How to Repair Air Ducts

Have you been paying a lot every month for your electric bill? Have you always wondered why your electricity have been reaching its highs no matter how much you conserve energy by turning off your appliances and lights when not in use? But the real question is this. Does it really have something to do with your lights and appliances? Or maybe you are not aware that there had been a problem with your air ducts?


Poorly sealed air ducts can be one of the biggest energy and money losers at home. If you are much confident with your insulation wraps, that doesn’t solve the problem or it does not stop air leaks. Now, here are some ways on how you would repair air ducts.

• How to Seal Air Ducts with Mastic
Mastic seals are faster to apply than tape. They also last longer and seals better.
1. Clean the surface with a damp cloth if it is filled with dust, oily film, and grease.
2. Load brush with mastic and cover the entire joint continuously. Use the end of the brush to work the mastic into joint. Spread mastic atleast one inch on each side of the joint and it should be thick enough (about1/16 inch) to hide the metal surfaces.
3. If the gap is greater than ¼ inch in the duct connection, then use fiberglass reinforcing membrane in addition to mastic. If it is too sticky on the side, cut enough membrane to cover the joint, press it in place, and then cover with mastic. To completely cover the membrane, apply enough mastic. However, if the membrane doesn’t have a sticky side, apply a thin layer of mastic, press the membrane then apply the finishing layer of mastic.
4. Wrap ducts with insulation. It can be installed over wet mastic but try not to move the ducts too much for it could damage the mastic seal. Before applying the mastic, make sure that you’re done with all the duct support work.

• Round to Rectangular Transitions
Fiberglass reinforcing membrane may wrinkle when it’s run along a joint between round and rectangular ducts. Use a utility knife to make it flat, make a series of slices about every 2 inches then wrap it around the duct.

• Mastic Recommendations
Use a UL 181A-M and UL 181B-M. These types of mastic are designed for the repair and installation of ducts. It can be applied through brush, gloved hand, trowel, or caulking gun. Even though mastic is still wet, you can already apply insulation.

Now that you have learned on how to repair your air ducts, surely you won’t have any more problems with your electric bill. And when the time comes that you’ll notice your bills running high once again, you will never fail to check your air ducts and be ready to repair them.