Duct Sealing

Ducts that leak to the outside are bad and can cause a number of problems. Ducts that leak to the inside of the building are less serious, but should be sealed to make the system operate efficiently.

We seal ducts that are outside of the building envelope with two-part polyurethane foam. This not only seals the gaps and holes that are typical in almost every installation, but it also insulates them far more effectively than any duct wrap or duct board. Our Zerodraft foam is a vapor barrier, an air barrier, a superior insulator and gives the ducts extra strength and support.

Ducts found inside the conditioned space are sealed with mastic and sometimes with UL-181 mastic tape. Mastic is spread over all of the joints and penetrations in the ductwork. Duct tape should never be used on ducts because it just doesn’t work. We don’t know why they call it duct tape.

It is most important to seal return ducts that run near any combustion equipment such as the furnace or water heater. The suction that is created by the return may be enough to backdraft these appliances, drawing flue gases - such as carbon monoxide - into the living space.