Should You Cover Your AC Unit in Winter? What Makers Say

Know what a wrap traps

Moisture. Lennox says air conditioners are designed to run in open air, and a cover that restricts the airflow lets moisture build up. That leads to rust and corrosion, and damp that can harm the electronics.

Mold and pests. Lennox says the lack of airflow can invite mold and mildew, and a covered unit attracts rodents and small animals escaping the cold.

Frozen coils. Lennox says moisture under a cover can leave it colder under there than outside, and possibly freeze the coils.

The warranty. Lennox says that depending on the maker, covering the unit may void its warranty.

Cover only the top, and only if you need to

Heavy snow and ice. Trane says that in an area with lots of snow and ice, you should consider a cover. It must be breathable, like its WeatherGuard top cover, and never airtight or watertight.

Trees overhead. Lennox lists falling debris and leaves from nearby trees, and advice from your technician, as the reasons to protect the unit.

How Lennox would do it. A board such as plywood secured on top to stop falling debris and reduce ice buildup, a shade or an extended awning, or a lightweight breathable cover. Whatever it is, keep the airflow above the unit open.

The maker’s own top. Lennox says some makers offer custom fitted tops. Trane’s WeatherGuard comes in two kit sizes, for bases of 33 by 30 inches and 37 by 34 inches.

Clean it first. Lennox says to inspect the unit and clear the debris out of it before any cover goes on.

Keep the snow off

Why it matters. Trane’s owner’s guide says the outdoor unit depends on air flowing freely over its coil. Anything that blocks it makes the compressor work harder, and snow and ice buildup restricts it.

Clear it. Trane says to clear snow from the area around the outdoor unit as soon as you can after it builds up, and from the top and sides of a heat pump.

Ice and noise. Trane says that after freezing rain, if you notice a lot of ice and noise, call an HVAC professional: a heat pump frozen in winter.

The WeatherGuard. Trane says its breathable top can stay on all year: it keeps pollen and debris out in spring and summer, and leaves out in the fall and winter.

Protect it the simple way

Keep the space around it clear. Trane’s owner’s guide says not to plant flowers or shrubs right next to the unit, and not to stack anything against it or drape anything over it.

Clean it and service it. Lennox’s alternatives are regular professional maintenance, cleaning and inspecting the unit, and changing filters on schedule: how to clean the outdoor unit.

Get the heating ready. Trane’s first winter tip is a furnace or heat pump tune-up, and changing the filters more often while the heating runs longer: how often to service it.