Photo by Field Controls
This duct booster fan replaces a short section of the existing duct. Notice the small, plastic fan blade for quiet operation.
Q: Our new heat pump isn’t keeping all the rooms in our home comfortable. Someone is always too hot or too cool. How can we even out the temperatures throughout our house?
A: The problem you are experiencing is common, particularly in a two-story home—even with the newest heat-pump systems. Unless you install an expensive zone-control system with multiple thermostats, your heat pump can only respond to the temperature of the room where the wall thermostat is located.
Many factors affect how much heating or cooling is used in a room, impacting the temperature. These can include the number and orientation of the windows, whether the room is on the first or second floor, the activity level in the room, and the length of the duct leading to it.
Differences in the energy efficiency of various rooms can also cause a temperature imbalance. Leaky windows are a particular problem.
One simple way to better distribute cool air throughout rooms is by placing air deflectors over the registers.
You should also check your home’s attic insulation, especially if it is the blown-in type. Insulation can shift over time, leaving some rooms with 2 feet of insulation, while others have only 2 inches. This can have a big effect on room temperature. Even out the insulation as much as possible.
Standard, builder-installed, sheet-metal ductwork often has many leaky spots, so some of the heated or cooled air leaving the heat pump never makes it into your home. The joints between the duct segments are the most common areas that leak. Wrapping all joints in high-quality duct tape may solve most of the problem.
Each room should have a return-air register, particularly bedrooms where doors may be closed at night. Return ducts usually run between the wall studs inside interior walls. Adding them in problem rooms is not difficult for a contractor to do.
Check the ducts near your heat pump. If you see short handles on each one, they are for control dampers inside the ducts. When the handle is parallel to the duct, the damper is fully open. Partially close the dampers in the duct leading to rooms that get too much heating or cooling; that forces more air to the problem rooms.
Don't close the dampers in the room’s floor or wall registers. Typically, they are leaky, so the air flow won’t be reduced much. And, because the ducts inside the walls are probably leaky and you have no access to seal them, conditioned air will be lost inside the exterior walls.
If these methods don’t help, consider installing duct booster fans. These small fans mount inside the ducts to problem rooms and force more conditioned air to them.
The fans are sized to fit standard round and rectangular residential ducts. The simplest models sense when the main blower turns on and automatically run at the same time. Others have built-in thermostats to determine when they run. Let an experienced contractor handle the installation for you. He can wire the fan into your blower switch to turn on with the heat pump.
An easy, do-it-yourself option is to install a register booster fan. This small, rectangular fan mounts over the register cover in the room and plugs into a standard electrical outlet. It uses only about 30 watts of electricity. Some models are adjustable and turn on only when more cooling or heating is needed in that particular room.
Companies that offer duct booster fans include Aero-Flo Industries, (219) 393-3555, and Field Controls, (252) 522-3031.
Companies that offer register booster fans include Air Flow Technology, (800) 458-5540), Suncourt Manufacturing, (800) 999-3267, and Tjernlund, (800) 255-4208.
Air-register deflectors are available from Deflecto Corporation, (800) 428-4328.
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