Thought I would share this with those folks who perform thermography services with home inspections, especially our up-and-comers like Paul and Frank. I can never tell if the answer is going to be obvious to everyone, so I apologize if this turns out to be a no-brainer for you.
Here are two recent examples of air leakage at interior walls of new construction homes (blower door tested homes).
Both examples are interior 1st floor walls (no exterior exposure on either side) of 2 story homes. The houses are under slight negative pressure. Interior temperature has been stable for some time so we should be near thermal equilibrium. Pretty narrow temperature span on the images
In the first example outside is cool, interior is warm. Air leakage through switch boxes installed in the sheetrock.
In the second example outside is warm, interior is cool. This is a laundry room which backs up to staircase with the under-stair area fully sheetrock enclosed (no access). The first image shows the location of the studs as cool compared to the sheetrock (would you expect this on an interior wall?), the second image shows air leakage around a metal clean out cover for the washer drain.
Where might the air leakage be coming from? What would you look for? I have photos of the answers which I’ll share. Do we care about the air leakage when the temperature difference is so small?