If you live in New England, you know that furnaces are installed in basements. But any New Englander who moves to Oregon soon learns that furnaces are installed in garages. And anyone who retires to Texas discovers that furnaces are installed in unconditioned attics.
Of course, there are many other examples of similar regional differences in construction practices. But this is one regional difference that matters. New Englanders have it right: furnaces and ductwork belong inside a home’s conditioned space, not in the great outdoors.
If you build in a region where ducts are usually installed in unconditioned attics or ventilated crawl spaces, it’s time to get with the program and learn how to bring your ducts indoors, where they belong.
Unconditioned attics, vented crawl spaces, and garages are cold in the winter and hot in the summer. Since most duct systems are leaky and poorly insulated, duct systems installed outside a home’s conditioned envelope waste tremendous amounts of energy.
According to Dave Roberts and Jon Winkler, engineers at the National Renewable Energy Laboratories, ducts in unconditioned attics waste about 20% of the output of a furnace or air conditioner. These researchers report that during peak conditions, the losses are even greater. Roberts and Winkler wrote that in Houston, Phoenix, and Las Vegas, “The average DSE [distribution system efficiency] for the three locations on the design day, which would be considered the day of the season when cooling demand is highest, is 72%. This means that on the hottest day of the summer, 28% of the air-conditioner output is ultimately lost.”
These calculations assume that attic duct connections are all intact. However, as any home inspector knows, attic ducts are often crushed, ripped, or completely disconnected. Since homeowners rarely visit all the nooks and crannies of their attics, these problems…