what am I seeing?

I have seen this twice now, coarsely chopped fiberglass and random cold spots on the ceiling (cathedral ceiling with scissors trusses, 12 inches insulation depth no access)
I think cold air is moving down through loosely packed insulation and getting to the ceiling, but a colleague disagrees, and says insulation has settled and is compressed at the cold spots.
Any other opinions?

I agree with Eric no way can insulation even if there is some compression at the bottom the balance would still do a fare job.
Adding some cellulose blown in might help to fill the air gaps in the existing insulation.
Another idea is a small fan constantly running might stop the cold spots from forming .

Could be air pockets due to the course insulation or rodents but I don’t see any trails in the photo.

What brand/model camera is this taken with?..


Has there been any mudding /drywall repairs done recently?

My thoughts exactly, that’s bad…

Your asking questions about a image that does not appear to have been thermally tuned and almost impossible to tell what is going on with your image. It would just be a WAG

Testo 875-1

Teach me for getting fancy with the software, like these better? Outdoor temp was pretty warm that day, if it was colder the blobs would have better definition.





Then that would lead us to hypothesize that it could be air?

When I am in the software I tweek the yellows a bit darker and the blues a little softer. Its just a fine line to provide a sharper image especially on your bottom image. Every thing is adjustable except the focus

In the three images all I see is a little air migration and some thermal bridging at the end of the studs. Seen it a million times nothing to write home about.

You will learn to control mother nature I care less what the outside ambient is I have a A/C unit and a furnace to provide what ever temp I want inside. I can make a delta T given enough time;-)

You will learn to operate you camera to have a good thermgram.
I was the same eric.

Hold you camera’s lens at a 90% degree angle to the object you are shooting.
That will get you the best and most direct FOV posable.
You must also adjust your level and span.
In the office utilize the palettes in the software.
It takes time Erick.
Is that the 875-1 or the 875-1i
9 Hz or 33Hz?

Not enough temperature differance for water.

The entire span of your image is 2C°. The difference that you are seeing is about 1C°. If I had to hazard a guess based on the color renderings, I would suspect that the insulation is not making full contact with the air barrier (sheetrock). Possibly, mouse burrows, looks like there are trails on the top side…

I personally would not consider such a small anomaly to be report worthy in a home inspection, but that’s just me. I wonder what the ROI break even point would be for attempting to “correct” it?

You would want to have a known minimal temperature differential across the thermal envelope and time enough to reach equilibrium.

I have no idea why screen refresh rate would be considered a relevant question to assess a still image???

This was from this morning before noon, when one can see the nail heads in the dry wall you know the delta T is as good as it ever gets inside a structure. It was about 65 degrees inside no heat on when I arrived it did not take long to warm up the inside warmer than what the attic was. This is the time of the year when one does not have to manipulate the temps very much

The heat transfer rate is a multiplier of the temp differential. Less than 2 degrees as well as the small area ratio is insignificant.

Conduction losses are also much less of an issue compared to convective loss (and even radiation transfer), but conduction loss is all that is talked about (insulation and windows)…

I wouldn’t try to fix that even if it were my own home.

Thanks all, as I said I have only seen these blobbies a few times, first time was a client who asked me to check his house because there were cold rooms, this last the client also complained about the heat until they added a pellet stove. I was there because they had a problem. 99% of the time I see the same as in Charlie’s example, the joists or trusses. I have also seen obvious cold areas and found that was where insulation was missing in the attic. Here are some more, from April, outside temp was -9 C or about 15 F, cold rooms in house, I was able to enter the attic, and could not see any missing insulation.


In your first and third images you can see where the truss supports enter the insulation and then compare the thermal to the digital and you can see where the temp follows the brace into the insulation. The whispy areas in the insulation are simply temp intrusion thru the insulation. Needed more insulation

From last week.
Rear ceiling.
90 pound saturated felt with granular.
2" lap with exposed nails.

Good explanation! Conduction!

Conduction occurs when two objects at different temperatures are in contact with each other. You know, like when you wake up in the middle of the night because your companion is cold, so you get the great idea! Mr. Johnson and thermal equilibrium…No, no, no, no… not the best example.
Lets move on.

Heat always flows from the warmer to the cooler object until they are both at the same temperature. Thermal Equilibrium.:smiley:

The heat is conducted through , in this case, wooden truss members. Thermal conductivity and temperature transfer. Its always goes in one direction.