Insulating ducts helps hold in conditioned air

Dear Jim: There are a couple of rooms in our house that are always too hot (summer) or too cold (winter). Without installing an expensive zoning system, what can we do to make those rooms more comfortable? – Scott W.

Dear Scott: First, try to determine why those rooms are not staying the same temperature as the rest of the house. Hold a thermometer in the air flow from a register and compare it to the register air in the other comfortable rooms. Also, hold your hand over the register to feel if the air flow is equally strong to that in the other comfortable rooms.

If the register outlet air temperature is warmer (summer) or cooler (winter) than from other rooms, but as forceful, you may need to insulate those ducts. They are likely longer ducts (rooms are farther from the furnace) and may not be insulated from the outside walls or attic.

If you find the air flow is not as strong, make sure the dampers in the ducts leading to those problem rooms are fully open. It would be a good idea to wrap foil duct tape around all the duct joints. In a long duct, this can often make a significant difference in the amount of conditioned (heated or cooled) air that actually gets to the room register.

Partially close the dampers in the ducts leading to the comfortable rooms. This will force more conditioned air to the problem rooms. Don’t close the dampers more than halfway because you don’t want to excessively increase the air flow resistance for the blower.

It is easy to install duct dampers if your existing ductwork does not have them. Another option is to install register covers with adjustable louvers. This is more expensive than installing dampers, but real wood and cast metal registers are attractive. Also try using tapered magnetic register air deflectors to distribute conditioned air more evenly in rooms and magnetic flaps to seal off registers.

If the problems still exist, consider installing booster fans to force more conditioned air to those rooms. These are made in many sizes and configurations to fit almost any duct. Some of these fans use as little as 20 watts of electricity so they are inexpensive to operate.

Whenever the main blower starts, the booster fans also run. They can be wired to be operated from the main wall thermostat. A simpler setup for do-it-yourselfers uses a pressure or sail switch. These switches sense the air flow when the main blower starts and they switch the booster fan on.

Another option is a quiet booster fan that is mounted over the top of the room register and plugged into a wall outlet. It has an adjustable built-in electronic thermostat. It runs only when both the main blower is running and its thermostat calls for more heated or cooled air in that room.

The following companies offer registers and booster fans: Aero-Flo Industries, (219) 393-3555, www.aero-flo.com; American Metal Products, (800) 669-3269, www.americanmetalproducts.com; Deflecto Corp., (800) 428-4328, www.deflecto.com; Field Controls, (252) 522-3031, www.fieldcontrols.com; and Suncourt Manufacturing, (800)999-3267, www.suncourt.com.

Send inquiries to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.