What's happening here?

[kweiss]

Yesterday's townhome warranty inspection. 55 degrees and cloudy outside and 73 degrees inside, furnace running.

See the two IR pics of the ceiling to the attic. Note the clearly defined slightly colder areas. There were several of these in the main living area. Not going to report anything about these, but I am curious as to what is causing them.

Initially, due to the small temperature difference, I though maybe these areas would be under the attic decking for the HVAC access. That there might be missing or improperly installed batt type insulation under the decking. When I got into the attic, I found that there is no decking in these areas. The access was poor but I could see that there was blown certainteed type fiberglass insulation above this room. The insulation install was typical and adequate. Being blown in type insulation, there was variance in the level through out. No clearly define rectangle with less insulation were visible from the attic.

So what is causing the colder rectangles. Not something I normally see and I am curious.

[John E. Mullarkey]

My guess would be that the isulation was somehow compressed. Is this an older house that had the insulation upgraded? new insulation shot over existing typical batts that might have been compressed?

Just a thought

[Wayne B. Wilson]

With that little of difference , I wonder if it is compression , Or is it a different type of insulation . Any pictures from the attic?
Was the main duct in that area?

[Jason Kaylor]

yeah I agree, it is compressed or a different type of insulation. It could also have been compromised in some fashion, but because of the exact shape I doubt that is the case.

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[ldapkus]

Convection Colder air moving behind the vapor barrier. See it quite a bit.

[kweiss]

One year old construction. Blown in fiberglass insulation. Did not take any pictures of the attic because they would not show anything. Typical new installation for around here, variable surface levels between 10 - 12 inches as is typical for that type blown in.

Compression?

NO signs of compression or disturbance at all in the insulation. Certainly nothing in a recognizable shape as indicated in the IR pic. While the area was not easily accessible, I could see the area above the pictured anomaly reasonably well.

Vapor Barrier?

I do not typically see a vapor barrier under the blown in insulation around here. Notice these areas were not along an outside wall, they were in the middle areas of the room.

Possible something laying on the sheetrock in that channel between the ceiling joists? Could not get close enough to dig in it.

[Wayne B. Wilson]

OK
here is a thought i wonder if something was left and insulated over. Like bags from the insulation.

[Jeffrey Moore]

What was the temp in attic? If the attic was warmer than outside air the ceiling Delta is not as great as a wall. This could account for the smaller temp diff between the areas.

[measter]

Originally Posted by kweiss

Possible something laying on the sheetrock in that channel between the ceiling joists? Could not get close enough to dig in it.

Yes. That what I would guess. Looks like an air gap due to it being pretty consistent across the rafter spaces.