Condesation - Contractor Talk - Professional Construction and Remodeling Forum

big builder · 11-23-2008, 04:51 PM

Hello everyone,

I have this bad problem with condensation in my personal house.

I made the mistake of spray foaming almost the entire roof. It's a complicated design and I have struggled with condesation in the attic and some wall sections.

I should have just gone with complete plastic vapour barrier.

I have just installed three powered gable fans to try and help suck out the air .

I can see brown water running down my soffits and fascia now.

My question is this: I am thinkg of running my HRV non-stop to try and
get rid of the moist air inside..... will think help and realistically how much will it increase my heating costs?

The house is over 5000 sq ft so it's not a few cents.

Does anyone have any other ideas for aleviating this problem?

Thanks for any advice.

delta l · 11-23-2008, 05:35 PM

Quote:

Originally Posted by big builder

Hello everyone,

I have this bad problem with condensation in my personal house.

I made the mistake of spray foaming almost the entire roof. It's a complicated design and I have struggled with condesation in the attic and some wall sections.

I should have just gone with complete plastic vapour barrier.

I have just installed three powered gable fans to try and help suck out the air .

I can see brown water running down my soffits and fascia now.

My question is this: I am thinkg of running my HRV non-stop to try and
get rid of the moist air inside..... will think help and realistically how much will it increase my heating costs?

The house is over 5000 sq ft so it's not a few cents.

Does anyone have any other ideas for aleviating this problem?

Thanks for any advice.

Where are the fans pulling air from? Is the attic vented? Assuming that you're now in heating season, are the fans controlled with simple on/off switches? What is your location?

Delta

big builder · 11-23-2008, 08:21 PM

The fans are mounted in the gable ends. They will pull air form the attic area. The roof is such that half ( or more) is cathedral and spray foamed and the rest is attic. I have the fans mounted to on/off switches and plan to run them non stop..........maybe forever.

We are in central ontario.

The attic has continuous ridge vent and rafter vents in every cavity as well as continous vented soffit.

It's just not working.

The sadest part is I build all day and this has never happened to a customers house.

It's driving me crazy

cleveman · 11-23-2008, 11:58 PM

if you spray foamed the roof, I don't understand why you have roof vents. Shouldn't you be ventilating the cold side of your roof? And since you have cathedral ceilings, isn't the cool side of your roof the exterior?

big builder · 11-24-2008, 06:39 AM

The design of this roof is such that about 2/3 the length of the roof rafter is cathedral ( spray foamed) and under that spray foam is rafter vents stapled to the underside of the roof sheeting. This allows air to move from the soffits into the attic area ( the other 1/3 of rafter length) This attic area has blown in insulation.

If I had spray foamed the entire roof area then I would not have used ventilation. Although I am not a believer in spray foam as a vapour barrier any more.