Zoned Heating

Zoned heating allows you to heat just the rooms or areas of the home that you want. Whether you heat your home with a boiler, furnace, or electric baseboard units, each can be set up to be individually controlled from different areas of the home.

Electric baseboard is the easiest because, in most cases, each unit has its own thermostat, which is normally located on the wall or on the unit itself. Every room with an electric baseboard unit is a separate heating zone that can be set to whatever temperature the user wants. Of course, with electric rates rising in recent years, some people are turned off (no pun intended) by electric baseboard heat, but, again, you can easily heat only the areas of the home that you are actually using. Also, electric baseboard units require very little maintenance and don’t require an annual clean/service like what is needed for boilers, furnaces, and heat pumps.

Good graphic showing how zoned heating works (photo courtesy of Abe Heating And Cooling)

Boiler systems can be zoned as well and this often consists of separate thermostats in different areas of the home (sometimes one per level) and a single boiler (normally located in the basement). Each thermostat controls its own pump in a return line near the boiler. If the 1^st level’s thermostat calls for heat and the 2^nd level’s thermostat does not, the boiler will still run but only the 1^st level’s pump will operate and only the 1^st level will be heated. When the pumps operate, they allow the flow of hot water through the heating system’s plumbing which is connected to radiators or convectors or radiant piping in flooring. Even if the boiler heats the home’s potable water, the heating system’s piping is separate from the home’s hot potable water. In other words, you are not drinking the same water that goes through the radiators or convectors. Radiators (properly pronounced: RAY’-dee-ate-ers) are the large metallic units (often cast iron) often located below 1 or more exterior windows in each room and convectors are the much shorter cousins which typically line an entire wall along the baseboard. They both give off heat, but one radiates the heat and one convects the heat. Remember the types of heat transfer (radiation, convection, and conduction) from grade school science class? Boiler systems heat water and furnaces heat air. A lot of people interchange these terms, but these two appliances are very different and should not be confused. When a boiler turns off, the flow of heat from a radiator or convector can still occur for hours later as the amount of heat in the water still needs to move to from the water, into the radiator or convector, and then into the air in the room. This heat transfer will slow down and eventually stop once the air and radiator or convector temperatures meet.

Furnaces and heat pumps (both are forced air systems) can also be set up for zoning, although this is much less common and requires a different duct design versus a standard single-zone duct system. To zone using a forced air system, mechanized dampers are installed in the supply ductwork near the furnace or air handler. Each zone has a different system of ducts between the heating system and the area that has its own zone. Using multiple thermostats in the home, each thermostat controls its own damper which opens or closes a little door inside the duct based upon the call for warm or cool air. When you have a central A/C system combined with a furnace, if you have a zoned heating system, you also, therefore, have zoned cooling. Retrofitting zone heating (forced air or hot water) in a current home can be difficult as it depends upon how the original ductwork or plumbing is installed. For a furnace system, there may be a single main supply duct that then splits into runs for the 1^st and 2^nd levels. For a boiler system, main supply and return pipes exist at the boiler and depending upon how these pipes are setup, adding multiple pumps may not be possible or feasible.

A qualified HVAC contractor can evaluate your home’s HVAC system to determine how difficult converting it to a zoned system may be and the costs associated with this modification. Properly installed, a zoned heating system can save money in energy costs and increase interior comfort. After such a system is installed, the key to this efficiency and comfort are based upon proper usage of the thermostats. If all of the thermostats are simply left set at the same temperature all of the time, the benefits of a zoned system are minimal to zero. Programmable thermostats can be used with these systems, and if properly used, can provide the designed benefits of zoned heating.

Central heating systems (furnaces, boilers, and heat pumps) should be professionally serviced annually. During this process, the HVAC professional should check the operation of the dampers or pumps as well as performing the annual maintenance on the actual heating system itself.

Matthew Steger is a Certified Level 1 Infrared Thermographer, an ASHI Certified Inspector (ACI), and an electrical engineer. He can be reached at matthew@thehomeinspectorsnotebook.com. No article, or portion thereof, may be reproduced or copied without prior written consent of Matthew Steger.