By Barbara Kessler
Green Right Now
You can hear them rattle in the winter, and rumble in the summer. Whether they’re underfoot or overhead in the attic, these unseen monsters can really make a difference in your home’s heating and cooling bills.
Yes, we’re talking about your ducts or duct work, and we don’t mean to be personal when we say, you’d better have your ducts in order when it comes to saving on cooling costs.
Leaking ducts typically drain away 20 to 25 percent of the cool air your air conditioning unit is trying to pump throughout the house. If they’re not well sealed, tightly affixed to the AC unit and efficiently arranged, they can be the phantom culprits on your high energy bill.
“Ducts can be big energy wasters, especially when they run through areas that are not heated or cooled. That’s your attic or a crawl space; sometimes they’ll even run through a garage,” says Doug Anderson, a home energy expert with Energy Star.
A duct problem “can throw off the whole heating and cooling balance in your home.”
Cooling your attic via leaky ducts just doesn't make sense (Image: EPA)
So let’s take this step by step. If you suspect you’ve got leaks, you’ll want to get the right supplies in place, take a look behind the scenes of your home HVAC, and then seal up the weak spots, or hire a professional to do the job.
Step One
Get supplies. But don’t use duct tape. Despite its name, duct tape is ineffective, especially if it’s the cloth-back matte gray type. In a hot attic, this stuff just dries up and falls off. The shiny foil or metal tape is better, and works adequately well on flexible ducts. The best stuff to seal up air leaks on solid duct work and in some cases on flexible ducts, is mastic, a goo that you can get at the local hardware store.
You’ll also need a) a flashlight and b) an incense stick and c) plastic ties intended to strap flexible duct together.
Step Two
Inspect it. Peer into your attic, crawl space or the basement ceiling where your ductwork resides. Remember when the kid in Home Alone saw the mighty furnace huffing at him in the basement? This won’t be that scary. But it can help you find the answer to your horrifying electrical bills. According to Energy Star protocol, you should climb into the entrance to your attic, if that’s where the ducts are, but not go any (or much) farther than the threshold. Turn on the light or shine your flashlight around to get the lay of the land. Look for twisted, smashed or disengaged ductwork. Look for gaps and cracks.
Step Three
Get systematic (about finding the leaks). Anderson says that he can’t in good conscience recommend that homeowners crawl around in the attic and do their own repairs. Some folks just aren’t that handy and could make matters worse, and there’s the danger of stepping through the ceiling…. At the same time, we know that many of you will do your own work. So here are some tips: Don’t just crawl around empty handed. Use a burning incense stick to detect drafts. The thin smoke line will help you spot air flow. If you want to get more aggressive, get some theatrical smokes and put it near an air return or at the air blower. Then watch the ducts to see where this nontoxic smoke escapes. Be careful not to trip on electrical wiring or tangle with the fiberglass insulation.
Step Four
Fix it. (Or skip to Step Five.) Again, use mastic or metal tape to seal up cracks and gaps. For big gaps, use drywall netting and mastic. (If you don’t know what drywall netting is or where to get it, proceed to Step Five.) If you’ve got a length of ductwork that has been ripped or crushed, you may be able to replace that entire section. Measure the damaged segment carefully; you don’t want to come up short. Remember too that not all ductwork has the same circumference. Take the damaged piece to the hardware store to match it to a new section. Install the replacement section using mastic, metal tape and the plastic closure ties you will get when you buy the duct work. See Energy Star website for more details on fixing your own ducts.
Step Five
Hire someone. There are as many reasons to hire someone to make leak repairs as there probably are spider webs in the far corners of your duct system. Your attic may be vast, or difficult to navigate. If your ducts are in a crawl space, you could have mold (and there are solutions for mitigating mold at the same time you get the ducts fixed) that you shouldn’t touch. Some more really good reasons to hire professionals: You may have system problems that go beyond leaky ducts, such as a loss of coolant in the system. They can handle that on the spot. Many HVAC experts can also check your blower, AC condensation unit and so on, to make sure the entire system is working well. Anderson recommends yearly checkups for your AC and heating systems (one in the spring and one in the fall). These can help head off problems, and while the experts are there you can ask them to run a check for leaky ducts. The cost for this should be moderate, and you will recoup the expense eventually on your electricity bills.
“If they just sealed up a few leaks, they might charge 200-300 bucks to do that and you’ll recoup that money in two to three years,” Anderson guesstimates.
The pros also can do a “duct blaster” test that pressurizes the system, allowing them to better check for leaks, Anderson said. They’ve also got the cool tools (that you can’t afford) such as infrared cameras or “smoke pencils” that can pinpoint all the escaping hot or cool air in your attic, crawl space or even the walls, where duct work is sometimes found.
They’ve got other tricks in their tool chest. Some may cost you a bit, but they can be effective. You’ve probably heard of the door blower test in which HVAC inspectors pressurize the entire house to check for leaks everywhere from the attic to the basement and along windows and doors. These can be pricey though.
Anderson suggests checking with your local utility to see what they offer. Some will run an efficiency check (though not a door blower test) on your house for very little, or in some instances, for free.
While these checks might seem like extra expense, they can pay off in unexpected ways, uncovering the mystery of why one room fails to get cool, or prolonging the life of an AC unit.
“Having somebody take a look at the system can be a good idea,” Anderson says, “and it can be a much cheaper fix than getting a whole new system.”
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