Between rising energy costs and concerns about environmental sustainability, more and more homeowners are attending to energy loss caused by nagging duct leaks. Duct tape and mastic represent the two principal methods of eliminating such leaks. If you would like to learn more about what distinguishes each of these methods, read on. This article will provide a heating contractor's knowledgeable comparison of these two duct sealing tactics.


Some sort of sealer has to be used to prevent air from escaping virtually anywhere two sections of HVAC duct are joined together. Many HVAC installers utilize mastic for this purpose. Mastic consists of a gooey, thick substances that is applied to such joints with a paintbrush. The idea is that the mastic is able to squeeze into any gaps--no matter how minute--thus keeping air inside of the duct.

Duct Tape

The first thing to realize here is that what most people refer to as duct tape--that grey, cloth-backed tape--is not really suitable for use on HVAC ducts. It's adhesive simply isn't designed to stand up to the heat and expansive forces, and will soon grow brittle and give out. Instead you will want to use either what is known as oriented polypropylene tape (OPP) or butyl duct tape. When wrapped tightly around clean ducts, these tapes are constructed to provide maximum durability as time goes on.

Pros and Cons

Mastic has a couple of key advantages over duct tape. For one thing, it is able to provide great results without clamping. In other words, external mechanical fasteners do not necessarily need to be used. That said, mastic alone is not strong enough to prevent a duct joint from coming open. Larger gaps or holes will require the use of reinforcing agents such as metal screws.

Mastic is also useful in that it can be successfully implemented regardless of the metal's cleanliness. This can save a lot of time and energy where installation is concerned. Duct tape, on the other hand, requires that a joint be cleaned prior to installation. Otherwise the bond simply won't be strong enough to last the test of time.

Cleaning aside, the actual process of sealing ducts with tape tends to be much simpler and cleaner. Before getting involved with mastic, it is important to recognize that it will be a messy process. You'll need to wear old clothes and full rubber gloves. It may also be necessary to add several layers of mastic in order to get it to the necessary thickness. This increases the time consuming aspect of working with mastic.

For professional assistance with sealing your HVAC ducts, reach out to companies like Ronnie Ritchie Service Co Inc.