The thermal barrier is made up of the air barrier and the insulation barrier and they should be touching each other on the same plane. Get this wrong and your power bill will remind you every month that the guy in the travel trailer was not the best deal. What About Existing Homes?: The process for an energy efficient house is a little different if the house was built in 1975. In this case, the first step is like going to the Doctor – The Doctor knows, let him or her diagnose the problem and the best course of action.