A bedroom or office over an unheated garage can be cold even when the rest of the floor feels fine. The garage ceiling is also the floor of the room above. Heat can move through that assembly, and air can travel through gaps at the perimeter or through joist cavities that extend into the house.
Map where the room feels cold
A cold stripe around the edges may point to the rim or a gap at the outside wall. A large cold area across the floor may point to thin, displaced, or poorly fitted insulation. Check whether the problem is worse when the garage door opens or during windy weather. Note whether the room has the same heating output as nearby rooms.
Keep air sealing and insulation continuous
A contractor should identify the air barrier and check where it connects to the surrounding walls. Insulation performs better when it stays in contact with the underside of the subfloor, without gaps where air can move around it. If joists run from the garage into the house, ask how those cavities will be separated.
Maintain the separation between the garage and living space
The work should preserve the required protection between the garage and the room above. Ask how the contractor plans to access the floor cavity, treat wiring and other penetrations, and restore the ceiling finish. Garage exhaust or odors inside the house deserve prompt investigation. Keep vehicles off when parked inside.
What to include with your quote request
Send the approximate size of the room, tell us whether the garage ceiling is finished, and describe the cold spots. If there is plumbing in the floor, mention it so it can be considered before the work is scoped.
