Room Zoning – Keep your House Warm
A frequent complaint from homeowners is “One room in our house is too hot and other rooms are too cold.” Room by room zoning for proper heat can be a tricky balancing act for an HVAC technician.
Let’s start with the basics of how to control temperature in different parts of your home. Most houses have the heater and air conditioner constructed together. In the winter, the heater warms the air and the fan pushes the warm air into the main trunk of ducts. The ducts then conduct heat to the various rooms of the house. In the summer, the air conditioner cools the air which is propelled into the main trunk and then into the ducts for each individual room. Finally, an air return brings the air back to the heater unit for heating before being again pushed through the ducts and into the rooms.
One initial issue for most homes is the “path of least resistance.” It’s like deciding between a chocolate chip cookie and brussel sprouts. Most of the time you choose the path of least resistance—the cookie.
The warmer air being forced upward from the heater might encounter a duct that is 8-feet long dedicated to the lower floors and a duct that is 20-feet long dedicated to the upper floors.
Naturally, the majority of the air will gravitate to the 8-foot long duct.
An excellent solution to achieve room to room zoning for proper heat is to install motorized dampers. These dampers are often installed on each duct and electronically communicate with
the thermostat. For example, based on thermostat readings, the dampers can simultaneously close when the first-floor rooms are at proper temperature, allowing the warm air to move to the upper rooms and bring them to the proper temperature. In a similar manner, the motorized damper can also direct heat to the back of the house or the front of the house, keeping rooms at those locations at the desired temperature.
The motorized dampers feed their information to an electronic control panel that keeps communication going between the heater, thermostat and the dampers. When all systems are working in concert, the thermostat will send out the information for the proper temperature and the control panel will tell which dampers need to be closed and which ones need to be open.
Some furnaces have blowers that are not strong enough to blow the air to the furthest reaches of the house. If not, they need to be replaced. Another issue is that the blowers are too strong. With the motorized dampers doing their work to direct the heat to the right place, the blower that is too powerful can cause whistling and clanging. This can be disconcerting when the owners are trying to sleep or hosting a quiet dinner party. It’s great for telling ghost stories with the lights out on Halloween, but that only happens once a year.
A solution to the noise problem is a weighted bypass damper. When this damper is in place, the air that is being pushed out too strongly will push this damper open slightly and the excess air will simply flow into the return air duct to be rerouted into the system. This will reduce or eliminate the static pressure that would otherwise build up in the ducts and cause the noises.
Finally, thermostats should be placed upstairs and downstairs to regulate the temperatures at both places to the desired heat. Thermostats are available in wireless versions, so they do not
have to be wired into the wall or plugged in. The thermostats should be placed at a location that is not in direct sunlight or next to a heat register.
Hot air rises
Some homeowners may be looking for a simpler, though less precise, solution for room to room zoning for proper heat. Because warm air naturally rises, the rooms on the second floor will usually be warmer than the rooms on the first floor. A single lever can be flipped that will close the damper on the ducts leading to the upper floor. Normally, enough warm air will still rise to the upper floor to keep the rooms warm. The closed damper will cause more of the warm air to be forced into the lower floor to achieve the desired warmth there.
During the summer the damper should be flipped in the opposite direction forcing more cool air upstairs to keep those rooms sufficiently cool. Since cooler air tends to fall, the air for the lower
floors should be adequately cooled by the falling air. How do you know if the damper is open or closed? Usually, the lever will feel firm and snug when the damper has been pushed to open. The lever will feel loose when the damper is open.
By using the dampers, the cold air and hot air will be more efficiently direct to the desired rooms. Not only will the temperatures be closer to the right level, but the furnace won’t have to work as hard to push the air. This should result in a longer life for the furnace and less fuel
needed to run the heater.
A final step for a more efficient system is to look for leaks in the ducts. Each joint where the sheet metal fits into another duct has the possibility of leakage. Perhaps the joints were last sealed years ago and the duct tape has gone slack and no longer fits tightly. This easy fix means the homeowner can locate each joint, place his hand over the joint to see if he feels air escaping, strip off the old duct tape and replace it with new. Two-inch wide tape can usually mean a snug fit and keeps the heated air in the system for maximum efficiency. Each leak might seem small, but the result of multiple leaks sealed can be significant energy savings.
Don’t be a martyr and put up with some rooms in your house being too cold while others are too warm. Using room to room zoning techniques for proper heat can make you comfortable no
matter what room you are in.