Sealing Your Ducts for Better Heating

They’re the least visible but most far-reaching part of your HVAC system. They allow the conditioned air to reach every room in the house. They’re the ducts and although yours are probably doing their job just fine, there’s always room for improvement. Most people don’t know this but there are plenty of reasons to take a look at your ductwork occasionally to make sure they’re in great working order. You may think something as simple as a passageway for heated or cooled air can’t need all that much attention and although it is true that ducts don’t typically require regular maintenance to maintain their working order it isn’t true that there’s no worth in adding some improvements and cleaning them out every once and a while.

The purpose of this tip of the day will be to illuminate you on some of the possibilities for ductwork improvement and maintenance and what the benefits are. Specifically, we’re going to be focusing on one aspect of ductwork improvement that is often overlooked, sealing your ducts. Sealing ducts will lead to greater energy efficiency in your home and make your heater and your air conditioner’s job easier.

What is Duct Sealing?

Simply put, the bottom line is that a duct system that is well-designed and properly sealed can make your home more comfortable, energy-efficient, and safer. Your air ducts are one of the most important systems in your home, and if the ducts are poorly sealed or insulated they are likely contributing to higher energy bills. Your home's duct system is a branching network of tubes in the walls, floors, and ceilings; it carries the air from your home's furnace and central air conditioner to each room. Ducts are made of sheet metal, fiberglass, or other materials.

Ducts that leak heated air into unheated spaces can add hundreds of dollars a year to the cost of your cooling and heating in Austin, but you can reduce that loss by sealing and insulating your ducts. Insulating ducts in unconditioned spaces is usually very cost-effective. Existing ducts may also be blocked or may require simple upgrades. Sealing ducts essentially just means reinforcing the connections where the ducts meet the walls and one another and making them less capable of leaking air. It’s a simple concept with wide-reaching ramifications.

Sealing Ducts with Mastic

There are two main options you have for the sealing material in your duct sealing project, mastic and duct tape. Mastic is the most common form of sealant these days so we’ll go over this method first. Of course, this project can be done by a professional and that is going to pretty much guarantee you a good outcome if you hire a reputable Austin heating company but it is still worth knowing how the process works. Some people choose to take on this home improvement project DIY style which is entirely possible with a little patience and know-how.

There are ways of designing the ductwork system in your house such that loss of heat isn’t a problem but this tip of the day is assuming that this project is going to be a retrofit and not a part of new construction. And most people have ductwork that isn’t designed to minimize heat loss. This means the ducts are in areas of the house that aren’t a part of the livable spaces. Sealing your ducts to prevent leaks is even more important if the ducts are located in an unconditioned area such as an attic or vented crawlspace. If the supply ducts are leaking, heated or cooled air can be forced out of unsealed joints and lost. In addition, unconditioned air can be drawn into return ducts through unsealed joints.

To get started sealing your ducts with mastic you’ll need a few materials. You’ll need a gallon bucket of mastic, Duct Seal 321 will work. You’ll need three-inch self-stick fiberglass mesh reinforcing tape for large joints. You’ll need a soft bristle short brush to apply the mastic. You’ll need scissors for cutting the fiberglass tape and you’ll need a plastic sandwich bag for storing the wet mastic brush for reuse.

What is mastic in the first place you may ask? Mastic is a permanently flexible, indoor and outdoor rated, gap-filling sealant that sticks to sheet metal, foil-faced insulation, wood, and most materials. Because it’s a gooey (like peanut butter) brush-on product, mastic conforms to any shape and contour. This makes it easy to apply and easy to conform to any shape the ductwork in your house may present.

The fiberglass tape should be used as a support to the mastic and not as the primary means of sealing. Fiberglass mesh reinforcing tape is needed to support the mastic across larger gaps, such as here where the start collar meets the duct board plenum. This fiberglass tape for sealing HVAC ducts with mastic, do not use fiberglass tape made for drywall joints. Scissor cuts are made about half-way through the 3-inch wide self-stick fiberglass tape so it will wrap around the start collar and lay flat against the plenum. Take care the surfaces are clean, oil and dust-free before applying the tape and mastic.

The fiberglass tape should also be applied to the far end start collar and duct board distribution trunk duct. Brush on the mastic, working it into the joints and fiberglass mesh. The fiberglass tape should be used everywhere in the ducts where there is more than a 1/8th inch gap. Everywhere else the mastic alone needs to be applied. This will be applied at every joint and every connection within the ductwork.

