Energy-saving tip: Check your ductwork

Out of sight, out of mind, usually. It's time to give some attention to your air conditioning ductwork.

The ducts are those large flexible plastic or aluminum tubes that are probably criss-crossing your attic. They're cold-air highways: they transport cold air from your air conditioner compressor to specific rooms in your house.

The problem is that, because all they have to do is hold cold air, ducts are not exactly sturdy. It's easy to knock them out of alignment or crush one; all you'd have to do is back into one while installing cable t.v., for instance. And where the tubes join or turn corners, they are typically joined by duct tape (yes! the original use for that ubiquitous substance!). Over time, duct tape dries out, cracks, and leaves gaps.

Wherever there is the slightest crack, hole, or gap, cold air will exit the duct system and start cooling your attic instead of your house. Leaking air conditioner ducts can raise your cooling costs by 20%-40%.

What to do?

• Early in the morning (while it is still livable up there), turn on your air conditioner full force.
• Grab a brightly colored marker or some red tape and go into your attic.
• Do a visual inspection.
• Check both sides of turns--any obvious gaps?
• Are there any areas that aren't insulated?
• Run your hands over your ductwork.
• Feel a breeze or blowing air? You've got a leak.
• Feel a cold or wet spot? There's a leak under the insulation.
• Mark the spots with your marker or red tape.

If the problem is one you think you can fix yourself, don't use duct tape! It will simply dry out over time and crack or peel, and you'll be back where you started.

Instead, use a mastic sealant. It comes in both liquid and tape forms, and you can get it at a building supply store. Mastic sealant will fill cracks and crevices as well as sealing gaps, and it never completely dries, so it keeps its flexibility.

If you call in professional help, insist they fix the spots you've tagged before they try to sell you an entire new air conditioning system.