Kitchen Island Hood problem

Hello,

Not sure if I chose the right category to ask this question. I apologize if it’s misplaced.

I installed a kitchen island hood last summer with 6" exhaust duct straight up through the ceiling into the attic and through the roof in a bangalow. Location - Toronto Canada. I assume it's a zone 6. The duct was inside insulated sleeve.
Now that the winter is here and temperature changes sometimes 10 degrees in one day occasionally water is leaking from out of the hood.

My assumption is that warm air that is being exhausted on a very cold day is freezing somewhere inside the duct or at exit point inside the roof hood and then melts when it gets warmer and drips down the duct onto a stove under the hood. At times amounts of water are quite large.

Has anyone encountered a problem like that? What can be done to stop this leak or should have been done differently?

Thank you,

Andrei

Asked by Andrei Sosnovsky
Posted Wed, 01/25/2012 - 18:41

Tags: GBA Pro help

1.

Andrei,
Ideally, your duct would have a 90 degree elbow in the attic, so that the duct would terminate at a gable wall. (If you have a hipped roof, that obviously isn't possible.) The idea is to install the elbow at a height that allows the duct to slope from the elbow toward the gable termination; that way any condensation can drip to the exterior.

If you can't re-route your ductwork, I would check the damper on your duct to be sure it isn't stuck open. You could also increase the amount of insulation around the ductwork in the attic; that might raise the temperature of the duct enough to make a difference.

Answered by Martin Holladay, GBA Advisor
Posted Thu, 01/26/2012 - 09:06

Edited Thu, 01/26/2012 - 09:07.

2.

Yes, it is a hipped roof, so adding sloped elbow is not possible. Damper is working fine.

Thank you for the answer Martin.

Answered by Andrei Sosnovsky
Posted Thu, 01/26/2012 - 20:03