If you have recently hired a contractor to install an air-source heat pump at your house, you probably have a so-called “indoor unit” on an indoor wall, as well as an “outdoor unit” on a ground-mounted pad or a wall bracket. You might be wondering, “Should the outdoor unit be protected by a small roof?”

If you ask your contractor this question, he or she will usually answer, “Don’t worry—you don’t need a roof. Those outdoor units are designed to be weatherproof.” Although that statement is technically correct, it doesn’t tell the whole story.

Some units will benefit from a roof

It’s true that heat pump manufacturers do not require their outdoor units to be protected by a roof. That said, you may want to install a small roof over your outdoor unit to protect it from the rain. After all, keeping rain off the unit may reduce the chance of rust and extend the unit’s useful life.

If you live in a snowy climate, you’ll probably want to install a roof to reduce snow accumulation near the unit. If your outdoor unit ever gets buried in snow, the reduced air flow through the unit will prevent your heat pump from operating properly, and the heat pump may shut down completely.

Several factors will affect your decision on whether your unit will need to be protected from snow: