Under the right conditions, thermal images clearly show insulation problems. Shown here are partially filled wall cavities typical of poorly installed loose-fill cellulose.
Uninsulated exterior walls, which the homeowner knew about, and an area of missing fiberglass batts in the ceiling that he did not know about.
A hit-or-miss cellulose job — a problem that has become less common thanks to dense-pack equipment and improved blowing techniques.
Voids in the insulation are clearly visible in the band-joist area of this two-story home. The characteristic "bull's eyes" on the window glazing are an early indication that the inert gas fill has become depleted, allowing the double panes to squeeze together near the center. IR can readily detect this problem — which is otherwise difficult to spot — and enable a builder or homeowner to make a claim with the manufacturer before the expiration of the window warranty.
Depressurizing a structure with a blower door reveals characteristic "fingers" of infiltrating outside air, as can be seen underneath this baseboard.
Infiltration paths aren't always so straightforward: In this image, cool air — probably drawn up from the basement — flows from one intersection of a wall and ceiling, while warm air infiltrating from the attic is visible a few feet away.