Keep my garage moisture free
Ok guys, after some additional research I think I have a plan for what I am going to do. I think I am going to use 1 inch polyiso foam boards (foil on both sides). And place them between the beams, while foil taping the exposed metal on the beams to prevent condensation (does that sound right?).
Once the foam boards are up, I plan on using a thick plastic vapor barrier to cover the foam board insulation. I’ll be insulating the walls first, and then the roof. Once the building is fully insulated, I plan on installing a wood burning heater along the back wall (the wall across from the large doors) towards the center of the wall so it can heat the shop evenly.
IMO this should be a relatively simple, cost effective way of insulating my shop.
what do you guys think?
You'll want a layer of foam over each exposed metal member, otherwise those cold beams will still sweat inside.
The idea of leaving a gap and securing directly to your framing is a good one, but the air space will act more like a "rain screen" and won't necessarily make the wall better insulated.
Since you have surface mounted electrical, I'd stick to your plan of going between beams (and overlapping a second layer over each beam). Later on you can add another layer and a few years later another layer... Etc.
Don't bother with the interior vapor barrier. The foil facing of the foam will act as one already (usually) and having the ability to diffuse any random moisture is still a good thing. Some sort of durable wall board would be a good idea to protect the foam boards. Plywood, osb, hardboard, drywall, concrete board, doesn't matter a ton, but any all-wood materials are at greater risk for fire than drywall (which actually produces moisture/water as it gets heated) or concrete board.
Since drywall sucks up standing water and is easily damaged, I like thin cement board for the first 4' or so of a garage wall.. But that's just me.
Another option would be to layer metal siding on the inside.. Durable, easy to replace, no mud or mortar to install it and can be taken down to augment your insulation in the future. Also less prone to fire/burning. Even corrugated metal roof panels could be used, even if only partially sheathing the wall.
Just my $.02
