Cold garage/woodshop — not sure how I’m going to heat it yet. However, I’m wondering whether I need a vapor barrier if I use fiberglass batting to insulate it. I live in Boston, so a vapor barrier is required when insulating a house (because of the cold climate here). However, we’re talking about the garage, where I don’t think the soon-to-be warm air inside will contain much moisture. Plus, my garage will never be that “tight.” Just warm enough for making some sawdust once in awhile.
Any thoughts? How did you insulate your shops?
– Toolfreak
Replies
You're right about a vapor barrier not being that important. Why instal it if the wind is blowing in around the garage doors? Maybe the vapor barrier is to keep the wind from getting into the wall and lowering the r-value of your insulation? If you have siding on the outside of the wall it has little gaps all over it that let the wind into the wall cavity. Not alot but some, all over it. I guess that is what the vapor barrier is for. The drywall on the inside will keep the wind from coming all the way through the wall. Since i started heating my two car garage the heating bill has gone up $40. It's insulated in the cieling and the walls but the concret slab and two side concrete stem walls are pretty cold. I live in Kansas so it doesn't get too cold.
I could be wrong, but I thought that at least part of the vapor barrier purpose was to keep the insulation from getting damp and decreasing the R-value.
If you build it - he will come.
I could be wrong, but I thought that at least part of the vapor barrier purpose was to keep the insulation from getting damp and decreasing the R-value.
You're right. The vapor barrier on walls is to prevent moisture fro inside the house from condensing on the insulation, reducing its insulating value and promoting rot in the surrounding wood. That's why they go on the inside.
Vapor barriers on the floor are to keep moisture from the earth or concrete slab from permeating the room and rotting the sleepers or joists, and they do make a big difference, drafts or no.
Michael R
Good to know I'm not all wet all the time.
One other thing I thought of. This is something my dad did on his garage. Don't know what kind of garage door you have Toolfreak. My dad has a fiberglass one that loses a lot of heat through it. He ended up taking 1" styrofoam and tying into the back of the door sections with braided wire. He just drilled holes in the alum. ribbing at the top and bottom of each section, about every 3 ft or so. Then cut the styro to wedge fit between the ribbing and tied the wire across it to make sure it wouldn't fall out. It did significantly reduce the cold feeling along the front side of the garage and it doesn't add any significant weight. The only real drawback is that it also decreases the amount of outside light that used to come through the door.
If you build it - he will come.
You're right. The vapor barrier on walls is to prevent moisture fro inside the house from condensing on the insulation, reducing its insulating value and promoting rot in the surrounding wood.
Almost. The vapor barrier prevents humidity from permeating through the insulation, and hitting the cold sheathing on the other side. There, it will condense, soaking the sheathing and nearby insulation, and wreaking havoc with rot and mold formation.
I would use a vapor barrier. The concrete floor will be a source of moisture. Not only what wicks up from the ground, but also what drips off from the car and soaks into the floor.
Any time warm air hits a cold surface or barrier, there will be condensation. The humidity variations in a garage are far wilder than in a house. For the low cost, it's worth not having to replace whatever rots from the moisture.
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