Coalpail.com Forum

Subject pretty much says it all. I've seen minor frost in my attic before but this year (first year with the coal stove in the basement) it seems like the frost is much worse than usual (see images). I read an article saying that a negative basement pressure can result in frost in the attic. I'm essentially using an open basement door as a cold air return and I can feel a TON of air coming down that basement door. I suppose if that much air is coming down the basement door that an equal amount of air must be escaping through the attic?

House is built in 95, really tight. Has 12 inches of fiberglass insulation in attic....

Anyone have any suggestions on what might be happening here? Would a cold air return from the second floor help?

Is your attic vented well ? Air from your house should not be getting into your attic, also vapor barrier should be installed.. as far as negative basement pressure, never heard of that..

Crack a window in the basement.

As I thought, your getting air in the attic from your house, you need to find out where its coming from and seal it off..

https://structuretech1.com/frost-in-attics-2/

Need to air seal, and improve attic venting.

Brandon,
2 things:
1- If you have ridge vent and soffets, they make a shield to keep that 12" fiberglass insulation from blocking the soffet vent.
2- If you have a concrete block, lined chimney, it's a good idea to block the gap between the cinder block and the floor joists in the basement, stopping the heat to escape to the attic.
Cheers

Rob R. wrote: ↑

Sun. Dec. 31, 2017 7:22 pm

Need to air seal, and improve attic venting.

yup! cold meets warm...condensation=ice, frost etc.

coaledsweat wrote: ↑

Sun. Dec. 31, 2017 7:05 pm

Crack a window in the basement.

Wouldn't that make it worse? It would increase pressure at the ceiling of the top floor.

Lightning wrote: ↑

Sun. Dec. 31, 2017 7:50 pm

Wouldn't that make it worse? It would increase pressure at the ceiling of the top floor.

Yes..

Just checked my attic, roof nails have no frost. Garage is in the 50/60's with attic stairway covered with 2 inches of foam. Rest of the attic has about 8 inches of fiberglass, with styrofoam vents channeling soffit air into the attic. House is a ranch and main floor is running at 68 to 70. basment family room with stove is in the low 70's, outside is 2.
I would suspect you need more attic ventilation, or have heated house air leaking.

Frost is forming because the outside of the roof is cold...
Warmth from home is moving to attic...
Warm air holds more moisture...
Inside surface of roof is the meeting point...
Frost is result...
A house built in '95 is not 'really tight' just tighter than previous building standards...
Frost in attic is proof of that...
Energy audit with blower door test will find the cause...
The heat from the basement is pooling on the second floor and causing more heat in the attic...
Look for the obvious holes to the attic and foam them...
Bath vent goes outside right?...
How is the attic vented?...
Gable vent or roof vents...

Anyway to block off or at least slow down hot air movement up to 2nd floor. It is probably warmer up there than it really needs to be anyways.

And if it were not so cold now you would have some wet condensation in there instead of frost.

As for adding return ducts from second floor it would help to get nearer to having a balanced duct system which makes temps and moisture levels more even all around.

Lightning wrote: ↑

Sun. Dec. 31, 2017 7:50 pm

Wouldn't that make it worse? It would increase pressure at the ceiling of the top floor.

The frost isn't from pressure, it's from a constant influx of fresh, moisture laden air.

New roof was installed this summer with all new ridge vents installed. The roofer even added a vent to the porch. The bathroom vent used to vent into the attic and I had him cut a hole to have it routed out.

The second floor in my house is not that warm. Basement is around 75-77, first floor keeps steady at 70 (coal trol is on the first floor controlling this) and the second floor can get as low as 60 but is usually around 63.

Someone mentioned it (and I think they are right) and that is that a energy audit is in order. I need to figure out how moisture is getting to the attic. I don't see anything obvious.

Thanks for all your replies. Any recommendation on someone who does energy audits?

Brandon, is there soffit vents and is the insulation covering them? For the ridge vent to work well both summer and winter you need soffit vents.

As a side note they have products designed to fit into the corner. It's folded and you staple the bottom fold to the sill plate and the top fold to rafter. This leaves a gap for the air from the vents and you can but the insulation up against it. It's supposed to help with ice dams too.