Sealing up a metal shop building. Need advice.

[Dan Coker]

So I would like to make some upgrades to my shop cooling system which I run in the summer when it gets hot. I currently have a 5 ton system that dumps through an elbow atop the air handler. Of course I understand the risk and difficultly in having an air conditioner in a wood shop and I am fine with it. I have dust collection everywhere. Plus I have the unit as far from the cutting areas as possible. I basically got this system for a little of nothing so if it goes bad then I will replace it with another used one.

My entire shop is insulated with rolls of insulation on all walls and ceilings. My building is a metal covered shop framed out of red iron. It’s a rather odd shape but overall not including the separate finishing rooms, sanding and equipment rooms the main part of the shop that I am trying to cool is roughly 5,000sq/ft or so.

My questions pertain to how I can better seal up the ceilings where they meet the walls and where the walls meet the floor. My shop is old and some of the rolls of insulation are in bad shape and hanging off. Being that my shop is framed with red iron and steel and covered with typical shop metal on the outside walls and roof there are noticeable gaps around the base of the walls and at the top of the walls where they meet the ceiling. I figure that I could cut down all of the damaged/hanging pieces of insulation and replace those areas fairly easily. What I am less sure about and seek advice/opinions on is what to do around the tops of the walls all the way around the building to better seal that up (and at the base of the walls too) so that I can get my shop to cool off better this summer? I originally tried to use spray foam in a can at the tops of the walls but the small area that I experimented on to try this method didn’t work and actually damaged my roof because where I sprayed it the foam expanded and pushed the metal roof up causing leaks when it rained. Any advice or suggestions on how to do this?

[Jim Becker]

Dan, I do believe that spray foam is the right solution, but you can't use the typical hyper-expanding version for the reason you state. If budget was no object, I'd strip out the old hung insulation and have a professional do a proper closed cell spray foam insulation which would not only provide you with sealing/moisture barrier, but also stiffen up the whole structure noticeably. For spot fixing, I'd still use foam but again, use the type that is designed for insulation work rather than the expanding type in the small cans. You should be able to get a DIY tank kit to do the job which will be more cost effective than spray bomb cans and put out material that's appropriate for the job.

[james manutes]

I think this could be a pretty large undertaking , potentially . Sounds like the fiberglass batts are exposed with a not very good metal exterior , in terms of air infiltration . "flash and batt" is when guys apply 1" to 2" closed cell foam , then add insulation , perhaps OSB or other wall coverings . The big benefit is the air tight envelope created by the foam , which will also make it less likely to rack or move . The downside is IF you need to remove or replace the metal , it's a PITA . 5000 sq. ft. is a big shop , so long term , what do you think the plan is ?If the majority of the insulation you have is still good , that help's alot . Lots of labor , but it's done often . Shore up the exterior first ( missing screws- bird nests - ETC. ) , then spray .

[james manutes]

Hey Dan , what is your location ? A 5 ton AC has to cost a lot to run . Have you looked at Mini Split systems . That is another area that can become a "rabbit hole " of discussion , but I love mine .

[Andrew More]

I agree with Jim and James. First I got a spray kit from Foam-it-Green online. I don't think it matters much where you get your kit, they all come from the same factory, and then distributed through a number of channels. If you can spray paint, you can spray foam, though all the ladder work could be killer. I applied 2" of close cell to the top of my 2 car garage and noticed a massive difference. Also sealed up a number of air gaps that were no big deal when it was just used to store cars.

I also have a top of the line mini split. I got a screaming deal because I know an HVAC dude, but if I hadn't I'd probably get one of the DIY kits. They're relatively easy to install if you're okay with running electricals. With the minisplit installed I see no difference in my power bills, since it's so efficient.

[Jim Becker]

Andrew, I've also seen pretty much zero impact on energy usage since putting my MiniSplit into service two years ago this month. Actually, it's gone down because of a well pump replacement, so it's hard to know the exact impact for sure. But at 20 SEER, it's darn efficient for cooling and I've been extremely pleased with heat through the colder months. I don't bother to set back from my heating or cooling temperature because my insulation is pretty good and the thing barely runs. But this is a digression from the OP's concerns about sealing the building. Funds to replace the available HVAC unit may or may not be a challenge.

