An often overlooked area of potential energy savings is something that happens in places you can’t normally see — in your attic or below the floor.  The ductwork that carries conditioned air to the interior of your home is usually very underinsulated.

Even if your ductwork is sealed properly, if it’s not properly insulated you are losing conditioned air to your attic or basement.  

On a DIY scale from 1 - 10, I would rate a duct insulation project a 6.  Not much technical knowledge is required, but the difficulty rating is higher because you will most likely be working in cramped spaces and with materials that are hard to manage.  This project will take some time for planning and for the actual work.  Be sure take your time and do a quality job.  This may even be a job to outsource.  

Many resources recommend a rigid foam board insulation, but I would use a foil backed insulation that is easier to wrap.  You can tape the insulation in place with a foil-backed tape made for HVAC type applications.

From EnergySavers.gov:

Ducts are typically made out of thin metal materials that easily conduct heat. Therefore, uninsulated or poorly insulated ducts in unconditioned spaces can lose through conduction 10%–30% of the energy used to heat and cool your home. The heating and cooling equipment then has to compensate for the heat loss and gain by conditioning additional air. This added conditioning raises a homeowner’s energy bills.

A 10% - 30% savings?  This project has been toward the top of my list for months, but I haven’t taken the time to do it.  Since all of my air supply ductwork runs through my slab, I would only be insulating the return air duct.  Still, this is a big job and shouldn’t be taken lightly.

However, at up to 30% savings in your HVAC energy bill, even a sizable investment in insulation is likely to pay off. 

Photo credit:  Lawrence Whittemore