Someone suggested I use my $100 infrared thermometer to check circuit breakers. That seemed like a good idea and it works fine. Then I ran into an engineer who uses it in a number of ways during energy audits (scroll down to "Energy Auditing Techniques). He has some good information in there including how to spot failures in the building envelope using the thermometer and some other relatively inexpensive instruments.
It’s all beyond the scope but if you want to check out the possibility of doing energy audits This is a good place to start. Free checklist, too.
It’s a lot less expensive to become qualified to perform energy audits than it is to become qualified to perform energy rating.