[Dan Coker]

I think this could be a pretty large undertaking , potentially . Sounds like the fiberglass batts are exposed with a not very good metal exterior , in terms of air infiltration . "flash and batt" is when guys apply 1" to 2" closed cell foam , then add insulation , perhaps OSB or other wall coverings . The big benefit is the air tight envelope created by the foam , which will also make it less likely to rack or move . The downside is IF you need to remove or replace the metal , it's a PITA . 5000 sq. ft. is a big shop , so long term , what do you think the plan is ?If the majority of the insulation you have is still good , that help's alot . Lots of labor , but it's done often . Shore up the exterior first ( missing screws- bird nests - ETC. ) , then spray .

Thanks for the reply James. The metal covering the building on the walls and roof is in good shape. As is most of the fiberglass insulation on the ceilings and walls. I would say that on the ceilings 75% of it is great. On the walls that number is around 95%. Long term I would like to be able to get the shop cooled off in our very humid summers. I am not interested in changing the existing a/c unit out.

i have looked at spray foam kits. I just don’t know if I would need to tear out all of the fiberglass and spray the entire ceiling, which I won’t be able to do this year as that would cost over $10k, or if I could possibly go around the perimeter and spray all places where there is missing or damaged fiberglass and all of the places where the walls meet the ceilings. I could likely afford to do that now. I feel perfectly comfortable spraying the foam myself. I have a local guy that gets $1.45 per square foot installed. I wouldn’t mind doing a drop ceiling in the future but for now I need to figure out how to seal it up and get the ability to cool the shop off.

[Jim Andrew]

Dan, a steel building is hard to cool without a ceiling. You should talk to your local ceiling company, as they often remove suspended ceilings from buildings being renovated. That old ceiling goes to the landfill. They put up a new ceiling after the remodel, and if someone needs a ceiling like you, can make you a great deal on the one they remove. I have salvaged 2 ceilings, put one in my shop, gave away the extra parts, and when I did my addition, got another ceiling, and wound up selling the extra parts. Also got a lot of 2x4 troffer fluorescent lights, converted them to LED. Have about 24 troffer lights in my shop.

[Andrew More]

I feel perfectly comfortable spraying the foam myself. I have a local guy that gets $1.45 per square foot installed.

Depending on the price you get, this might be something you can DIY, but really don't want to. I do almost all of my own work, but spraying foam is miserable, and doubly so on top of a ladder.

The issue is that the room needs to be at 65-85 degrees for the mix to work. Then you need to put on a complete sealed body suit, or you will get it on you. Then you need to climb up and down a ladder, which is going to make you VERY hot, sticky, and fog the glasses.

Jim I was told my Minisplit had a SEER rating of 32. It doesn't seem possible with conventional ACs topping off at 16-18, but there you go.

[Jim Becker]

Jim I was told my Minisplit had a SEER rating of 32. It doesn't seem possible with conventional ACs topping off at 16-18, but there you go.

Wow...I've not seen them that high. Quite a few at 20 and a few at 22, but I haven't seen higher. But then again, I haven't looked, either.

[Andrew More]

Wow...I've not seen them that high. Quite a few at 20 and a few at 22, but I haven't seen higher. But then again, I haven't looked, either.

I've had this since 2017, and according to Fujitsu it's "Up to 33".

https://www.fujitsugeneral.com/us/pr...su12rls3y.html

[james manutes]

Metal roof's get very , very , hot . They then transfer those BTU's into the building . If the roof has plywood decking w/ metal above , that's helpful . I'd try to come to a long term plan , as to not revisit this issue again . Believe me , I love to do it myself and cheaply if I can . Another option is rigid foam panels for the majority of the space , and spray the seams to make it air tight . At a minimum , spray the seams . That's hard without taking the batt's down first . I hope you find the result you are looking for , with whatever you choose .

[Jim Becker]

james, this is a "classic" remediation of the problem conundrum...try to spot-fix it or invest in a total do-over the correct way. Tough call and it involves money. The OP's insulation was likely adequate for the original purpose when originally installed, but either time hasn't been kind to the material or the original install wasn't quite what it needed to be to avoid the gaps.

[james manutes]

Dan , one last thought . When I installed my Mini Split , the amount of water coming out of the drain tube was Stunning! Reducing humidity is as important as the cooling of the air I believe . After 2-3 days the unit scaled back , and didn't run as hard . That's the beauty of a Mini Split . If your shop stay's "humid" , I know it would help .