It takes an entire day, at least for my old house (1949). They tested the houses efficiency in holding pressurized air - which was surprisingly good - and sealed some ducts and other things to improve it. I got some good advice about what improvements would be most cost effective for my house. And in my case, the co-pay was covered (I think by the town) so all it cost me was a day off work. Staff were knowledgeable and friendly, I enjoyed their company.
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