AC System Ducts

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How Conditioned Air is Distributed:

Homes with central heating and air-conditioning systems rely on ductwork to distribute warmed or cooled air throughout the house.


Today’s ductwork consists of insulated flexible tubes that snake across the attic floor or under the house. Unfortunately, heating ducts are out of sight and therefore out of mind. Homeowners wouldn’t put up with leaking water pipes. But ductwork — carrying air instead of water — can leak for years, without anyone knowing it.

Ducts can leak for reasons as simple as a protruding nail in the attic that snags and tears the duct when it’s being installed. Then, too, joints and junctions where two pieces of duct come together may separate over time — especially if that pesky duct tape we talked about in out last blog was used to join them.

Some contractors even forget to attach ductwork together or to connect it to the vent in the wall. As a result, an open duct wastefully pumps conditioned air into the attic or under the house, while the room it is supposed to serve never gets comfortable.

Problems also occur when ducts are blocked or kinked. Just as a pinched garden hose cuts down the flow of water, a kinked duct drastically reduces the flow of air. Kinking can happen when ducts are forced into tight places under the floor or in the attic. Make sure ducts are properly supported, don’t sag, twist or bend unnecessarily, and they have no gaps or breaks.


Design is important as well. Improperly designed systems may have ducts that are too small for the amount of air they are supposed to carry, or a duct that is too large in one room may siphon off conditioned air that should be going to another part of the house. The air conditioner or heater may be either undersized or too large for the duct system, providing too little or much more pressure than the system was designed to handle.

If its duct system is poorly designed or poorly installed, a house will waste energy, no matter how well insulated it may be, or how efficient its furnace and air conditioner are. That’s why it’s a good idea to have your duct system examined for leaks, blockages, and just poor design. You may be amazed at the monetary savings and the dramatic increase in comfort.