Sealing Ducts with Duct Tape

Duct tape can also be used to seal ducts and it will certainly be better than no sealant at all, however common hardware-store duct tape, technically known as cloth-backed rubber-adhesive duct tape, fails quickly when used on ducts, most energy-conscious builders seal duct joints with mastic. But that doesn’t mean a duct tape is never an option. In fact, in some cases, it can have its advantages. Mastic can be messy to apply and awkward to use on clamped flex duct joints.

There are certain regulations for the tape used when sealing ducts. In accordance with the International Energy Conservation Code tape used to seal ducts must be labeled UL 181A or 181B. Though in reality, this label has more to do with fire protection than seal effectiveness. The effectiveness of a type of duct tape is going to depend mostly on what material it is made out of.

For sealing the inner core of flex duct to metal collars, as well as to repair the outer jacket of flex duct, many contractors have begun using oriented polypropylene tape, or OPP for short. The tape has a smooth backing and an acrylic adhesive said to be more tenacious than rubber adhesive. The backing can be manufactured in a variety of colors, including a shiny “metalized” plastic finish.

Another option is butyl tape. Foil-backed butyl tape performs much better than cloth duct tape, although it isn’t cheap. Many of these butyl material tapes have fared well in tests of sealant abilities. The butyl tapes have much more adhesive on them, so they will take longer to dry out and will stay flexible longer.

Duct Sealing Benefits

What it all comes down to is that both mastic and duct tape has their advantages and disadvantages. Mastic used to be the go-to but new types of tapes that are available now show many degrees of improvement over the cloth-based tape that used to be the standard. Since all duct-sealing products, including mastic and all types of duct tape, have disadvantages, deciding on the best duct-sealing strategy is tricky.

Most contractors use mastic as it doesn’t generally dry out and lose its adhesive as most tape tends to do but there are some specific areas where duct tape almost certainly needs to be used. High-quality duct tape, not mastic, should be used to seal holes in a furnace or air handler. This so that if repairs or maintenance service is needed in these areas they can still be accessed with ease. A tape can be taken off and reapplied, mastic cannot.

The benefits of this procedure are far-reaching and include improvements in comfort, air quality, safety, and energy efficiency. On the comfort front, sealing your ducts can help with common comfort complaints, such as rooms that are too hot in the summer or too cold in the winter. Less air leakage will mean a more even distribution of air throughout the house.

The air quality improvements stem from the fact that sealing your ducts means there’s less of a chance that containments such as pollen and other particles will enter the ducts through gaps and start to circulate through your household. The safety angle comes mostly from the danger of carbon monoxide that is present whenever you use heaters that burn gas. During normal operation, gas appliances such as water heaters, clothes dryers, and furnaces release combustion gases (like carbon monoxide) through their ventilation systems. Leaky ductwork in your heating and cooling system may cause “back-drafting,” where these gases are drawn back into the living space, rather than expelled to the outdoors. Sealing leaks can minimize this risk.

Of course one of the biggest and most attractive perks of having your ducts sealed is what you can save on your energy bill due to increases in efficiency and decreases in hot air leakage through gaps in the ductwork. Leaky ducts can reduce heating and cooling system efficiency by as much as 20 percent. Sealing and insulating ducts increase efficiency, lowers your energy bills, and can often pay for themselves in energy savings. Plus, if you’re planning to install new heating and cooling equipment, a well-designed and sealed duct system may allow you to downsize to a smaller, less costly heating and cooling system that will provide better dehumidification.

Duct Sealing and Heating Repair in Austin

The benefits of duct sealing are plentiful. Many homeowners may be surprised to know that their ducts are either not sealed according to regulations or just not sealed as thoroughly as they could be. This is a project that is well worth your efforts, regardless of whether you go through a professional or do it DIY. Whether you’re installing new ductwork or doing this as a retrofit, you can get a lot out of some simple duct sealing work regardless of whether you choose mastic or high-quality duct tape as your sealant.

And don’t forget that if you ever need any kind of heater repair in Austin, AC Express is the place to call. Thanks to our same-day heater service many satisfied customers throughout Austin have found their heaters back to working order in no time. We’re an Austin heater repair company that operates all around the Austin area, from Hutto and Manor to Pflugerville and Round Rock. If you’re in the need of expert heater repair in Austin don’t hesitate, call today!