How do I keep my garage warmer in winter?

Seal first, then insulate

The fastest way to a warmer garage is to stop cold air getting in; the insulation comes second. The Department of Energy's comparison is the useful one: "Think of insulation as a sweater — it can keep you warm when the air outside is cold, but it does not really block the wind."^[1] Sealing is the windbreaker, and it is cheap. Air sealing is one of the most cost-effective ways to improve the comfort and energy efficiency of your home.^[1]

Your garage door is likely the largest opening in your home,^[2] and its edges are where most of the winter air comes in. Even a small gap can let hot or cold air seep into your garage.^[2] If you have already insulated and it is still cold, start with why a garage stays cold after insulating.

Do these before the first hard freeze

Inspect the edges. Clopay recommends that you regularly inspect the door's perimeter, threshold and any windows for signs of air leaks.^[2] Do it in the fall: close the door, switch the garage lights off in the afternoon and look for daylight along the bottom, sides and top and across the joints between sections.

Replace a worn bottom seal. Disengage the opener before beginning work, raise the door to the open position and put C-clamps in both tracks directly below the door and tighten them.^[3] Then swap the seal. Match it to your door, because garage doors are manufactured with varying types of weather seal retainer designs, so the replacement has to be the right type for your retainer.^[3]

Weatherstrip the sides and top. If the strip along the jambs and header is cracked, flattened or pulled loose, replace it. Use weatherstripping or spray foam insulation to seal any gaps you find.^[2] Weather-stripping can be tension seal, felt, reinforced foam, rubber tape, aluminum or stainless steel door sweeps, metal gaskets, bulb or fin seals, and other types of interlocking metal channels.^[1] For the walk-in door, a sweep along the bottom and a strip around the frame usually cure most of the draft.

Check windows and penetrations. Caulk around garage windows and where pipes or wires pass through the wall.

Then insulate the door

Once the edges are tight, insulation pays off. In the winter, insulated garage doors help retain warmth, decreasing the load on your home's heating system.^[2] A foam-panel kit is the usual do-it-yourself route; how to insulate a garage door walks through it, including the balance test afterwards. If you are weighing the spend, see what garage door insulation costs in Virginia and whether insulating is worth it.

Habits that keep it warmer

• Close the door promptly. Do not leave it open while you load the car or let the engine warm up.
• Never warm the garage by idling the car. Do not idle the car in a garage, even if the garage door to the outside is open, because fumes can build up very quickly in the garage and living area of your home.^[4]
• Keep the seals clean and flexible. Wipe dirt off them so they close fully.
• Re-check in midwinter. Cold stiffens rubber and shifts weatherstripping; a quick feel along the edges on a windy day shows what moved.

Heat for the garage

Heating a garage is a different job from sealing it, and it carries risks that the rest of this page does not. If combustion appliances do not get enough oxygen, they will operate inefficiently and may release dangerous gases such as carbon monoxide into the home.^[1] The EPA advises having fuel-burning appliances, including gas or kerosene space heaters, inspected by a trained professional at the beginning of every heating season.^[4] A permanent heater needs a licensed professional (see below).

Stop and call a pro if

• You want a permanent garage heater. Gas lines, vented combustion appliances and dedicated electrical circuits are work for licensed pros, and the vent and air supply have to be right. Ask for the contractor's licence number and look it up before you hire.
• Anyone has headaches, dizziness or nausea in the house when the garage is in use. Get everyone into fresh air and call for help; that can be carbon monoxide.
• The door is hard to lift or drifts after you add insulation. The springs may need to be rebalanced by a garage door technician. Do not adjust them yourself.
• You find rot, damp or gaps in framing around the door. That is repair work, not sealing.

Getting help in Virginia

Browse more garage door answers, find local pros under garage doors, or describe the job once and licensed local businesses quote it.