Buildings

Performance Testing Duct Work

Q: One of my neighbors read an article that said leaks in the ductwork of your house can cause a big increase in your energy bills, and apparently there are companies out there offering to locate and repair your duct leaks. Is this for real or just another scam?

A: The first time I heard someone talk about duct leakage, I frankly thought they had gone quackers. It turns out, however, that duct leakage is a major factor, not only in your energy bills, but also in terms of your health, safety, and comfort, along with the durability of your home.

Studies done in North Carolina by Advanced Energy suggest that, on average, 15%-25% of what we spend for heating and cooling our homes is being lost through leaks in the ductwork. This is consistent with findings in several other states.

Even more important than the energy costs, however, are some of the other consequences of duct leaks. If, for instance, you have a leaky return duct in your crawl space, every time your system kicks on you'll be sucking crawl space air into your house. This means that your family is breathing whatever moisture, mold, mildew, or termite poison happens to be down there. A similar leak in the attic can be circulating dust, insulation particles, etc., throughout the house.

Another serious problem associated with duct leakage is the creation of negative pressures in various part of the house which can cause combustion appliances like fireplaces, water heaters, and furnaces to back draft and spill carbon monoxide into the house.

One reason for being skeptical is that things like "negative pressures" can't be seen or even felt, and it would be easy for someone to claim you have a problem when you don't. Another reason is that ducts have been in houses for decades. Why is this a problem all of a sudden?

The fact is that the tools and equipment needed to diagnose these problems in an affordable manner have only been around for several years. Very accurate digital pressure gauges and carbon monoxide detectors didn't exist a few years ago. Machines that can pressurize the duct system and measure the leakage have only come into existence over the last decade. The problems have existed for as long as we've been moving air around the house to heat and cool, but our ability to measure what's really going on has changed dramatically.

The key is to find someone who has these tools and has been trained in how to use them. North Carolina is home to the finest duct diagnosis and repair training program in the nation, and over 175 people have gone through the program and are qualified to diagnose and repair duct leakage and pressure problems.

If you're building a new home, be sure to insist that you get a sealed duct system. This means that the ducts are sealed with mastic, not with tape, and have been tested. Some utilities have a duct-sealing requirement in their new home programs. North Carolina Power, for instance, requires duct sealing in their Energy Saver Plus program, and they actually test the houses for compliance. Check with your utility to see what they offer.

Duct leakage is fairly easy to eliminate in new construction at minimal added cost. In existing homes, repairs can often be made at reasonable costs as well. Given the payback in terms of reduced energy bills and cleaner indoor air, it's well worth it.