Imagine getting a heart transplant only to find out afterwards that you have clogged arteries. No doubt you would end up suing the heart surgeon and operating team for neglect.

Something like this commonly happens to home and building heating, ventilating and cooling (HVAC) systems all around the country. Great strides have been made jacking up the energy efficiency of HVAC furnaces and central air units - the heart of your system. Federal regulations require that the relative efficiencies of this equipment be measured and prominently labeled with a "Seasonal Energy Efficiency Ratio" (SEER) number. Just a few years ago the normal SEER rating was 8 or 9. Now many contractors sell units with SEERs of 12, 13 and higher. This theoretically saves the home owner hundreds of dollars each year in energy costs.

Unfortunately, despite paying thousands of dollars to replace antiquated HVAC units, many home owners are not deriving the full benefits of their advanced equipment due to damaged arteries, i.e., leaky duct systems. Too often they hook up high efficiency equipment to an energy-guzzling duct system. Studies have shown that when this happens, an HVAC unit rated SEER 12 will perform like one with an SEER of 6 or 8.

Ever wonder why some rooms have always been very hard to heat or cool? Or why your HVAC system costs so much to run? Or why your house always seems too dusty? Any and all of these problems may be caused by leaky ductwork.

The leaks may be tiny and subtle, occurring at collars, joints and the air handling interface. Careless construction crews sometimes damage the delicate ductwork during original installation, or maybe the home owner will do it inadvertently during spring cleaning. Over time joints come loose and duct tape falls apart. Even if it's a small hole, when the equipment's air handler is turned on, air pressure in the ducts increases 15 to 30 times. This forces air to escape like out of the narrow stem of a blown-up balloon. Also, wall and joist cavities often get used as return air ducts and plenums. These are never airtight.

Individually, none of these leaks may amount to much, but the cumulative effect is to dramatically reduce the operating efficiency of your HVAC system. One study done by the New Jersey Governor's Energy Office concluded - "It can be projected that duct leaks increase total cooling and heating energy use in Florida by about 33%." That's an amazing figure when you think about it. Imagine saving 33 cents out of every $1 you pay in energy bills. Over the course of a year that adds up to some real money!

Minor duct leaks can be detected and fixed by home owners themselves. While the system is running, feel along the ducts for hot or cold air escaping. When you locate minor leaks, you can plug them with silicone sealants made especially for duct systems.

Hardware stores also sell special aluminized tape that is more effective than duct tape for wrapping around duct joints and bends. Also be sure to keep the filters clean on any forced air system. They should be replaced no less than one a quarter for optimum performance.

While these do-it-yourself fixes will solve minor problems, more serious cases would benefit from an examination by a home heating and cooling professional. Sophisticated firms use what's known as an infiltrometer blower door test, using technology developed with government funding by Princeton University scientists. This examination usually takes less than an hour. The device fits snugly into a door opening. While your air handling unit is shut off, a fan pressurizes the house. The technician then uses chemical smoke to evaluate duct leakage from inside the home. The smoke should just linger in front of a register or grille. If it races in, it means there are duct leaks nearby. A thorough technician will be able to compute the combined amount of leakage by repeating the test after temporarily taping over registers and grilles.

Homes in New Jersey with duct leaks in attics and crawl spaces often will draw that hot, dusty, moldy air into conditioned space. This not only wastes energy, it can be a health hazard as well. This is why, in addition to testing for duct leakage, people living in older homes should consider having their ducts cleaned to remove years of accumulated dirt and grime that contribute to allergies and other ailments.

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