Ductwork to and from the heating source should be sealed to maximize the units' effectiveness and maintain a healthy balance within a home's conditioned air spaces. Duct mastic, caulk and tape each has its own application.
It's far from glamorous and there's no flashy end result, but there is a sense of accomplishment when your heating and air conditioning bills improve, the furnace and air conditioner work more efficiently and you breathe healthier once those darn ducts are sealed properly.
"First and foremost is maintaining the furnace's filters," said Mark Callender, regional manager for UGI HVAC of Lancaster and Harrisburg. "They are the lungs of the system." Standard disposable fiberglass filters are only 7 percent efficient and should be checked bi-monthly; an upgraded pleated filter is between 30 and 40 percent efficient and should be checked monthly. Duct leakage, said Callender, reduces a system's efficiency by 25 percent.
Duct leaks allow conditioned air, whether heated or cooled, to escape or unconditioned air to slip in. The problem snowballs and can cause a pressure imbalance of the whole house, possibly generating leakage though the building shell, according to oikos.com. Ducts running through unconditioned attics, crawlspaces, garages and basements are common sources of leaks.
Any place where air can get into the system should be sealed. Galvanized metal ductwork, which typically has air gaps at the joints, can be sealed with duct mastic. This is a gray substance, of about the same consistency as joint compound, which is troweled or brushed on, or applied with a gloved hand. However it's applied, it's a messy job.
Fiberglass duct board is used to span joists to create supply or return runs. The board's foil backing is wider than the insulated part so it can overlap whatever it is butting up against, and is secured with metal foil tape. Flexible duct is the round accordion-fold material that completes runs.
There is also duct caulk and metal foil tape. "Check where the boots connect to the runs and where the ducts run to the registers," Callender said, as well as the filter door and filter rack. You'll still need to be able to access the filter door, he stressed, so use foil tape or duct tape that can be removed.
Mastic is not a mechanical fastener, so sheet-metal screws are still needed to join the pieces. Fiberglass drywall mesh can be used under the mastic to span large openings.
After you've sealed everywhere possible, Callender recommended installing a programmable thermostat, which claims to offer a 30 percent savings when the setback feature is used, to improve efficiency. The savings is realized, Callender said, if the thermostat is programmed up to 10 degrees lower during hours when you're sleeping or the house is vacant during the workday. For every 1 degree of setback, there is a 2 percent energy usage savings. Proper installation is critical to avoid damage to the unit or nearby components. When in doubt, check with a licensed professional.
An energy audit can be done by UGI servicepeople, as well as other HVAC contractors. Special equipment is used to determine insulation values and areas where the heating and air conditioning systems, as well as the house, are leaking. "We pinpoint the areas of concern," he said. The homeowner can choose to do the work himself. Electric companies often offer rebates to homeowners for energy audits or when energy-saving work is completed.