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 homeowner’s heating and cooling systems all around the country. Great strides have been made jacking up the energy efficiency of residential furnaces and air conditioning units the heart of your system. Federal regulations require the relative efficiencies of equipment be measured and prominently labeled with an “Annual Fuel Utilization Efficiency” (AFUE) if its a gas furnace and a “Seasonal Energy Efficiency Ratio” (SEER) number if its an air conditioning system.
The easiest way I tell my clients to think about this for furnace systems is, if the system is rated at 95% AFUE then every $1.00 you spend in gas, $0.95 of the dollar is staying inside your home and only $0.05 is being exhausted outside. For air conditioning systems I relate SEER ratings to MPG ratings with cars and trucks. The higher the SEER number the more “Miles” of cooling you get out of your system so the lower your electric bill will be.
Just a few years ago the normal SEER rating was 10, 11 or 12 for air conditioning systems but with Federal mandates, HVAC manufacturers are now only able to produce air conditioning systems with SEER ratings of 13 or higher. Often you’ll see contractors selling units with SEER ratings all the way up to 20 or even 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 15 will perform like one with an SEER of 9 or 11.
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 at the equipment/ductwork 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 blower system 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 unless a contractor takes extra measures to seal the seams.
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 Florida 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 like Town & Country and Home Depot 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 (its amazing to us contractors in the business that over 80% of repairs needed to furnace and air conditioning systems are caused by lack of proper maintenance and changing those dang air filters)!
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 system 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 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. If you think (or know) you have leaky ductwork, don’t wait to call your trusted HVAC professional so they can thoroughly examine your system and prevent you from going through another summer with high utility bills!
As a new section to my monthly column, please contact me with any questions or concerns you have about your home’s HVAC system. Your questions are probably the same questions other homeowners have and I would love to answer them. You can email (Garrett@CookHeating.net, mail (1002 Covington St. Crawfordsville, IN 47933) or even call my office (765-362-5300) and I’ll do my best to help you out.
