Proper ductwork design takes detailed planning in conjunction with your new home design or making smart cost-effective modifications for your remodeling project. Work with your trusted HVAC contractor to ensure that the five key elements of good duct design are adhered to, as outlined by the Air Conditioning Contractors of America’s (ACCA) Manuals J, S and D.

Sizing all systems

Your home, the ductwork, heating and cooling equipment and all other home-comfort systems (for example, zoning, air purification and whole-house ventilation) are, in essence, one system. Manual J is used to calculate the heating and cooling loads of your home, including a room-by-room assessment and the sum for the entire home.

The results of Manual J are used with Manual S to properly size your new heating and cooling systems, and those findings, in turn, are needed to accurately size your new ductwork, using Manual D.

Location of systems

A central location is best for your heating and cooling equipment. This ensures that duct runs are equally distributed, as opposed to running very long duct runs to one side of your home. With this in mind, good ductwork design utilizes conditioned areas, which include raised floors, sealed chases and drop ceilings. Ducts installed in unconditioned areas rapidly lose heat energy in the winter and gain it in the summer.

Sealing ductwork

Duct connections should be mechanically sealed with screws for physical durability, and then followed by mastic sealant compound to prevent air leaks. If you’re installing areas of flex ducts, butyl tape can be used to seal these seams.

Insulating ductwork

If you find that you must install ductwork in unconditioned spaces, even small portions, insulate these ducts using rigid insulation board or insulation rolls.

Leak and air-pressure testing

Your new duct system should be put to the test by your HVAC contractor using a blower door test. This will identify air pressure variances and leaks. Equal air pressure, or the movement of air, must be balanced through the supply and return ducts, and through the living space.

For more information, please contact us at Paschal Heat, Air & Geothermal in northwest Arkansas. For more than 40 years, we have taken pride in our quality service and installation for each individual project.

Our goal is to help educate our customers in Northwest Arkansas about energy and home comfort issues (specific to HVAC systems).  For more information about ductwork design and other HVAC topics, download our free Home Comfort Resource guide.

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