I'm hoping one day before I'm dead I can afford to have mine spray foamed.
Shop insulating advice
- Thread starter DentalDart
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Lets just start with did you put a vapor barrier under the concrete?
If you didn't, you damn sure don't want to envelope the top side.
If you didn't, you damn sure don't want to envelope the top side.
Phreakish
Well-Known Member
The closed cell foam he's using is already a vapor barrier, even more so with the foil. As others have said, stacking barriers is not a good Idea. Depending on what you use to insulate the ceiling, you may need or want one there.
The peicemeal approach should work well with all the gaps foamed or taped or other approaches to limit the pumping, but no envelope is ever perfect. Spray foam gets close, but many still "leak" air because of cold laps or pinholes. It's a shop/barn and not a house so the risk is already lower. If doc installs a mini split, he'll be able to normalize the temperature enough to avoid pumping moisture through the walls.
The studs will definitely bridge and conduct heat, but houses were built with thermal bridges to the inside insulation for decades, still are. It would matter a ton more for a living space than a shop. Personally I'd be trying to stagger studs or do something to improve the insulation performance, but the juice may not be worth the squeeze either. I doubt the goal is to keep the place at 75 when it's 5 below after all.
I'm curious what the plan is with the trusses, because I can't imagine it would be doable unless the whole roof and current trusses were pulled out and a whole new roof assembly installed. Trying to field convert standard trusses to scissor is a tall order and huge risk. Trusses typically need an engineers stamp and field built aren't really a diy endeavor for someone who hasn't trained with someone with experience. Not that it's impossible, it just isn't simple either. The scissor configuration will need to be designed to work with the roof design and the fastening at the splices are critical. Mending plates aren't rated the same as the connectors used by truss makers. The hydraulic tooling used to press in truss connectors also isn't super cheap.
The gaps at the roof to the walls are going to be a challenge. They do sell sealing strips that match the metal roofing contours and you could mount those to a 2x and then nail them in to close everything up decently before coming back and spray foaming the small gaps. Without exterior baffles, soffit venting is asking for birds and mice to take up residence in the attic. Gable venting for a shop should be fine, worst case you'll want an attic fan. I'd be tempted to install a "whole house fan" anyway, since it would probably be handy - especially in the summer. It would also provide a way to clear dead air in the attic on occasion.
@dowboy1970 makes a good point, if there's no vapor barrier under the slab, you're likely to get moisture wicking up through the concrete which will raise the interior humidity every time you warm it, and then you'll get condensation every time it cools off. There are products which can "seal" or cure concrete (not paint, paint won't stop moisture!) and can help lower how much moisture can wick through. It's also cheap. I forget what the products are called but they advertise that they seal and harden concrete further. A good moisture test is to put down some plastic and weigh down the corners for a few days. If the concrete is dark or wet when you lift it after those few days, then you're going to have trouble. No dark spot? You'll probably still get some moisture, but not too much to deal with. I've seen people install radon fans to help alleviate moisture issues through a slab with decent results, fwiw. Dehumidifiers can also work well when the moisture load isn't excessive.
The peicemeal approach should work well with all the gaps foamed or taped or other approaches to limit the pumping, but no envelope is ever perfect. Spray foam gets close, but many still "leak" air because of cold laps or pinholes. It's a shop/barn and not a house so the risk is already lower. If doc installs a mini split, he'll be able to normalize the temperature enough to avoid pumping moisture through the walls.
The studs will definitely bridge and conduct heat, but houses were built with thermal bridges to the inside insulation for decades, still are. It would matter a ton more for a living space than a shop. Personally I'd be trying to stagger studs or do something to improve the insulation performance, but the juice may not be worth the squeeze either. I doubt the goal is to keep the place at 75 when it's 5 below after all.
I'm curious what the plan is with the trusses, because I can't imagine it would be doable unless the whole roof and current trusses were pulled out and a whole new roof assembly installed. Trying to field convert standard trusses to scissor is a tall order and huge risk. Trusses typically need an engineers stamp and field built aren't really a diy endeavor for someone who hasn't trained with someone with experience. Not that it's impossible, it just isn't simple either. The scissor configuration will need to be designed to work with the roof design and the fastening at the splices are critical. Mending plates aren't rated the same as the connectors used by truss makers. The hydraulic tooling used to press in truss connectors also isn't super cheap.
