When you think about improved energy efficiency, what do you usually think about? More insulation? Energy-efficient windows? Turning off lights?

One thing that may not have occurred to you is the ducts for your heating and air conditioning system — but leaky ducts can account for as much as 40 percent of the air leakage in a house and contribute to poor air quality. In addition, uninsulated ducts in unconditioned spaces and poor duct system design reduce the efficiency of your heating and air conditioning system. Leaky ducts can also bring the dust and dampness from your crawlspace into your house.

If your plumbing is leaking, it's pretty obvious. Studies have found that most homes have some duct leaks, but these are generally undetectable to the average homeowner. Ducts are usually located in relatively inaccessible areas and are difficult to examine for leaks. However, high-tech equipment such as that offered with a Right Choice High Tech Audit can analyze duct system performance.

Why do ducts leak? Most modern ducts are made of a flexible material that can be damaged by sharp objects. Duct damage can occur when technicians working on something like installing cable or telephone outlets accidentally come in contact with the ductwork. Joints where two pieces of duct come together may separate over time. Duct systems deteriorate faster if they're not properly installed with sufficient supports.

Duct design is important as well. Improperly designed systems are less efficient and may result in uneven heating and cooling and excessive strain on your heating and cooling equipment.

You can do some simple things to make sure your duct system works as designed.

The duct system only works properly if air can circulate back to the return air plenums, the large vents that are usually found in a central part of the house. Don't block returns with furniture and make sure that air can circulate under closed doors. The filter is also an important part of the air circulation system and should be replaced or cleaned monthly or as recommended by the manufacturer.

Ducts in unconditioned spaces such as crawl spaces and attics should be insulated with fiberglass duct wrap. Insulating ducts that are in unconditioned spaces are usually a very cost effective way to reduce energy costs.

If you want to make sure your home is as healthy and energy efficient as it can be, check out the state of your ducts. A Right Choice High Tech Audit can help you find any duct problems and make sure that they've been repaired correctly.

A funny thing about duct tape...

Generally speaking, duct repair should be left to the professionals. If you try to fix obvious problems such as a duct that has separated at a seam, visible holes or unsealed joints, use silicone caulking or mastic-type sealant. Despite its name, the one thing that you shouldn't use duct tape for is ducts.

In 1998, scientists at the Lawrence Berkeley National Laboratory tested duct tape and 31 other sealants under laboratory conditions designed to mimic long-term residential use. They found that the one sealant that almost always failed was duct tape. Metal ducts should be attached together with sheet metal screws and flexible ducts should be attached with metal or plastic bands.