One key duct component you’ll hear mentioned regularly in the world of home performance is the venerable “floor-to-boot” connection.

It may sound like some obscure honky-tonk dance, but it is really one of the more important points in your home to investigate and seal when it comes to indoor air quality and efficiency. The floor-to-boot connection is the seam where the metal duct meets the subfloor. The included fittings usually consist of a round duct elbow and a rectangular duct box that fits up into the hole cut in your floor. The registers (aka grilles) you see around your house that deliver heat are fit inside this rectangular duct box. From the floor seam to the elbow, leaks at this point are important to address AND can also be the easiest to DIY.

Often, the material or nails that were installed to secure this piece of duct to the floor have been compromised, worn out or damaged. A gap can form around the edge that is a direct leak from the crawl space (yuk!) into the home. This is a passive leak when the furnace is not running and a forced leak point when it is.

This “broken boot” condition can also be a key indicator that other parts of your system may be compromised and a duct performance test is warranted.
See our articles on crawl spaces and duct leakage to find out more.