The gaps at the roof to the walls are going to be a challenge. They do sell sealing strips that match the metal roofing contours and you could mount those to a 2x and then nail them in to close everything up decently before coming back and spray foaming the small gaps. Without exterior baffles, soffit venting is asking for birds and mice to take up residence in the attic. Gable venting for a shop should be fine, worst case you'll want an attic fan. I'd be tempted to install a "whole house fan" anyway, since it would probably be handy - especially in the summer. It would also provide a way to clear dead air in the attic on occasion.
@dowboy1970 makes a good point, if there's no vapor barrier under the slab, you're likely to get moisture wicking up through the concrete which will raise the interior humidity every time you warm it, and then you'll get condensation every time it cools off. There are products which can "seal" or cure concrete (not paint, paint won't stop moisture!) and can help lower how much moisture can wick through. It's also cheap. I forget what the products are called but they advertise that they seal and harden concrete further. A good moisture test is to put down some plastic and weigh down the corners for a few days. If the concrete is dark or wet when you lift it after those few days, then you're going to have trouble. No dark spot? You'll probably still get some moisture, but not too much to deal with. I've seen people install radon fans to help alleviate moisture issues through a slab with decent results, fwiw. Dehumidifiers can also work well when the moisture load isn't excessive.
The main issue with metal clading is it sweating when its cold out and warm in. When i have built alpine houses it literally rains on the inside, so the better you get the insulation the more sweating you will get. Thats why when we metal clad buildings we create a rain screen for the water to run down behind the cladding yet not been in the building envelope.
The roof really needed to be wrapped, or a insulated blanket used to stop the sweat entering the building and instead running out of the building envelope.
We frame then wrap the home, batten the frame and then metal clad, it also creates a thermal break which adds to the insulation.
You can also get sectional doors from europe that fully seal for dust and cold as well as being insulated as the door ia a week point. As seen in a home we just finished. Bad pic but great bit of gear however you pay but thats what u need for cold conditions however you can also by thermal panels that slip into traditional sectional doors
The roof really needed to be wrapped, or a insulated blanket used to stop the sweat entering the building and instead running out of the building envelope.
We frame then wrap the home, batten the frame and then metal clad, it also creates a thermal break which adds to the insulation.
You can also get sectional doors from europe that fully seal for dust and cold as well as being insulated as the door ia a week point. As seen in a home we just finished. Bad pic but great bit of gear however you pay but thats what u need for cold conditions however you can also by thermal panels that slip into traditional sectional doors
The amount of thermal bridging he will get from the studs will be near bugger all as timber one of the best materials to use that will not bridge the outside in, i think staggering big over kill for a shed. His biggest issue will be stopping the sweat causing damp or mold. As really all it needs is to be wrapped, traditional insulation, plaster and a heating unit as doesnt need to hold temp like a home. But its all back to front
Mopar Momzee
Well-Known Member
So on the subject if i was to do it again spray foam well worth it but it is vary flammable so spray with spray retardant paint. also did ridge vents but sealed them up because of spray foam so that was a cost i spent but didnt need to.
DO NOT sandwich your walls between 2 vapour barriers.
Lot's of good info here. Good luck with your build. 
I figure people's likes and opinions of how to build and insulate barns, garages is like peoples opinion of Bar B Q!!!!! If you look at what 99% of the locals do in their home area, that is always a good indiction. But I learned long ago, never move to a new part of the country and try to tell the locals that they do it all wrong!! ha
I built 2 small pole barn homes in S W Mo down the road ther Doc. Maybe I did it all wrong. First one was 900 sq ft. Yep small but what I could afford that day. On a slab 4 inches of packed gravel, 4 inch concrete on top for floor. Ceilings were 8 ft. interior, poles were 5 x 5, tin screwed to 2 x 4 perlins,with T Vec under tin. 6 inch bates for wall insulation and cellulose blowed into the attic. Walls/celings were sheetrock. Roof had turbin type roof vents to let out hot air. Only heat was small wood stove. No AC. We were tough/sorta. No sweating, no issues.
