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Got some cool pics in this attic. [:)]

The two plumes of frost are at the walls of an upstairs bathroom. This bathroom is not being used, no shower curtain so no long showers, no exhaust fan to leak, just a light fixture on the ceiling that is probably leaking some air. An elderly couple only use the downstairs master bathroom.

The insulation between these two frost plumes is wet on top, where you see black on the white fiberglass. Moldy dust, I call that black stuff.

The heat pump was going strong to keep the main floor at 68 F. Up in the bathroom, a register is pumping heat in, and a vaulted ceiling above the downstairs living room is supplying even more heat.

I think they should pull back the insulation and look for leakage at the wall top plates.

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Hello Jim. When the frost or stain is at the baffle openings, yes, it must be coming in from outside through the soffits.

But here, there is frost only in these two places, between the baffles but directly above the interior walls. The one truss is also black. So I think there is a poor seal where the walls meet the trusses. The attic hatch is adjacent and needs some weatherstrip, so some warm air is likely leaking in from there as well.

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The position of the H clips seem too high for the roof panel to reach down to the eaves. Maybe there's a horizontal seam in the decking just below the top of the baffles, out of site, that provides the little extra cooling needed to put conditions barely within range to make ice.

Marc

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I see it all the time.

My theory:

Cold day.

Heat loss through walls.

Air film next to walls gets warm and rises.

Rising air gets sucked up onto the soffit vents and condenses on the cold sheathing surface.

A little sunshine does the same thing. IIRC Dr Joe measured air film temps as much as 20 degrees higher than ambient.

Add some more baffles and blow in 8-10 inches of cellulose. That should be dense enough to seal things up. Blown glass is almost useless as insulation.

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More info? Sure. It was a frigid day, about 2 degrees below freezing with a skiff of snow.

There is plenty of soffit ventilation as seen by the baffles, a poly vapor barrier and about 14" of insulation. The upstairs bathroom was quite warm due to a wide open register and like I said, the thermostat down in the living room with a double height vaulted ceiling. There is minimal staining anywhere else, 12 yr old house.

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There is no humidifier, don't need them here. The air is either moist or frozen.

The plumbing vent comes up behind the sink in the right interior wall, then crosses over to the roof jack above the left, suspended by the strap in pic3. Yes, warm air could be leaking out around the hole in the wall plate or the pipe itself.

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Got some cool pics in this attic. [:)]

The two plumes of frost are at the walls of an upstairs bathroom. This bathroom is not being used, no shower curtain so no long showers, no exhaust fan to leak, just a light fixture on the ceiling that is probably leaking some air. An elderly couple only use the downstairs master bathroom.

The insulation between these two frost plumes is wet on top, where you see black on the white fiberglass. Moldy dust, I call that black stuff.

The heat pump was going strong to keep the main floor at 68 F. Up in the bathroom, a register is pumping heat in, and a vaulted ceiling above the downstairs living room is supplying even more heat.

I think they should pull back the insulation and look for leakage at the wall top plates.

013126214656_AttcFrost2.jpg[/img]

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I think you nailed it.

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How many people live in the home, do they use exhaust fans, how tight is the home, what was the outdoor temp prior to your visit,what's the humidity in the home, so there are baffles - is there daylight from the soffit vents? This is the kind of stuff I consider.

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