Mastic Duct Sealant

Above is an HVAC duct. The day I visited the day site the HVAC subs were behind and had to stay late because the ducts were not sealed yet. The mastic duct sealant helps to provide a stoppage against leaking in the ductwork, it is NOT to hold the ductwork together. That needs to be done with hangers, bolts, and screws.

The mastic sealant is a flexible sealant that takes the shape of the material which you are applying it to. According the the Green Building Library, most of the energy loss in a house comes from your HVAC ducts. The loss can equate to 20 to 60% of the air leakage in a home. So ensuring that your home or office properly sealed is very important to reduce your heating and cooling bills. Also, the mastic sealant is being used in commercial work, but is making its way into residential applications as well.

The sealant actually never hardens, so it can withstand the expansion and contraction of materials. The material also acts as a barrier to moisture.

There are other ways to seal ductwork as well. Tape, such as a mesh tape. The tape is similar to drywall tape but is has a different width and is also reinforced with fiberglass. In order to make the best seal on ductwork, use both the tape and mastic sealant. This will ensure a tight seal.

Areas which should be sealed are: around the air-handler, transition or different connections, where a solid connection meets a flexible connection- there is obvious movement from a flexible to a rigid connection, and in building cavities.

For more information on mastic and mesh tape sealants for HVAC usage, visithttp://oikos.com/library/ducts/index.html

More photo's below of different sealant areas.