(As a follow-up to our article in January Snips, "Study: perimeter ducts show no comfort advantage" we have received a complete copy of the two technical papers on which this article was based, and are able to provide further information on this interesting subject. The first paper is by Wendy Hawthorne, PE, and Susan Reilly, PE, both with Enermodal Engineering Inc., Denver, and was written with Ren Anderson and Edward Hancock in 1998. The second was published last year in ASHRAE Transactions and was co-authored by Hawthorne and Reilly.)

Heating ducts in a residential home typically are installed the length of the room and come up through the floor beneath the windows. This is known as perimeter heating, since the heat is released around the perimeter of the house, and dates back at least to the 1940s and 1950s research. But why is this done?