Best insulation for shop?

My shop is already built, but I didn't insulate at the time I built it. But now I think I want to so what is the best way to do so if the skin is already hung? Does anyone have any experience with the spray-on expanding foam insulation. I hear a lot of people talk about it, but I have never seen it, nor do I know who provides this service. Anyone in the Atlanta area know about this?

Anyway, I am up for ideas.

Thanks!

-Les

Atlanta? Trying to keep the AC cool?

The garage I work in is "lightly insulated" with spray foam, but it uses a cement floor. The floor stays cold regardless of time of year. I know a guy that poured the cement in his garage to accomodate cheap wood flooring inserts between the wheel runs to keep his back warm. None of his cars keak and he has a skid plate jack (no wheels) so it works for him.

What kind of construction? Reason I ask, if it has a vapor barrier (housewrap) under vinyl siding but has exposed studs inside I'd recommend kraft paper batting type insulation with some sort of inside sheathing. Easy DIY and reasonably priced.

If it's brick, I'll defer to SVreX.

I need to do this with my shop also...but then there are also many places for the air to blow through that need to be fixed also.

At least until I get that done I do have a big ol barrel stove out there to keep things warm

I used iron trusses (very strong). Then I used 2x4's for the ribs on the ceiling and sides, then skinned it with used steel sheets. I have old screw holes from where these were attached to the other building, but I patched those with fiberglass patches. I have no plastic between the 2x4's and steel sheeting. And yes, I have a concrete floor. I have HUGE footers and the pad is 8" in the middle. I poured footers for where I am positioning my lift; they are 36" deep. I used (IIRC) 33 yards of concrete for the 30' x 30' pad. It is reinforced with about 12 million sticks of rebar and I have fiber in the concrete as well.

-Les

What about 4x8 sheets of panel insulation? Huge R-factor and easy to cover a lot of space.

fastasleep wrote: I have HUGE footers and the pad is 8" in the middle. I poured footers for where I am positioning my lift; they are 36" deep. I used (IIRC) 33 yards of concrete for the 30' x 30' pad. It is reinforced with about 12 million sticks of rebar and I have fiber in the concrete as well.

WOW!! You are the MAN!

I built my first garage and Building Code was 4" thick in the center and I went 5" thick. I made a floating slab and the perimeter was over 12" thick.

I used 23 yards for a 24' x 24' and the concrete alone cost me $55 per yard or $1350.39 with tax.

What does concrete run today?

It's more than double that in the rural south right now.

fastasleep wrote: I have HUGE footers and the pad is 8" in the middle. I poured footers for where I am positioning my lift; they are 36" deep. I used (IIRC) 33 yards of concrete for the 30' x 30' pad. It is reinforced with about 12 million sticks of rebar and I have fiber in the concrete as well. -Les

What were you thinking? LOL

The guy can build about anything with leftover parts found at the roadside, but when it comes to a little concrete work, he thinks W is gonna land Air Force One in his back yard!

Hmmm, insulating steel sheet- I have no idea. I'd be concerned about condensation.

And yeah I think Marine One could bounce off that pad and not leave a mark.

OK, getting serious.

Sounds like you've built your shop out of found materials- 2x4 stud walls, steel bar joists above with 2x4 furring runners, and scavenged corrugated steel for the exterior wall sheathing. I'm also assuming your studs are still exposed on the inside. Right?

Did you use that metal on the roof too?

Sounds like a pretty good routine.

Did you by any chance put 1x4 horizontal runners on the walls before the metal, or is the metal attached directly to the studs?

You're going to want to be VERY careful with condensation. That metal sheathing will condensate on the inside when the inside is hotter than the outside. That means the moisture will be in contact with your insulation and your studs. It won't rot your insulation, but it will rot your studs, and the wet insulation will accelerate the problem, as well as rusting the metal from the inside out..

So, you need 3 things- airflow, insulation resistant to moisture, and vapor barrier, or a combination of varying degrees of each.

