How to Find Cold Spots and Air Leaks in Your House

On a cold or windy day, close all windows and doors, turn on the bathroom and kitchen exhaust fans to depressurize the house, then move a wet hand or a smoking incense stick slowly around window frames, door edges, outlets, baseboards and attic hatches. Movement in the smoke means a leak.

A $30 point-and-shoot thermometer shows cold spots along exterior walls, headers and rim joists when it is cold outside. It is spot-reading only, so scan slowly in a grid pattern.

Phone-attachment thermal cameras have collapsed in price and show missing insulation, wet insulation and air leaks as clear plumes. Best used with a 15°F or greater difference between inside and outside temperature.

Dirty, dark-stained insulation is filtering air. Check around plumbing stacks, wiring penetrations, dropped soffits and the rim joist. Daylight visible at the eaves or hatch is a leak you can point at. An uninsulated attic hatch is one of the biggest single holes in the ceiling; the attic hatch insulation calculator sizes the foam layers and the dam around it.

A professional energy audit pressurizes the house with a calibrated fan and reports air changes per hour. It costs $200–$600, is often free or discounted through utility programs, and is the only method that gives you a before-and-after number.

Found the leaks? Seal them with our air sealing product picks. Drafty garage door? See the best garage door insulation kits.