How Leaking Ductwork Costs You Money

air ductLeaky ducts are a common duct design issue that drags down your air conditioner’s energy efficiency. In the Los Angeles area, where every bit of cooling counts, duct leaks aren’t something you can afford to ignore.

Why Duct Leaks Matter

In the average home, the ducts leak between 12 to 30 percent of the air they carry. Duct leaks show up when the sealing between duct joints wears out or when the joints weren’t properly sealed in the first place. The conditioned air produced by the HVAC system’s air handler escapes through these leaks, meaning less of it reaches your rooms. You’ll end up raising or lowering the thermostat temperature to compensate, wasting energy.

Even worse, leaks let in air contaminants such as dust and insulation fibers from the attic and other unfinished spaces the ducts pass through. These contaminants then travel out to your rooms and worsen your indoor air quality. Air leaks can damage your home, too. Cool air hitting the surfaces of a hot attic (or vice versa in winter) creates condensation, which can lead to mold growth and decay in the wood frame of your home.

How to Stop the Waste

Air sealing the ducts in your attic and basement is a good start. Check each joint were two lengths of duct meet and where ducts connect to the floors, walls, and ceiling. Sheet-metal ducts should be tightly fit and connected with sheet metal screws. Use a putty knife or disposable paint brush to apply mastic sealant over the seams. Alternatively, apply heat-safe metal tape. Never use duct tape. Despite its name, duct tape is easily damaged by temperature changes and won’t last long on your ducts.

Any holes in your duct should be patched with metal tape or, for bigger holes, wire mesh and mastic.

It’s possible to reduce your duct leakage to as little as 5 percent; although for this, you’ll benefit from calling in an HVAC technician. A professional can reach the ducts you can’t, choose the optimal sealing material, and identify other duct design issues.