I have a 20x14' workshop in my backyard. When I had it build, I had the installer place rigid insulation form under the concrete slab but everything else was not insulated. Since then, I've installed insulation batts in the walls and a vapour barrier and then drywall on top of that. It is till cold inside since cold air from the outside can enter in through the ridge vent at the top or the 8 soffit vents that line the side. This year my plan is to insulate the ceiling as shown in the middle picture below. There will be an air gap between the roof and the insulation, then another vapour barrier and a radiant barrier on top of everything.
I'm hoping with some space heaters the inside will now remain warm when the outside is cold. I am worried what will happen in the summer though. I don't want the inside to turn into an oven so I'm trying to think what to do to prevent that from happening. I could put an AC unit in one of the windows for the summer months to cool the inside ... but is there another way? I don't want to punch any holes in the walls (through the insulation) because I'm worried birds or critters are going to try to climb into the workshop during the winter months.
I was wondering if I could put some fans or vents in the ceiling insulation to allow hot air to escape out through the soffit vents or the ridge vent.... would that work?
Any suggestions would be greatly appreciated!