Here is what the roof of my shop looks like. I was wondering if I could run 2” foam on the 2x4’s that run across the roof to help with heating. I was going to just rail it or screw it to the 2x4 leaving a 3.5” air gap. So you think I would have any moisture problems? My walls are all insulated and covered with tin but I have nothing on the roof. Just trying to make it easier to get it comfortable for skinning and working fur. Plus working on the tractor etc. I’d love to have it spray foamed but I can do the foam board for about $1k and that’s in my budget this year.

Do you have any vapor barrier under metal roof now. Do you have any condensation problem with moisture dripping from roof inside building?

No vapor barrier

Bad thing is Im never out there in the morning so not really sure if it has a drip. I do see stains on some of the 2x4 but not sure if that was before I put the concrete in.

Looking at getting a Sunfire heater. And hoping to make it more energy efficient

IMO your plan will help hold some heat in but think you will have moisture on top of insulation. That moisture will need to go some where out at roof edge. I would be afraid of mold on wood rafters without good air movement. How high is this roof from floor of shop?

The walls are like 9.6 high since the concrete went in. The ridge is Im guessing is 15-16’ high? I am open to ideas. Just trying to get something to work but don’t want mold or not.

Sorry i cant see any photos, is it a metal roof?

Spray foam is what you need. Condensation comes from the air inside of the building. The foam adheres to the metal, preventing condensation from reaching the underside of the metal roof.

^^^^^^^THIS^^^^^

The foam board will act as a vapor barrier if it’s faced foam and you tape the seams. You may still need to blow, or spread by hand if small area, a few inches of insulation on top of the foam to keep heated air from reaching metal and causing condensation. Un insulated attic area should be well vented to keep under side of metal as close to outside temp as possible.

That’s how we did the heated side of our building in Canada anyway, 1.5” aluminum faced foam with 12” blow in on top.

Yes the roof is metal. Sorry can't get the pic to load. Only complaint about this forum it is terrible to load photos on.

I am thinkig about doing a flat roof like what you show. I was trying to do the roof to leave the truss exposed since my trusses are 10" apart that way I had some height up between to be able to use it. But doing a flat roof wouldn't be too hard either and I would still have a 9'6" ceiling height.

Yes, spray on foam is the best solution in your situation but of coarse the thing you wanted to avoid was high cost.

I agree spray foam would solve the problem. I have it in shop and shed, walls and ceilings. Love it but it’s gotten crazy expensive. Also, by closing in the ceiling at 9’6” you will heat the area up a lot quicker, and cheaper.

Been alot of complaints with spray foam though. Look into it, i believe alot will absorb moisture over time and rust metal trusses and supports.

That doesn't surprise me. Moisture needs to evaporate or move on to an exist and air needs to be involved in all cases.

Question Sasquatch, I would think mold would be an issue using foam with wood structure and wood material. I can't imagine it not having a change to grow with moisture in contact with any wood product. What do you think?

I know if you foam a shop that has shingles, you will burn up shingles at a high rate of speed. Like within a few years. There needs to be breathing room between insulation and a sheeted roof. As far as the mold, im not real sure on that side of things but i would think so. Anywhere there is moisure black mold can start.

I think you would be better off to bite the bullet and put an insulated ceiling in. Then put vents in the attic to circulate air to keep it dry.

There are two kinds of spray foam. Closed cell and open cell. Open cell can absorb moisture and technically is not vapor proof. Closed cell does not absorb moisture and is considered a suitable vapor barrier. I wonder if the complaints you have heard are from open cell foam? I have no complaints on the closed cell and its been in shop for nearly 20 years and 10 yrs in shed.

^^ that said I would still go enclosed ceiling in sigpros case.