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Energy Saver: Furnace, Boiler & Woodstove Combustion
(continued ...) that the air could be below freezing in some areas and could be a hazard to water piping. Add insulation to nearby piping that could be affected. Also, since the air may be very cold the duct could sweat if you do not insulate it. Add no less than 2 to 3 inches (5 to 8 cm) of fiberglass blanket with an aluminum-foil-fiber-reinforced-paper jacketing along the length of the ducts. Seal the insulation jacketing joints with 2 inch (5 cm) wide aluminum tape, also available at your home center.
But wait, you are thinking, "I now have two gaping holes in the side of my house that are ducted to my mechanical room I didn't have before." And you would be right *6. This does not apply to equipment without an electric control circuit, such as a simple wood stove. If you already have outside air duct(s) or opening(s) or as an intermediate step to adding same, I will now discuss adding some opposed-blade-dampers to those outside air openings. (There may be an alternative to this that I will discuss in a minute.) The best place would be right on the back of the louvers, before you transition to the round duct. Better dampers are normally square and in this location you can close off those outside holes when not needed. Pick dampers that have good blade seals. The dampers need to have spring-return-to-close actuators. Since I will now describe tapping into the boiler or furnace control circuit, a loss of power means you have no flame either. Hence, upon power loss the dampers close, keeping the cold air out.
Obviously, before doing anything else, turn off the power at the breaker and shut off the fuel valve as applicable. You're going to work on your machine *1. ...