Duct Systems and Bad DuctworkBad Ductwork - Ductwork is necessary to deliver the air throughout the HVAC system. It is important that the system has integrity with no leaks. Duct work is made of different materials. Duct systems also have different construction methods which hold the ductwork together.

Pictured above is an old ductwork system (which needs to be replaced) made of duct board, which is a rigid fiberglass board, and flex duct work. The duct board is cut to size from the duct work sizing requirements for tonnage and taped together with special duct tape. For the branches coming off the duct board trunk, metal collars are inserted into holes cut to size in the duct board. Flex ductwork is attached to the metal collars for the branch ductwork.

Bad Ductwork Made into Good Ductwork

The metal collar is sized to the size of the flex duct branch and the flex duct is attached to the metal collar with special duct tape and a large panduit strap. Some HVAC installation mechanics also use a sealer in the metal collar where it is inserted into the duct board and on the flex duct connection. This makes the connection better and ensures there will be no air leaks at the connection as long as the sealer is covers all connections. Flex duct should have few turns in the runs and be pulled taught. Installed in the manner reduces the friction on the airflow by reducing turbulence in a duct system with minimal bends and turns.

Duct work systems are also constructed of sheet metal. These sheet metal duct systems are manufactured or pre-fabricated in either round or rectangle duct work. This duct work can be connected either using mechanical joints called Slips and Drive, snap seams, or by screwing it together. Either way, all seams in the duct system should be sealed with sealer to prevent any air leaks. Duct work also needs to be insulated for a few reasons. First of all, so that the conditioned tempered air is delivered to the designated spaces without loosing all it’s conditioning through heat loss and heat gain as it travels through the duct work. Secondly, the duct system needs a vapor barrier to prevent sweating when humid conditions exist outside of the duct work.

A good duct system will deliver the air to the designated space with no air leaks and with little heat loss heat gain while it traveling through the duct work.

You can find ductwork tools and accessories for ductwork repair here.

High Performance HVAC

Duct Systems and Bad Ductwork

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