What to Use With the R-Value in AC & Heat Ducts

Sealant

• Even welded duct work should be sealed along each seam to prevent the leaking of hot or cold air from the duct. Cover seams with a mastic resin applied with a brush, taped using HVAC aluminum tape, or caulked using a urethane or silicone product. Duct tape, despite its name, is not effective in sealing duct seams.

Fiberglass

• Fiberglass mats or batting can increase the R-value of the duct work. It's easy to apply and inexpensive. Some fiberglass is made specifically to be wrapped around ducts.The fiberglass mats are 1 to 2 inches thick. You need adequate space around the duct work to install the bats. Fiberglass insulation will also help provide soundproofing between walls, as sound can travel from one room to another easily by reverberating off the metal duct work.

Duct Wrap

• Duct wrap is an aluminum-faced, thin wrap that uses trapped air bubbles to provide insulation around the duct. Wrap it around the duct and tape into place. Duct wrap is more expensive than fiberglass mats, but is easier to use in tight spaces.

Considerations

• High moisture areas, which may be a result of humidity from the weather or a humid interior environment, can cause condensation. This can lead to moisture damage in walls. Fiberglass mats hold moisture and can become saturated. Duct wrap is moisture-resistant.