How To Insulate Sheet Metal Plenum

Duct insulation may not pass through a fire wall or fire rated floor ceiling.

How to insulate sheet metal plenum.

Use foil faced insulation batts to wrap up the pipes but see to it that the whole thing is properly covered and any previous layers are thoroughly overlapped. 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. In this video this old house plumbing and heating expert richard trethewey helps a homeowner insulate his ductwork. You can fasten and secure the ends of the batts with duct tape but that may cause the insulation to get spoiled.

Ductwork is typically insulated with foil or vinyl backed fiberglass insulation specially made for the application. Sheet metal ducts must first be tightly sealed resilient fibrous glass insulation thicknesses from 11 2 to 4 in. Insulation used to externally insulate hvac ducts. Press a continuous strip of foil tape to all longitudinal seams along straight runs of duct.

Do not use rigid foam insulation unless you know what the temperature rating is. 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. 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 the speed of the blower motor on the furnace.