An architect, insulation installers, door and window salespersons/installers, and a mechanical contractor are in a classroom together, and the instructor asks: “Should you upgrade the building envelope or replace the heating and air conditioning equipment? You can only do one or the other first due to budget constraints.”

Only the mechanical contractor says HVAC equipment first and everyone mocks that answer. The energy audit instructor says, “Of course you’d say that — you sell HVAC equipment. Care to explain why you think you’re right?”

There’s only one problem: The mechanical contractor already crunched the numbers and had documented proof he is right. That contractor was me, and this really did happen.

So how do you diplomatically tell a room full of professionals they and the instructor are wrong? “Carefully, wary carefully,” as Elmer Fudd would say.

For one thing, the all-day class had just started and there was going to be a test at the end. Tick off the instructor and that test score might suffer! So, I told them that if they were referring to on/off HVAC equipment, they’re only partially right and here’s why.