If you use the spray foam, you will get 1) excellent moisture resistance, 2) great thermal performance, 3) you will move the dew point (where the condensation will form) away from the metal to the inside of the insulation (that's a good thing- it will protect your metal), and 4) a VERY high price tag. Depending on how the metal is attached to the studs, you may also seal it too tight, allowing no breathing room around the studs, which could encourage them to start rotting where they are in contact with the metal (condensation).

If you use the foam panels, you will get 1) very good moisture resistance IF you carefully tape the seams, 2) crappy thermal performance, because although the R value is high PER INCH, the stuff is generally only 1/2" thick (R-3.5- that's crappy). You can use thicker stuff, but it creates other problems. 3) Again, a good vapor barrier, and 4) a relatively high price tag. You will also 5) have a foam wall surface when you are done that is really difficult to hang things on and really easy to damage and loose your thermal and vapor efficiency.

I'd use fiberglass batts. Best bang for the buck, easy to install. I would, however, install it a little different because of your circumstances. You need air flow and a little airspace next to the metal to encourage drying. You can buy styrofoam baffles (designed for insulating tight roof areas) which you can install first against the metal from top to bottom. This will give a little air channel to allow some movement from bottom to top. Or you could make baffles out of folded cardboard. Consider mildew resistant fiberglass batts (special order- a little more expensive, but probably worth it). One more detail. After installing the batts, you need a good vapor barrier on the inside. If they are kraft faced, it will work, but you should be unfolding the paper flange to cover the surface of the stud when you install the batt. Don't just staple the batts to the side of the stud- you'll have 1 1/2" breaks in your vapor barrier at every stud. If the insulation is unfaced you can cover the inside with plastic sheeting (tape the joints).

Something cool about your construction (if you used metal on the roof)- you can run a soaker hose across the ridge and "water" the roof- it will go a long way toward keeping the place cool in the summer via evaporative cooling (like a mister in an intercooler)

One more thing...I have one structural concern with the hybrid wood/metal construction you described. Before you insulate, make sure of your attachment point between the bar joists and the wood walls. There should be a bolt or a metal strap holding down the bar joists, not just a screw or a nail.

Good luck!

Wow! Thanks, that is exactly what I needed to know. You will see it when you come to my house with an empty trailer (not giving anything away here. The metal trusses that I used are not run-of-the-mill units; they are made by a company in Arkansas called Adams' Truss and they are very sturdy. They are used to span huge lengths (mainly for chicken houses). At their manufacturing facility, they have two trusses anchored into concrete with an Edsel suspended between the two; if that isn't structural integrity..........

The idea was that I needed enough concrete to park a dump truck on; but then I made a shorter door at last minute, thinking that my neighbors may not dig me having a Mack pull up for a valve adjustment or service. The concrete should last a long time and it probably won't blow away!

Paul, can you give me a better idea, or link me to a site that shows these fiberglass or styrofoam baffles? I am very interested!

Also, I did use the steel on the roof as well; I just had a lot of it. My dad bid on a building in Oklahoma and won it, but it had to be removed. He relocated the building, but reskinned with new sheets, leaving these for ????. I bought them for $.25/sheet. So I really only had a few bucks in the steel sheeting. I have enough left over to do the lean-to (is that how you spell it?) off of the front. That is a great idea about using water to cool the roof, BTW! I also did not run 1x4's over the 2x4's, but I am thinking that would have been a good thing to do.

Also, what are fiberglass batts?

-Les <-- not a carpenter.

A few years ago we built a cold storage facility that was constructed similar to your building. An outfit came in, sprayed some sort of expand-o-foam, then had some big saw blades they ran over the studs to shave off the excess foam stuff. They then covered the walls with plastic sheeting, then Masonite and/or plywood. Pretty tight building and didn't take a whole lot to cool. It would work the same for heat.It's subjected to temps that range from the 90s in the summer, to well below 0 in the winter. While fiberglass is easy to work with and you can do it piecemeal, the foam stuff is the hot set-up. And it sticks well to the underside of the roof, too.