Most builders and designers involved with green building have heard of Henry Gifford. Energy efficiency experts admire his deep knowledge of heating systems and his straight talk about the unacceptably high number of HVAC problems in run-of-the-mill new buildings in the U.S. At the headquarters of the United States Green Building Council (USGBC), on the other hand, he is something of a pariah — due in part to his 2010 lawsuit that accused the USGBC of making “deceptive marketing claims.”
Gifford lost his suit. Yet even those who doubt the usefulness of Gifford’s litigious tactics usually admit that he has a point: many LEED-certified buildings use so much energy that they don’t even meet Energy Star standards. Due in part to Gifford’s needling, the USGBC has implemented changes in the LEED program that attempt to address some of Gifford’s concerns.
Gifford knows more about boilers and heating system design than almost any mechanical engineer in the country. I recently reached him by telephone for a one-hour interview.
Q. What recommendations do you have for the design of heating or ventilating systems for single-family homes?
Henry Gifford: A nice successful person, who society rewards with a three-bedroom house in the suburbs, usually gets a master suite with its own bathroom. Usually, the house has a duct system that blows 400 cfm of heating and cooling air into the bedroom all day. The air comes out the bedroom door, down the hallway past the thermostat, back into the central return near the kitchen, through the air handler and back around again.
At night, guess what happens? Somebody closes the bedroom door. Now the air pressure in the bedroom goes up, so now only 300 cfm gets delivered to the bedroom. Maybe 100 cfm goes through the bathroom exhaust duct through…