Attached Garages & Insulation

Homes with attached garages or above underground garages may have interface problems. Un-insulated garages and garage doors can be a source of unwanted energy losses or gains.

If the garage and its exterior door aren’t properly insulated, temperatures can come very close to the extreme temperatures of the outdoor summer or winter air, and the whole thermal comfort of the house can be deeply affected.

Reduce energy costs

There are two approaches to solve the impact of extreme temperatures into the house's living rooms:

- sealing up all the possible thermal pathways between the garage and the house living space.
- insulating the garage exterior walls and its exterior door.

Sealing Air-Paths between the garage and the living Space

Sealing potential air-paths between the garage and the living space (instead of sealing the garage door and eventually the exterior doors) is the right option if the thermal comfort of your garage isn't important to you, or the garage ventilation is a concern to keep into account (vehicle gas fumes may ignite, creating problems that may even reach the explosion risk, in tightly sealed garages).

To seal the air-paths between the garage and the living space you should...

- insulate the floor of the room or rooms above the garage;
- insulate shared walls (between the house and the garage);
- insulate and seal holes in the garage walls;
- fix likely problems with the door between the garage and the home’s living space: replacing it with a good insulated door, repairing potential air-leaks, or improving their energy-efficiency.

ceiling holes in the garage walls

Switches, light fixtures, plugs, etc. and similar systems can be associated with air leaks. Seal them carefully. See: Caulking and Weatherstripping.

On the garage side of the wall, use fire-rated caulk or expanding foam, to seal up penetrations.

Insulating the floor of the rooms above the garage

When insulating the floors over unconditioned garages, do not forget to seal the joints between the header and the sub-floor, and also the top plate and the header joist; also seal and repair possible air-leak paths (holes) in the floor. Insulation should be applied carefully, without gaps.

Replacing or improving the garage door r-value

A double steel garage door, with a proper layer of insulating material (polyurethane…) is a good and affordable option to increase thermal comfort and reduce energy bills caused by attached garages. But there are other choices, obviously.

See: Basics on Garage doors

Insulating Shared Walls

Cold and heated air can be easily transferred between the garage and the home’s rooms via any shared wall.

If non-shared exterior garage walls and the exterior garage door are properly insulated, and you haven't thermal problems with your garage, you won't have thermal problems.

But if that isn't your case, insulating the shared walls is crucial (use fire-rated materials) to get thermal control in the living space of the building.

Door between the garage and the home’s rooms

Any door between the garage and the main parts of the house is a potential air-leak path.

If you are having thermal problems with your garage, insulating that door (and repairing, caulking and weatherstripping possible passageways) will have a positive impact in the living space of the building.

Garage & Insulation materials

If your garage is underground, the insulation materials and the procedures associated with their installation are those involving basements. See: Basement insulation basics.

For other attached garages, the insulation materials and the insulation and sealing techniques are the common ones.

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