Second pole barn home was 1500 ft. built on OSB sub floor. Roof had a 1/8 in thick vapor barrier under tin,Ty Vec under outside sheet metal, front of home was cedar lap siding. Same deal, except poles were 6 x 6, car siding ( tongue n groove pine) and sheetrock walls/ceilings., and I did 6 in. bates in attic. blowed in would have been better, but figure I would do that later. Insulation bates were all 6 inch. Roof had vents and gable ends also to let out attic heat, I heated with wood stove only and cooled about 1000 sq ft of it in summer with only a wall unit and never turned it on before noon.. Warm in witer and cool in summer. No issues.
My "garage" was a 3 sided shed open to th SW. Just tin on side and roof. Dirt floor. Yea it occasionally would sweat just a little if conditions were right. But it held 8 cars!
Before all that I had a 50 x 100 foot arena in NW Mo, the end had 12 x 12 stalls and concrete alley, 24 50. Above the stalls and alley was a wood celing and insulated with wheat straw bales, the walls had NO isulation. Heated with overhead propane furnace. Never any sweating. Cool insummer and propane was cheap!! BUT...I had another stall barm like 36 ft wide with 12 ft box stalls and 12 ft concrete ally. No isulation at all. That barn concrete floor and tin walls would sweat like crazy! It was a foaling barn used just a few months when needed. Sweaty concrete an be slick!
I built 2 small pole barn homes in S W Mo down the road ther Doc. Maybe I did it all wrong. First one was 900 sq ft. Yep small but what I could afford that day. On a slab 4 inches of packed gravel, 4 inch concrete on top for floor. Ceilings were 8 ft. interior, poles were 5 x 5, tin screwed to 2 x 4 perlins,with T Vec under tin. 6 inch bates for wall insulation and cellulose blowed into the attic. Walls/celings were sheetrock. Roof had turbin type roof vents to let out hot air. Only heat was small wood stove. No AC. We were tough/sorta. No sweating, no issues.
Second pole barn home was 1500 ft. built on OSB sub floor. Roof had a 1/8 in thick vapor barrier under tin,Ty Vec under outside sheet metal, front of home was cedar lap siding. Same deal, except poles were 6 x 6, car siding ( tongue n groove pine) and sheetrock walls/ceilings., and I did 6 in. bates in attic. blowed in would have been better, but figure I would do that later. Insulation bates were all 6 inch. Roof had vents and gable ends also to let out attic heat, I heated with wood stove only and cooled about 1000 sq ft of it in summer with only a wall unit and never turned it on before noon.. Warm in witer and cool in summer. No issues.
My "garage" was a 3 sided shed open to th SW. Just tin on side and roof. Dirt floor. Yea it occasionally would sweat just a little if conditions were right. But it held 8 cars!
Before all that I had a 50 x 100 foot arena in NW Mo, the end had 12 x 12 stalls and concrete alley, 24 50. Above the stalls and alley was a wood celing and insulated with wheat straw bales, the walls had NO isulation. Heated with overhead propane furnace. Never any sweating. Cool insummer and propane was cheap!! BUT...I had another stall barm like 36 ft wide with 12 ft box stalls and 12 ft concrete ally. No isulation at all. That barn concrete floor and tin walls would sweat like crazy! It was a foaling barn used just a few months when needed. Sweaty concrete an be slick!
This is pretty much exactly what I will be doing but without all the “properly designed” stuff, learneded how to do it via the YouTube… lol
Or this could make things pretty easy… chicken barn trusses taken down. Rip off metal building roof, install new trusses and install new roof lol.
@Phreakish
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I have no clue about that question. This pole barn has been here for a couple of years… I was probably 10 when it was built… I just bought the place in August.
I assume the concrete isn’t thick enough for a lift and I’ll have to add some more to thicken it up before installing a lift… or could always just say YOLO?
I’d love spray foam, but I wouldn’t love the cost of spray foam. Maybe my next building I can do with heated floors and spray foam on the walls/ceilings…. But for now I’m doing the cheap DIY way to hold me over.
I also don’t need a house level insulation, just gotta knock the cold off so my titties aren’t so hard they could cut glass.
You will be a LOT better off than the dude in the video in that I presume that you will place the lift so that the vehicle is perpendicular (rather than in line) with the trusses, so that you will be placing the vehicle at the high part of the scissor trusses. When he does all this work the ends of his vehicle on the lift will still be really close to the ends of the trusses.
