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Why do Homeowners Need to Seal Ducts?

1. To improve indoor air quality.  Duct leakage draws air from attics, garages, and crawl spaces, which often contain mold spores, insulation fibers, pesticide powders, exhaust fumes, radon, moisture, and more.
2. To improve comfort.  A good rule of thumb for the Southeastern United States is air conditioners typically lose a ton of cooling capacity (12,000 Btu/hr) under peak load conditions. Duct leakage causes the indoor air to be too dry in winter and too humid in summer.
3. To save money.   If ducts are outside the thermal envelope like crawl spaces and attics, research studies have proven that heating and cooling savings average about 20% from sealing leaks. However, similar studies have also shown savings of more than 40% are common.
4. To prevent moisture damage.  When supply ducts leak in hot and humid climates, concealed condensation inside duct work systems will often cause mold growth.

How Do Duct Leaks Affect Heating and Cooling Equipment?

Duct sealing can make the difference between a mediocre comfort system and an excellent one. Duct sealing improves the quality of an installation by enabling high efficiency systems to truly deliver their full capacity and efficiency. According to GA Power Company, if the duct leakage is 20% of the total air flow, the efficiency of the cooling system can drop by 50%. Heating efficiency is similarly affected. Duct leakage also lowers the heating and cooling capacity, and can shorten equipment life.

How Do I know if  My System Has Duct Leaks?

Always start with a simple visual inspection of the system. Today’s energy codes require sealing of  duct work joints. The difficult part of finding leaks is that most are not readily visible. The best method to determine if you have serious leakage requires a pressure test of the ducts with a special fan. This testing is often called a blower-door test and takes about an hour. This test requires temporarily taping over all the registers, then blowing air into the duct system with a fan to determine the amount of leakage as well as the location of the leaks. Before and after leakage measurement is the only way to ensure homeowners get what they paid for. Most heating and air conditioning companies charge a fee to conduct this testing, while www.bardi.com performs this test at no charge for Atlanta homeowners.

Why is Duct Leakage Common?

Duct leaks are often caused by using poor quality sealing materials. Experts recommend duct sealing mastic– a thick paste, usually water soluble, which can be used on all duct materials and provides a permanent seal once it dries. This mastic comes in tubs and tubes and costs around $20 per gallon. Most of the common duct tapes do not provide a permanent seal. Their adhesive dries out. Studies have shown that, for a new system, the cost of material and labor to seal all the joints with mastic should be about the same as for a quality job sealed with tape.

Where Are the Most Important Areas to Seal?

A visual inspection should reveal disconnected components. This type of leak usually causes the greatest loss of a system’s efficiency and should be your highest sealing priority. Next highest sealing priority is the connections between the air handling unit and the air space, called plenums. Final in priority, seal takeoffs, boots and other connections where branch ducts connect to the main supply or return trunk line. Share this priority list with your heating and air conditioning experts as you price duct work sealing.