Can Attic Fans Help Prevent Ice Dams?

If heat doesn’t build up in your attic, you probably won’t have any ice dams.  One way to help prevent heat build-up – and therefore ice dams – is to have a well-insulated, well-ventilated attic.  That works.

(Why?  Quick refresher: Ice dams start off as snow.  Hot air from inside your house rises into your attic, causing the bottom layer of snow on your roof to melt into water.  The water flows down your roof until it meets a cold spot – usually your eaves.  Your eaves are the coldest part of your roof, because they aren’t heated from underneath by the living space.   As the snow melts and travels over your eaves, it becomes a “dam” of ice.  Water pools up behind the ice dam and then freezes, resulting in an even bigger ice dam.)

But can’t you also prevent overheating in your attic by pushing the hot air out with a fan?  Won’t the fan just blow the hot air out through your roof vents?

No and yes.

Although setting up fans in your attic will expel hot air, they won’t help you prevent ice dams.

The whole reason your attic is hot in the first place is that there are leaks or poor insulation between your attic and your living space.  If you push hot air out of your attic, more hot air from inside your home will just rush in and take its place.  All you’re doing is making the heat escape faster from your cozy rooms.  You’re cooling your living space and heating your attic – precisely the opposite of what you’re trying to do.

In fact, you may even make your ice dam problem worse, because you’re constantly feeding your attic a fresh supply of hot air with which to heat your shingles.

To add insult to injury, your heating bills will rise (just like the hot air that’s being wasted in the attic).

That’s why attic fans are a non-starter for ice dam prevention.

Simply insulating your attic will keep your home warmer and your attic cooler. In addition, seal all the places that warm air can escape into the attic, like areas with wires and plumbing, lighting fixtures, heating fixtures, chimneys, etc.

If additional insulation and sealing attic bypasses are not on your list of priorities this year, then the easiest and most cost-effective way to prevent ice dams is to keep your roof as snow-free as possible.  (And if it’s too late for that, just call an experienced and insured ice dam removal pro.)