frost in attic

bakmorse

I will try to keep this as short as possible. Last January I went into my attic(not finished two story house) and I found dripping water and black mold all over my roof and soaking wet insulation. I called a mold remediation company to take care of that problem and I thought i fixed the moisture problem. Here is what i did, my soffit vents were non existent (blocked off by insulation, so i pulled insulation back, removed wet insulation, added 18 inches of roll insulation (now have 23 inches) (I dont think there was a vapor barrier beneath the old insulation), added ridge vent, added attic fan with thermostat and humidistat, recently put thermometer and hygrometer up there only to find the humidity level to be 85%, house RH @ 33% outside temp 21 attic temp 30 Just looked up there and i have frost on the roof again, and some slightly moist spots on my insulation. I'm wondering after reading other posts if the gable fan and vent are counter productive and negating the soffit and ridge vents. Now I am clueless. What else can i do?

Slyfox

Once you verify that you have proper ventilation and insulation,


inspect your roof to make sure it's not leaking.
Even a minor leak that is being hidden because the leak is low on the roof and leaking into your eave overhangs or in a valley in which may at times be hidden by additional structure boards, could still allow moisture into the attic and cause issues.

Once the above is found not to be an issue, you want to check all ceiling penetrations such as plumbing stacks, in set lighting, sky light fixtures, duct work, etc.
Anything penetrating the ceiling should be properly sealed so to not allow warmer air from the living space into the attic space.
Also make sure your bathroom & kitchen exhaust fans are not venting into the attic, they should be vented directly out of the home, via the roof, eaves or walls.

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MJW

You are on the right track.

bakmorse

Thanks for the replys. I dont have any vents going into attic, I do have the furnace vent going through will check that for leaks. I have a whole house fan (have it sealed off) I was wondering if I should block off the west end gable vent and the east end attic fan? Thanks again for any help.

oh'mike

Make sure that the soffit vents are open and not blocked by insulation--You should be able to see light coming in at the soffits--

bakmorse

just blocked off gable vents and fan. there's plenty of light coming through soffits. just a waiting game now to see if humidity falls over the next couple of days. Thanks again.

oh'mike

Gable vents are famous for being under sized---Consider adding a ridge vent in the spring--and then blocking the gable vents so convection will pull from the soffits.

bakmorse

I have continuous ridge vent now, i think the gable fan and vent were screwing up the flow from soffit to ridge. Thanks Mike.

mjdonovan

It sounds like you did all the right things in terms of fixing the attic ventilation and insulation. However, I'd go back and make sure your bathroom exhaust fans are being vented outside and not into your attic.

Also, make sure there is insulation tucked well around any vent stacks that may be coming up from the living area below. The holes associated with vent stacks can let a lot of warm moist air into the attic.

Finally, check the roof for leaks. I suspect you don't have a roof leak as you would probably see water coming down into the living area of your home, or at least forming wet spots on the drywall ceilings.

OldNBroken

Bakmorse, it sounds like you did your homework and you did the next thing I would have recommended. I'm guessing your gable vents were short-circuiting your ventilation.

Let us know how it turns out.

bakmorse

well, it has been 28 hours since sealing off gables, and wraping the furnace exaust stack elbows (didn't seem to be leaking but figured why not) dont see any leaks in roof, no other exaust coming into attic. Hygrometer reads 88% not looking good for the home team.

Jackofall1

You mentioned that you had a whole house ventilation fan, how well is that sealed off, sounds like the biggest opportunity.

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bakmorse

sealed it off in the interior with a whole house fan cover, sealed it off in the attic with 1 inch insulated sheathing. and wrapped all edges with shurtape ductwork tape. Thanks

OldNBroken

meter broken?
sorry, just had to throw that in.

I just noticed something you never mentioned. Do you have a barometer? Are you still getting the dripping condensation you were experiencing before?

MJW

I think you may want to add some bath fans and a fan in the kitchen. With no fans to move moisture out and no vapor barrier, the attic is getting a ton of moisture pumped into it.

What is the situation with the roof? One layer? Two? I&W shield? how much? Is it shingles or tin?
Is the attic fan coming on? Doesn't that seem to help?