retention. Didn't jive with the way our crawl space is ventilated. The guy said new houses are designed with spray foam in mind. Ours was built in '83. We put radiant barrier up there instead.

 

I should be a little more specific. I generalize but then I forget my audience.

With spray foam you do not need the traditional venting such as soffits, rafter vents, ridge vents and gable vents. The purpose of this venting is to wash away the warm moist air so that condensation issues do not occur.

however you must have provisions for ventilation inside the home…air exchange erv etc. because the house will be so tight you must mechanically exchange the air to allow fresh air and maintain proper humidity levels.

Same word, two completely different aspects of building science.

 

Another vote for rock wool insulation. Used it when I put a meat locker in my shop a couple years ago. Works great and very easy to work with.

 

Yeah he mentioned that too. Basically vacuum seals the place but the house has to breathe right lol

 

So I've been researching rockwool. Didn't know anything about it beforehand, but it looks like some pretty amazing stuff! My total area to insulate is around 1630 sq ft, that's the walls and the roof. The metal poles are spaced 5ft apart, and the rockwool is made for 16in centered studs. Should I frame it out with 2x4s to fit or just stuff is together nice and tight between the 5ft gap? Maybe put some kind of tape between pieces of insulation? I'd rather not buy a bunch of overpriced lumber if I can help it.

And vapor barrier. Do I need it? Do I install it before the insulation goes on, or afterwards?

All the gaps from the ridges in the metal siding and roof, do I leave that open to breath or do I take a can of great stuff foam and seal it up? I might be installing 2 small vents on either side of the shop if airflow matters. I'd really like to seal it up if possible. I'm also gonna run 2x4s across the ceiling to hold the insulation in place and give me something to mount the osb to. Might need to beef up the existing trusses first to handle all the extra weight. They're kinda wimpy.

My shop is a complete wreck right now. So don't mind the mess. It's all gonna come together soon. Once insulated and walled in I can actually organize and build shelves.