Can I save money by closing off registers in unused rooms?
It’s not that simple. Closing off registers may in fact increase your fuel bill and at the same time shorten the life of your furnace and air conditioner. Here’s the rub, an HVAC system is designed to condition a certain volume of air. If you close off registers you restrict the amount of air that can travel through your system. What happens is the furnace and air conditioner produce more heat or in the summer remove more heat than the furnace or air conditioner can handle with reduced air flow. Air flow is measures in CFM (cubic feet per minute). A 2 ton system generally will require 800 CFM to operate as designed. If you close off one register you may be fine, but if you cut all of them back you may reduce the air flow causing the air conditioner coil to freeze up or the furnace to short cycle. Both of these things are very bad for both your fuel bill and the health of your system. For example if you furnace short cycles it put undue heat on the heat exchanger and could cause it to crack or otherwise fail. More noticeable is the increase in your fuel cost. Short cycling means you are heating the furnace area very hot but the heat isn’t getting distributed to the rest of the house including the thermostat which will turn it off. It’s like having a dirty filter, another cause of reduced air flow. A properly installed HVAC system will have volume dampers on each run off the main truck line. They should be balanced to provide conditioned air to each room based on the size of the room. If you want to remove rooms form the system you need to have an automatic damper system (zoning) installed with a bypass damper or other means of reducing the furnace output when some zones are closed. The idea of zoning is to be able to heat or cool different rooms in your house at different temperatures. So if you want to close off a room and turn the temperature way down, you can do it efficiently without worry of damaging your system. In addition you will save energy using this method. Zoning in residential homes is becoming more and more popular. Newer furnaces have modulating gas valves and variable speed blower motors allowing the ability of the home owner to change the capacity of the HVAC system on the fly. With new technology thermostats, damper motors and damper controls it is very affordable to add zoning to the typical house. If you have questions about zoning, how it works, what it cost or if it’s the right choice for you contact LRF Maintenance, LLC in Pickerington, OH or send me email Larry@lrfmaintenance.com and I will get right back to you.
This was written by Larry Ferris from LRF Maintenance, LLC, Pickerington, Ohio comments concerning the content here can be directed to him, Larry@lrfmaintenance.com.