I noticed that his scissor trusses are made from 2x6s instead of 2x4s...
Phreakish
Well-Known Member
So long as you can get timber members long enough to not require a splice, that might work. I'd still try and get an engineer to size some scissor trusses though. Hand him $100 to make up for not buying them and I bet your local (non corporate) lumber yard would Calc something up for you to use as reference. You might even find some illustrations of off the shelf designs that match your roof pitch that you could use as reference instead.
It's not impossible to do the calcs yourself if physics was ever a strong suit. I'd still want someone to double check my numbers though.
It's a big deal because you don't find out it wasn't right until snow or rain or leaves brings the barn down.. Or even worse, it gives way while hanging insulation and ceiling panels.
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And just raise the roof where needed. Not the whole shop.
And maybe partition and just do heavy insulation in the lift area.
Save on your heating that way as well.
And maybe partition and just do heavy insulation in the lift area.
Save on your heating that way as well.
Phreakish
Well-Known Member
Fewer and longer truss elements mean the section area of the elements needs to be larger.
That garage looks a sight smaller than Doc's by my eye too. Could just be perspective though.
I'm no architect, just an intimate knowledge of the physics so I can fake it but there no replacement for industry experience..
Phreakish
Well-Known Member
It may not be practical, but I'd be tempted to get some beams and shoring and try to jack the whole roof up 3-5ft and make the walls taller. I've seen it done, but there's enough foam sprayed in there now it would be a losing proposition, lol.
One thing is for sure, pulling the roof and replacing the trusses and metal would be waaaay easier, especially if you get trusses from a truss company that can set them with a crane. You could even let the trusses run past the wall and produce an overhang that would keep a lot of the moisture off the metal walls and reduce condensation inside. Here in the Pacific Northwest there's a reason almost all buildings have a substantial overhang...
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My Father IL built himself a 25 x 35 standalone shop and had it sprayed, 12k lift and lights like a prison then he installed a used 3.5 ton outside unit and used his old shop for storage for whatever cars he is not working on.
Doc, I would be cautious of used trusses.
Unknown design, unknown environmental conditions, etc.
IMHO
You could get an engineer to design a box area in the trusses where you would put a lift under.
That way you only modify 2 or 3 trusses vs all the trusses.
Unknown design, unknown environmental conditions, etc.
IMHO
You could get an engineer to design a box area in the trusses where you would put a lift under.
That way you only modify 2 or 3 trusses vs all the trusses.
jos51700
Green Bearing thread connoisseur
Have you looked at Froth-Pak at Home depot? It might be cheaper than buying the wee cans. It's what we use in the corner and roof joints of our spiral enclosures. They're 5" thick metal insulated panels, and I can't see the joints on a FLIR camera if they're properly Froth'd.
I’ll call a truss company tomorrow and maybe get some quotes. I also agree, it would be way easier to pay someone to do it… but usually easier comes at a cost.
I know I sound cheap, but really this is an old shop, one that has been around a long time. I don’t need to dump 40k updating it when I could build a new one for 50-60k, insulated and all.
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I looked at them but they are like 400 bucks, I figured I could get all the spaces sealed with the little cans and I think it’ll be close with what I got, and I maybe spent around 100 for spray foam cans. I’ve only used 4 small cans and 2 large ones and it has gotten almost half of the building done. But only about 1/4 of the roof to wall opening. I still have like 5 or 6 cans of spray left. If I need a significant amount of spray after using all this I may spring for a Froth-Pak.
Phreakish
Well-Known Member
The only reason I've piped up is to maybe give you some ideas as you go and things to think about in case it fits with you goals.
Your plan will work, but there's potential for issues depending on your exact climate. The best I could do would be to look st maps and regional hvac chats, but that doesn't fill in all the blanks for a perfect job. If something does happen, it won't be anything that can't be fixed later though. So, keep on it and address **** as it comes up. I'd rather have to spray every peice of steel in the shop with fluid film than freeze my nuts off doing a January cam break-in again!
I've been down similar roads before and burned an absolute ***-ton of time and money trying to save things not worth saving a while destroying my back and shoulders. At some point you sit back and ask "why didn't I!?".. Or not, ymmv!
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