Your thoughts on what this might be?

I was asked if I could help by using my IR camera to help determine where insects are coming from in this home. They only appear on the 3rd floor. I came across these two images in different rooms of the 3rd floor and obviously checked them with my moisture meter. Both spots registered 4%. Looked in the attic and didn’t see anything unusual but could only get so far because it was close to the eaves. Any ideas?
1980-01-01 00.00.00-41 1980-01-01 00.00.00-44

Well, what reasons could there be for a spot on the ceiling to be cooler than surrounding areas?
If it’s an attic, perhaps it’s poorly or incorrectly insulated.
Maybe something is in contact with that spot of the ceiling.
Air leakage or ductwork, etc. etc.
Some standard photos would certainly put those images into context.

Did you do an exterior scan for heat loss? And…??

I did not. This wasn’t a home inspection or even an IR inspection. It was a favor for a friend to see if I could help find where the insects in the house are coming from… I hear you though.

My thinking is…
…you have an insect entry problem. The ‘blue’ indicates a moisture concern or cold air leak (you’re in CO in the winter).
Most persons would assume that insects would show as a ‘hot spot’, but that may not be the case depending on temperatures.
A scan from the outside may show an area of heat loss, which to me could indicate the entry point for the insects, thus the cold air leak into the home.
Follow me??


I do. Since there were no insects anywhere but the third floor and I found some dead ones in the atict I figured that is where they were coming from. But you are right I should have been more complete.


Try to remember the 3 basic principles for energy transfer.
1: Conduction. Conduction is the transfer of thermal energy from one object to another through direct contact. Heat transfer by conduction occurs primarily in solids, and to some extent in fluids, as warmer molecules transfer their energy directly to cooler, adjacent ones. For example, you experience conduction when touching a warm mug of coffee or a cold soft drink can.
2: Convection. Convection is the transfer of heat that occurs when molecules move and/or currents circulate between the warm and cool regions of air, gas, or fluid. Convection occurs in both liquids and gases, and involves the mass movement of molecules at different temperatures. For example, [a thundercloud is convection that occurs on a large scale because as masses of warm air rise, cool air sinks.
3: Radiation. Radiation is the transfer of heat energy that occurs by electromagnetic waves, which is similar to light transmission. An example of radiation is feeling the heat of the sun.

Tim, narrate your discovery using the basic 3 principles in energy transfer and the thermogram image you offer.

In my opinion, missing and poorly positioned insulation between the ceiling assembly voids.

Energy loss through Radiation. Poorly positioned insulation between the ceiling assembly voids. Energy loss radiating through the drywall.

Conduction. The corners dark blue bleeding out to light blue would be energy loss through conduction. Drywall in direct contact with the studs.

As to your post. Where insects are coming from.
These could be a different matter all together. Openings in the wall and attic assembly.
1: Trees and bushes touching the wall or roof.
2: Poorly sealed vents.
3: Windows left open or any gaps in the window assembly.
4: Plumbing vents. Poorly arranged or missing water traps.
5: Logs stored in the residence to burn.

Just my take but await other thermographers to chime in.

Bravo! Thanks, very well articulated.

Are the utility lines attached to the area where ants are seen? I had a customer with the same problem only the second floor. Checked the electric line and ants were trailing to the house on it. Followed the line to the utility pole and there they were trailing up the pole.

Hold on there my friend!
Your opinion about missing/improper install of insulation is correct. But this principal is complex and difficult to perceive at times.

Heat transfer through the drywall is through “conduction” not radiation. Radiation travels through space and transparent / translucent materials. Drywall is opaque. It may radiate from the top of the drywall to the cold roof above, where it will be absorbed at the roof deck, but this is a very small amount of the total heat transferred. The primary heat movement is through convention of the attic air against the drywall which is not stopped because of missing / improperly installed insulation.

Energy is radiating “from” not “through” drywall.

Conduction + Convection + Radiation must always = 100%
In this case we have conduction moving heat through drywall from the indoor space (who’s “source” is from a radiant or convective heater). When it reaches the attic side of the drywall, some of the energy will radiate to solid objects in the attic (primarily the roof deck because it is the coldest and largest object). Because attics are ventilated, air convection is always present, which primarily is what removes the heat from the drywall. Conduction is how fast heat moves from the room to the attic through the drywall. Convection may move 90% of the heat from the drywall and the remaining10% will be radiated. 0% is Conducted. Even if there is 0% air movement in the attic heat will cause a natural convection to occur and it is then considered a convection heat transfer.

You must consider at what point of the building system your talking about as all three heat transfers are likely to be involved to some extent from point A to B.

As we analyze things with thermal imaging this is why it is so critical to determine emissivity and temperature reflect in adjusting the camera at any time a temperature tool is used. How many of you know how to measure temperature reflect? And how many actually do it? Temperature reflect is where your “Hot Spot” indicator measures if you elect to put it at the highest temperature point of the object. This is where the heat of the object your scanning, plus radiated energy from other sources in the area (weather hot or cold) are located on the surface of the object. Angle of view effects emissivity as well as improper determination of an objects actual emissivity. How do we determine we have it right? Basic Training!

It’s not just about hot things effecting your target, a clear night sky is in the -75F range. The moon is +720F. When scanning some reflective flat roofs you may find water on the roof freezing when the air temperature is above the freezing point. This is because highly reflective surfaces do no absorb (or emit) energy. Temp Reflect can go either way. This is in reference to the View Effect. Which is why only some of the windows of your car get frosted when others do not on a clear night.

When we discuss the importance of thermal imaging training here, this is the reason. Everything is not as we would normally expect through rationalization.

Q: Does a radiant space heater (without a fan), conduct, convect, or radiate?

Evening, David. I concur. Its harder to explain than my simplistic answer.

I did considered adding both, conduction and radiation, but decided to use radiation hoping someone would chime in to explain.
Heat, ‘energy’, also leaves the house by radiation, through the walls, roof and windows.
I am trying to keep it simple to attract a meaningful discusion.