How Furnace Zoning Works (And Everything Else You Need to Know About Zoning)

February 18, 2016

Do you have hot and cold spots in your home? You may have heard that zoning can help.

And now you’re wondering “How does zoning work?” and “What do I need to get zoning?”.

Well, have no fear, we’re going to answer all those questions and more. But first, we think it’s important to understand the problem causing your uneven temperatures...

The problem: uneven temperatures

When your heating system was first installed in your home (either when the home was built or when heat was added later), the installers sized your system and the ducts so that you got a nice, even temperature throughout your home.

They did this with some complicated calculations that take into account things like:

  • Insulation levels
  • Size of room
  • Location and number of windows in rooms
  • Ceiling heights
  • Direction the room is facing, 
  • etc. 

In general, that means large rooms get more and/or larger ducts with more vents while smaller rooms get fewer and smaller ducts. When done right, your home is a nice, even temperature.

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Ideally, your entire home stays the same temperature. 

But it’s not always perfect. For example, during parts of the year, the sun might heat up one side of your home more, raising the temperature on that side. If your thermostat is on the other side of the home, your heating system will leave the sunny side of your home quite warm.

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If your thermostat is on the warmer side, the thermostat will register the warmer temp and not turn on the furnace as often, leaving rooms on the opposite end of the home chilly.

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So now that you understand what causes uneven temperatures in your home, let’s look at how zoning helps…

How zoning a furnace system works

A zoned system contains 4 main components:

  • Control panel—The control panel is the brain of the operation. It’s installed at your furnace and reads the different thermostats and tells the dampers to open or close.
  • Duct dampers—Dampers are the valves in your ducts that open and close to let in more or less air to certain areas of your home.
  • Zone thermostats—Each zone gets a thermostat. The thermostat reads the temperature of the zone and talks to the control panel which then opens or closes the dampers to that zone.
  • Multi-stage furnaces and variable-speed blowers—When there is less heat needed, this type of furnace can adjust to a lower setting.

To see how this works, let’s look at an example:

Say you have 2 zones in your home. Zone 1 is colder than zone 2.

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Your furnace would kick on and the dampers in the ducts would adjust so that more air is flowing to zone 1.

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If zone 2 reached its set point before zone 1, the control panel will tell the damper for zone 2 almost completely close and the furnace to shift to a lower setting. Basically, you’ll then only really be heating zone 1.

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Sounds pretty great, huh?

But wait! That’s not all…

You can also use zoning to keep different parts of your home at different temperatures.

For example, maybe you want to keep your bedrooms warmer at night, say at 70° F, while you let the rest of your home get down to around 65° F.

The same principles still apply. Since your bedrooms need more heat, the dampers will direct more heat to that zone. And your furnace will adjust its speed and heat output, as needed.

Important zoning considerations

All this sounds great, right? Well, there are several things you should know about zoning before jumping in:

Zoning shouldn’t be used to correct building problems
Sometimes one side of a home is always hot or cold because that side has no (or very little) insulation or because it has major air leaks. In those cases, it’s better to fix the insulation and air leak problems before thinking about zoning.

Zoning requires modulating equipment
You need a furnace that can adjust its heating output and airflow. You need a multi-stage furnace and/or a variable-speed blower.

Zoning requires new ductwork
Your ductwork will need to be reconfigured to work correctly. Often, this means installing brand new ductwork in most of the home.

Some notes about other types of “zoning”

A zoned system is what we’ve described above—a single heating and air conditioning system controlled by multiple thermostats in multiple zones. But people often use the word “zoning” to refer to several different heating and cooling setups.

To help clear up some possible confusion, here are some other things people mean when they say “zoning”:

Multiple-systems
Instead of having 1 larger heating and AC system for the whole home, you have 2 (or more) smaller systems. This is common in 2-story homes where you have 1 system that heats the upstairs rooms while the other one heats downstairs.

Using room sensors for faux-zoning
Another way to achieve more comfortable temperatures is to use temperature sensors to give your furnace more data points to use. The temperature sensors are placed in different parts of your home.

Your system can then use an average temperature from these different sensors to help it better know when to turn on and when to turn off.

This isn’t technically zoning because you’re not really changing airflow to different parts of your home.

Smart vents
Some recent smart vents, like this one and this one, say they can give you the benefits of a zoned system at a fraction of the cost.

But do they work as well? Likely not. You see, they change how much air comes out of your vents, but don’t change what your furnace is trying to do. This can lead to problems like increased duct leakage, higher energy bills and a cracked heat exchanger.

Here’s a great article for more info on the problems these smart vents can cause. 

Want more information?

Think that a zoned furnace system might work for your home? You can setup an appointment with one of our comfort specialists to get more information.

Santa Fe Air Conditioning and Heating serves the Kansas City area. For more information, contact us online