In this video, This Old House plumbing and heating contractor Richard Trethewey quiets a whistling heating duct.
1. Mark the location of a start collar on both the return- and supply-side duct.
2. Cut holes in each duct using a sheet metal duct cutter attached to a drill/driver.
3. Screw a start collar to the return-side and supply-side ducts.
4. Install elbows to each end of a bypass damper.
5. Attach the bypass damper between the two start collars, effectively connecting the return duct to the supply duct.
- Bypass damper, used to quiet a noisy duct
- Start collars, for attaching bypass damper to existing duct