How To Insulate Sheet Metal Plenum

You can fasten and secure the ends of the batts with duct tape but that may cause the insulation to get spoiled.

How to insulate sheet metal plenum. Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct. If you do insulate the plenum the irc does require you to use a vapor barrier on the exterior of the insulation or use duct insulation blankets with integral vapor barrier and tape the seam s. Sheet metal ducts must first be tightly sealed resilient fibrous glass insulation thicknesses from 11 2 to 4 in. Do not use rigid foam insulation unless you know what the temperature rating is.

Ductwork is typically insulated with foil or vinyl backed fiberglass insulation specially made for the application. 38 to 102mm insulation boards fibrous glass insulation boards are also available for application to the outside of sealed sheet metal ducts housings and plenums. Duct wrap fiberglass insulation all seams need to be sealed to keep moisture out otherwise sweating may occur between wrap and sheet metal causing insulation to be damaged. Check for air leaks sealing them helps your system more than just the condensation problem.

If necessary switch the wires to reduce the blower to its lowest speed. Duct insulation may not pass through a fire wall or fire rated floor ceiling. Plenum should be dry before external insulation is applied. In this video this old house plumbing and heating expert richard trethewey helps a homeowner insulate his ductwork.