It's the Duct's Turn for Retrofits

Pity the poor neglected duct. Put end-to-end, there are enough of them in American homes to reach to the moon and back. Yet for years the duct's energy aspects have been ignored by researchers. To energy specialists, ducts simply connected two much more technically interesting aspects of a house's heating and cooling systems, the furnace (or air conditioner) and the building envelope. The building envelope, with its many opportunities for retrofits, garnered the most attention. Meanwhile, furnace and air conditioner efficiencies have been pushed ever upwards by federal standards.

Now it's the duct's turn. Or, more accurately, now it is time for thermal energy distribution systems to receive their share of retrofits. Part of this issue of Home Energy is devoted to articles about improving the distribution of heating and cooling in homes.

These articles span our knowledge of distribution systems. It will immediately become apparent that the research is not yet complete. Indeed, even key concepts, such as efficiency have not yet acquired standard definitions. This is not surprising given the variety of diagnostics, retrofits, and buildings examined. These articles are more snapshots of current thinking than the final word. Still, they demonstrate that distribution systems in most American homes are rarely working as designed and are almost always major opportunities for energy conservation retrofits.

A house's distribution system is closely linked to unexpected activities. For example, a leak in an air duct may cause depressurization, leading to spillage into the house of exhaust fumes from gas appliances. In other cases, the efficiency of the air distribution system will depend on the pattern of air infiltration leaks in the shell.

The traditional techniques to construct and repair air distribution systems are laughably poor. That old standby, duct tape, has been implicated as one of the worst offenders; a more accurate name would be temporary tape. The new techniques, described in this issue, emphasize measurement and more quality control. This is not surprising because an incorrect retrofit will often lead to an even worse condition.

This special issue provides fewer final recommendations than usual. Nevertheless, it is an opportunity to capitalize on the latest research results and observe the work of some very creative and dedicated researchers and practitioners.

Alan Meier