One of the cool tools that I use during inspections is a FLIR Thermal Imaging camera. This allows me to take measurements of temperature differentials of various surfaces and objects during an inspection. Useful for finding areas of air leakage and hidden insulation problems.
I took a picture of my sleeping dog Magoo this morning to show what the camera is capable of doing. The image on the left is the regular digital camera image while the picture on the left is a blended thermal image. Relative cool areas are darker, warmer areas are brighter. Magoo is working hard at sleeping and is significantly warmer than the floor he is laying on.
Thermal imaging works best when there is a large temperature differential between the inside and outside of the house. The images above show a front door from the inside on a cold morning. You can see a big temperature drop at the bottom of the sidelight window on the left and the bottom of the door. Looks like there is some air leakage on the bottom of the door - the weather stripping likely needs to be replaced.
Brian Jovag, owner of Jovag Home Inspection.