Preventing Ice Dams on Your Roof

Find out how to avoid water damage from melting ice dams on your roof this winter. Preventing ice dams from forming on your roof is often a matter of combining insulation and passive ventilation solutions.

[mai_avatar size="40" margin_right="-4px"][post_author_posts_link before=" by "][post_date before=" — "][mai_icon icon="comment-alt-lines" style="light" display="inline-block" size="1em" margin_left="12px" margin_right="-8px" margin_bottom="-4px"][post_comments][post_sponsor][shared_counts]

LESLIE: Herb in Michigan needs some help up in the attic. What can we do for you?

HERB: So I’m having a problem with ice dams. I’ve had it for quite a few years. On the side of my house where it’s a hip roof and – there are vents there and I’ve put extra insulation in but where the hip meets up with a room and it goes through the rafters, I get the ice melting there and then I get all the ice on the edge of the roof.

TOM: Well, the problem is that you’re allowing – there’s warm air that’s getting up into that space and as the warm air gets up there, it’s going to melt the snow which is on the roof right above where the air escapes. That water runs down to the roof edge and because the roof edge is overhanging the exterior wall, it freezes; hence, creates a dam. And eventually, that water can back in and cause leakage.

Now, a couple of things you do to prevent this. First of all, to stop the leaks, you use something called ice-and-water shield but that’s best done, obviously, when you’re installing a new roof. Because your roof is already in, we want to try to do everything possible to reduce the amount of warm air that’s getting up there.

I would suggest that you increase your insulation and, secondly, you make sure that you have good soffit ventilation and ridge ventilation so that you’re letting cool air get in at the base of the roof, run up in between the roof rafters and exit at the ridge. If you have proper attic ventilation and excellent insulation, that will do – go a long way towards preventing those ice dams from forming, Herb.

HERB: OK. Is it possible to do a power vent to pull it out faster or won’t that make any difference?

TOM: (overlapping voices) No, no. If you put it – first of all, putting in a ventilation fan is a bad idea, especially even in the summer because it will actually suck conditioned air – air conditioning out at your house. It wouldn’t work because they’re on a thermostat-type switch, so that wouldn’t come on. So using a power ventilator is not nearly as effective as passive ventilation when you have a system of continuous ridge and soffit vents. A hip roof is definitely a little bit trickier to vent but it will work if you have good, open ventilation.