exhaust fans and ice dams

[J Kelly]

Last winter after a heavy snow I had a couple of problems with ice dams. One above the exhaust hood over the stove, another above the bathroom. Both appear to be caused by improper installation of the fans, they both vent into the attic space. I'm going to correct this by having them vent through the roof.

My question is this, wont the warm air coming out of those vents melt the snow on the roof, and wont the resulting water end up freezing into an ice dam as it tries to run down the cold roof where it runs into more snow?

[No]

Yes and yes - Better to vent through the soffit or a gable end wall.

Then - Make sure your attic is insulated and well vented. Soffit vents not blocked, gable or ridge vents as well.

I would love to someday use remote blowers for my kitchen and bath ventilation needs. Something to consider as well.

[Joseph Meehan]

Yes, that is a classic case of irresponsible workmanship.

[J Kelly]

I think you misunderstood what I meant, rereading what I wrote I see I wasn't very clear. After I correct the incorrect venting by installing roof caps and running both exhaust fans to said roof caps, won't the heat coming out of them when the fans are on cause the same snow melting and ice dams that I get now by just leaving the vents in the attic? Or will it just melt a little snow around the vent and then the heat is able to escape before causing more melting? I'm in northern Iowa, we can get some big snows.

[barry]

Warm air will go up, up, and away rapidly. Do make sure the attic is properly insulated below, and vented, as others point out. That may have contributed to your initial problem- one clue would be a fungus colony in the rafters.

J

[J Kelly]

I do have another venting problem, some a-hole stuffed the soffits with insulation, and only installed two vents on the roof when it needs at least 4. Hope to find someone to fix that stuff as well. I hate attics..

[Joseph Meehan]

This is normally not a problem. You may want to put insulation around the venting. I suggest solid metal, not flexible plastic.

[jstp]

Here's an interesting site concerning ice dams, lots of examples.

If you are concerned that the warm air from the vents will melt the snow, investigate insulated vents and/or higher stacks.

[J Kelly]

Thanks for the replies. I have my plumber lined up to fix the vents later this week. I don't want to cut the hole in my roof myself, and I hate attics!