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Duct Sealing

Your new or existing cooling and heating equipment is only as good as the system that delivers air to every room. Central air conditioners, heat pumps and forced air furnaces rely on a system of ducts to circulate air throughout your home. To maintain comfort and good indoor air quality, it is important to have the proper balance between the air being supplied to each room and the air returning to your cooling and heating equipment. Leaky ducts can cause an unbalanced system that wastes energy. Sealing your ducts is one solution that can improve your system’s ability to consistently cool and heat every room in your home.

Whether you’re having new equipment installed or working to improve the performance of your existing cooling and heating system, you should have your duct system checked. If you’re not sure if you need to get your ducts checked, try the diagnose your ducts quiz.

Most duct improvement repairs require the assistance of a contractor. A good contractor will: 

  • Identify any duct leaks with diagnostic equipment.
  • Seal your ducts with mastic, metal-backed tape, or aerosol sealant. Duct tape should not be used because it can not withstand high temperatures and will not last.
  • Test airflow after ducts are sealed.
  • Insulate your ducts where it counts to keep the air at its desired temperature as it moves through the system. The contractor should use duct insulation material rated at R-6 to insulate ducts located in unconditioned spaces such as an attic or crawlspace.
  • Conduct a combustion safety test after ducts are sealed to be sure all gas or oil-burning appliances are working properly.

What are the benefits of duct sealing?

There are a number of benefits associated with sealing your ducts to meet the ENERGY STAR Duct Specification including health, safety, comfort, saving money, and protecting the environment.

  • Health: Air may leak into your duct system if it is not sealed properly. This can be harmful to your health because air leaks in the return duct may contain fumes from household and garden chemicals, insulation particles, and dust. These items can aggravate existing asthma and allergy problems. Why take the risk? By simply upgrading the energy efficiency of your duct system, you can avoid potential health problems. 
  • Safety: Safety in your home should be your number one priority. Duct leaks can cause equipment to backdraft (i.e., when combustion gases flow back into your home, instead of out the vents). If fireplaces, wood stoves, water heaters, furnaces, clothes dryers or other combustion devices are in these depressurized areas, invisible gases, such as carbon monoxide (CO), can backdraft into your home instead of going up the chimney. Make the smart choice and choose to seal your ducts. 
  • Comfort: Duct leaks and improper duct sizing can affect the comfort level in your home by keeping some places cooler or warmer than others. The source of discomfort in your home may be leaky ducts or improper sizing. Sealing your ducts can help you breathe easier by improving your indoor air quality, reducing the risk of pollutants entering and circulating through your home. They also save energy and money. 
  • Save Money: Leaking ducts can decrease the overall efficiency of your heating and cooling system by as much as 20%. Duct sealing increases efficiency and lowers your energy bills. The typical family could save up to $150 annually.
  • Protect the Environment: Energy generation and use is the single largest contributor to air pollution. If you’re wasting up to 20% of your heating and cooling systems’ performance through leaky ducts, your home is using more energy to get the same job done. By sealing your ducts and reducing the amount of energy necessary to comfortably heat or cool your home, you will reduce the amount of air pollution generated. 

Ducts Resources

Below are links to related sites and information. These links will take you out of the ENERGY STAR Web site.

The articles below warn about some of the failures of cloth duct tape:

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