"Stormin Mormon" wrote:

Does it work for finding cold leaks into the house, or heat leaks out
of the house? I mean, can you point it at the edges of the door or
window or pipe and get a temp reading off of air that is blowing in or
out, or do only solid things radiate IR?

Gases don't radiate, generally, but you might sense lower-temp wood trim.
Or feel around the door with your hands on a cold day, with a large window
exhaust fan running. You can find which rooms have the largest air leaks
and measure airsealing progress with a $70 Kestrel 1000 wind velocity meter
in another partially open window. When you open a door to a leaky room,
the air velocity will decrease. As you airseal, it will increase.

Richard J Kinch wrote:

Point it up at the zenith of a clear, dark sky on a warm night. Brrr!

Inexpensive IR thermometers ignore water vapor (so people can use them in
boiler rooms full of steam), so this might also work on a warm summer day.

Nick