What are the Different Types of Ductwork?


What are the different types of duct work?

Some of our Maryland readers may be surprised to learn about the different types of ductwork running inside their homes. Many folks have seen exposed, rectangular-profile metal ducts in businesses and assume those are the only type of ductwork in use. When paying an HVAC contractor to install ductwork for central air, you will quickly learn of the many types of air ducts, each useful in certain installations.

No One Size Fits All

No One Size Fits All

JJ Heating & Cooling Company


Ducts come in different materials, profiles and sizes. Ducts can be flexible or rigid. They can be metal, plastic or combinations of materials. No one size duct fits all applications. The many HVAC duct types have been developed to fit the many situations HVAC installers encounter in Maryland area homes.

Sheet Metal

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HVAC contractors have relied on 30-gauge galvanized steel ducts for decades. It is still the stuff of spy movies (folks crawling through ducts), but is expensive and challenging to install. For most homeowners, new construction will not use metal ducts except for, possibly, a main trunk.

Sheet metal ducts can have fiberglass insulation either inside them or around their outsides, greatly increasing their energy efficiency while reducing noise. If the insulation is inside, it is susceptible to holding moisture and airborne contaminants.

Flex Ducts

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A Maryland home with a main supply trunk of sheet metal may have flexible ducts branching off it. Each room should have a supply line sized for its air volume, so flexible ducts come in many diameters. They are built using flexible plastic around a wire coil and covered in thick insulation. They can be fitted rapidly, hold their shape well and can be secured easily.

Flexible ducts need support, however, so a high-quality installation will not leave ducts simply draped around an attic or crawlspace.

Duct Board

JJ Heating & Cooling Company

Imagine fiberglass insulation – the kind you see in attics, between the joists – stiffly adhered to a foil or fabric layer. That is duct board, which is not particularly strong but does insulate extremely well. The insulation is on the inside, so it can trap dust and contaminants. Duct board can solve installation dilemmas, but must be installed with care.

No Duct Tape!!!

Though “duct tape” seems to be named as an accessory for home ductwork, no good contractor uses it. Instead, expect and insist on mastic or metal tape. “Duct tape” is intended for temporary fastening and does not guarantee secure seams and fittings.

To get the complete story on the right ductwork for your Maryland-area home, contact the professionals of JJ Heating & Cooling Company. We can advise on new construction, inspect your existing ductwork and make repairs to leaky ducts. Contact us today, and be sure to ask about our duct cleaning specials!