The US Department of Energy:

http://www.eere.energy.gov/consumer/your_home/energy_audits/index.cfm/mytopic=11200

Thermographic Inspections

“In addition to using thermography during an energy audit, you should have a scan done before purchasing a house; even new houses can have defects in their thermal envelopes. You may wish to include a clause in the

contract requiring a thermographic scan of the house.”

Thermal Imaging is the ultimate in non-destructive testing for building envelope analysis. When focused on the walls of a house it can reveal the presence of the structual members in the walls (studs), and the temperature of the wall between them.  Because we know the R-value of 2x4's and 2x6's (1.41 R/inch), we can deduce the insulation value of the walls between the studs.  In older homes it is not unusal for me to find walls that are completely empty of insulation.  I also find homes with blown-in cellulose insulation, that are missing insulation in sections above and below windows.  Additionally, the insulation (cellulose) can be blown in incompletely, or can settle.  The Thermal Imaging camera provides the only way to find missing insulation in this situation.  It can display with pinpoint accuracy the locations where insulation should be added, where water is intruding into the house or where condensation is forming.