How to Insulate Concrete Floor Ducts

Insulating concrete floor ducts helps prevent drafts that can increase your utility bills. Applying a product that effectively seals concrete joints exposed to weather insulates the ducts well. Ductwork is often located in flooring to save space in crawlspaces or attics. It also reduces the loss of heated or cooled air, since the ductwork is shorter in this area.

Screwdriver (optional)
Compressed air or vacuum with attachments
Mastic gun
Two-part polysulphide concrete joint sealant
Putty knife

Instructions

- 1
  Remove any grills over the concrete ducts with a screwdriver before insulating the floor ducts.
- 2
  Clean around the ducts in the concrete floor. The sealant bonds more effectively if the surface is free of dust and other debris. Use a can of compressed air or a vacuum with attachments to remove the debris.
- 3
  Fill a mastic gun with a two-part polysulphide concrete joint sealant. Typically, this type of sealant contains a resin and a concrete curing agent.
- 4
  Squeeze the mastic gun to apply the concrete sealant liberally around the edges of the duct in the concrete floor.
- 5
  Smooth out the concrete sealant with a putty knife.
- 6
  Wait for the concrete joint sealant to cure according to the directions on the container before replacing any grills over the ductwork.

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