The room above my garage is always cold. Who do I call?
Usually, start with
Home-performance / insulation professional
If a room above the garage is consistently colder than the rest of the house, a home-performance or insulation professional commonly evaluates the floor assembly over the garage, insulation continuity, air leakage, and the thermal boundary between the garage and the room above.
Change course if
The room's heating supply seems weak or absent
An HVAC professional may also be relevant when airflow or heating-system distribution appears different from nearby rooms.
The problem began after remodeling or insulation work
A building-performance professional can evaluate how the altered assembly is performing.
You also notice garage odors or air moving into the room
Air-sealing and building-performance evaluation may be especially relevant when the garage-to-house boundary appears leaky.
Who handles what
Insulation / building performance
Evaluates insulation continuity, air leakage, and the floor or ceiling assembly separating the garage from living space.
HVAC
Evaluates heating-system delivery, registers, ducts, and room-by-room temperature distribution.
What might be happening
A room over a garage has more exposure to outdoor or unconditioned temperatures than many interior rooms. Insulation gaps, air leakage, duct conditions, and heating-system distribution can each contribute to a persistent temperature difference.
Useful things to notice
Whether the floor itself feels unusually cold
A cold floor can be useful information about the assembly over the garage.
How the room compares with nearby rooms
Temperature and airflow differences help a professional understand whether the condition is localized.
Whether there are drafts or odor transfer
Air movement can be relevant to the integrity of the garage-to-house boundary.
Before you call
Note when the room is coldest, whether supply registers are open and delivering air, and whether the floor or particular walls feel especially cold. Photos of the garage ceiling and any accessible insulation can be useful.
Before you fix the visible symptom
Adding a space heater or replacing visible insulation may improve comfort without identifying whether the limiting condition is insulation, air leakage, or HVAC delivery. A targeted evaluation can help separate those possibilities.
References
U.S. Department of Energy. Building America Webinar: Air Sealing and Insulating a Floor Above an Unconditioned Garage.
U.S. Department of Energy. Insulation and Air-Sealing Essentials.
ENERGY STAR. Seal and Insulate with ENERGY STAR.
Building Science Corporation. Westford Modern Colonial Deep Energy Retrofit: Isolating an Attached Garage.