Here’s a good one for you.
What would be causing the dark marks under each truss on the finish side of the sheet rock? Just on the outside walls. I have cellulose insulation sprayed in the attic. I don’t have my soffits in yet but they are will vented. No insulation tuching the roof. and only have one gable end vent in due to the wind. Could it be I need more venting? Is it cheep paint? The house is in Valdez Alaska. Lot’s of temperature differences. Also my insulation has settled down to a foot in places. I took a rake and tried to get to puff up some. Should I think about spraying more in.
Replies
I've heard of candle smoke settling on the ceiling along framing members. The lumber is a hair colder, so moisture condenses there. And dust/smoke attaches itself to the moisture.
If the house is under construction, it could be about anything. Your concrete is probably still giving off moisture.
Coule be the problem will go away once the house is finished.
With no soffit yet in place, it is easier to imagine that the wood members ( bottom chord of truss) are conducting cold in from outer edge. OK - technically, they are conducting heat away from the interior faster than it leaves through the cieling insulation.
Result is that the cieling right there is cooler than other parts and condensate is happening.
It can be smoky condensate adding soot in those locations like Boss mentioned. Happens to show up faster when occupants burn wood, smoke cigarettes, or burn candles.
Or it can be normal water vapour comndensing there. That will collect dust on the damp surface faster than other spaces and that dust, combined with the moisture, will encourage growth of mildew, which shows as a dark stain.
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My vapor bearer is really tight through out the hole house. I hope that its not mildew.
No smokers, fire places or candles here. I don't have my HRV hooked up yet. Should I add more Insulation now that the older stuff has settled to just a foot thick?
Really tight vb and insulation but no recovery system yet - there is your problem. Tight places like that in the far north are getting a lot of press for mold problems when the total suystem is not working together.
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Thank's. Guess I had better get the HRV. Have any ideas on what brand I should buy? The House is about 2900 sq feet.
I don't know specific brands - I go with advise from trusted installers who are the ones that get stuck with servicing them
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Tanks for your help. I think I am leaning toward a life breath
There is a temperature difference near the trusses, compared to the rest of the ceiling. In your situation the area under the trusses is probably colder than elsewhere, and this causes soot from candle, cigarette, or fireplace smoke to accumulate in bands under the trusses.
It can also happen due to electrostatic charge (and, in fact there may be some electrostatic effect with the trusses). "Charge up" a balloon in winter by rubbing it against a wool sweater and stick it to the wall. If there is any smoke in the air, a dark "halo" will accumulate behind the balloon.
that latter sounds like a future electric vehicle from the fifties, "The Electrostickmatic"
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Can't this be prevented by furring down the trusses prior to hanging the drywall? So the dry wall hangs on the furring?
and or by stopping the thermal bridge with a foam panel under the cieling joists.
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My outside walls are foam panels. Could this have anything to do with what is going on?