How do you know if your ducts need repairs?

There are numerous indications that the air ducts in your home are not properly sealed.  They include:

• Rooms are not comfortable, they are either too hot or too cold

• Your utility bills in the summer and/or winter appear to be too high.

• The heating and cooling registers do not have much air flow.

• The air filters in your main air ducts need to be replaced more often than once a month due to a buildup of dust and dirt.

• There are noticeable dust paths from heating and/or cooling registers.

• Duct work that resides in attic or crawl space areas is not insulated.

• Ducts made of flexible materials have noticeable kinks or sharp bends in them.

Can a homeowner make duct repairs?

Working with ducts is not brain surgery!  Most home handymen can make basic duct repairs and seal and insulate duct work.

Many heating and cooling ducts run in walls, however  you can start by investigating the duct work that is visible in areas such as attics, basements and crawlspaces.  In these locations you should be able to make basic duct repairs.

The first thing to look for is ducts that are no longer joined together, as shown in Figure 1.  After reconnecting the duct, that was separated, use a small sheet metal screw to secure the connection and seal the joint with proper HVAC grade duct tape - not the grey tape that is called duct tape.

Once all the obvious broken or damaged joints are repaired you can check to see if there are any air leaks at other joints.  To accomplish this turn on the heating and/or cooling system fan and place your hand near the duct work joints, if there is air leaking, you will feel it.  If you discover any joint leaks seal them with the HVAC grade duct tape or duct mastic. 

If you have air leakage where ducts penetrate ceilings or floors these can be sealed with a spray foam insulation. Of course, the areas in question, attics, basements and crawlspaces should all be properly insulated. 

The products that should be used to seal any air leakage in the ducts includes:

• A somewhat messy product that works extremely well is duct mastic.  Make sure that you purchase mastic that is produced as a duct sealant. 

• HVAC grade duct foil tape uses a thin piece of foil with an acrylic adhesive to provide adhesion to the duct.   Note:  Any products purchased to seal duct work should be approved under UL 181.

There is a basic advantage to using a HVAC contractor to perform these tasks as they will have the necessary specialty diagnostic test equipment to verify duct pressure and air flows to ensure that your complete heating and cooling systems are working to there appropriate design criteria.