What is an HVAC Zoning System? (And Why It Works)

A typical call goes like this: I ask, “Do you have hot and cold spots in your house?” Nine times out of ten, the answer is, “Yes.” Their two-story home is too hot upstairs in the summertime, or it’s too cold downstairs.

Hot and cold spots can make your house seem like its HVAC system isn’t up to par. A hot bedroom may be hindering your sleep. A frigid basement turns it into an area where no one wants to venture for long.

Walk around. Maybe you have vents in a room that nobody uses. The room with large, beautiful windows is either too cold or too hot; glass - especially if it’s single-paned - leaks too much heat in the winter and cool in the summer.

Maybe it’s time to rethink what your comfort level should be in every room, not just the rooms you spend the most time in.

If this feels familiar, your home is not zoned properly. Zoning can solve a myriad of HVAC concerns. This article explores what is meant by zoning, how it can be done, why it’s effective, and why it might or might not be the solution you’re comfortable with.

We’ll talk about cheap zoning options as well as some more expensive ones, including a primer on ductless mini-splits.

Zoning may even provide a resolution to those neverending thermostat battles.

What Is HVAC Zoning?

The word “zoning” is used in more than one way in the context of HVAC.

Larger houses are often zoned. They typically have one thermostat downstairs and one upstairs so you can control the conditions in different parts of the house.

You might also have two HVAC systems controlling different parts of your home. That is also zoning.

The third kind of “zoning” is a single HVAC system that has a main trunk (the part of the ductwork that is closest to the furnace blower), with multiple runs. We’ll talk about this version in detail below.

You’ll get the most out of HVAC zoning if you have one or more of the following:

A multi-story home
A basement, either finished or unfinished
A living space in the attic
High ceilings
A room over your garage
A sunroom
Several large windows
A large floor plan with one or more wings

HVAC Zoning Cheaply

To start with, let’s consider an unzoned home. Most homes have one HVAC system with one thermostat, which is usually located on the first floor. When the thermostat calls for heating or cooling, the equipment heats or cools to satisfy the thermostat in that spot. The rest of the home can be 1,000 degrees, or 20 below zero, and the thermostat doesn’t know.

You can manually close some dampers. Sometimes manual dampers are located on the trunk duct in the basement, and you can just close them (though it’s best not to close them all the way; static pressure can be a concern) to push more air through the open one. That change in the airflow can help balance the temperature.

Or you can try closing off air vents. It’s up to you to experiment which vents are the most and least effective.

Your system might need some TLC to help it run better. Dirty filters can restrict airflow in the HVAC. Changing your filters regularly is better for the indoor air quality, and helps your HVAC circulate air better.

A dirty furnace or AC/heat pump coils also heat and cool inadequately. Cleaning them is beneficial.
An inspection of your ductwork is always an option. If it leaks, it should be repaired. Some of it might be improperly sized, with too little air going to parts of your home.
Amending the ductwork might do wonders, though it may require a visit from an HVAC contractor to plan the next move.

If these fixes aren’t sufficient, you may need to invest a bit more money. Those options are below.

Manual Dampers

You can install manual dampers. They require the homeowners’ assistance to open or close.

Manual dampers are usually installed on the trunk duct. You would need to adjust the dampers with the change of the seasons. In the summer, cold air goes down, so you want to try to push more of it upstairs. In the winter, you want to adjust it so that hot air is pushed more downstairs because heat rises.

Pros:

No maintenance is required
It’s a cheaper option than automatic dampers

Cons:

You can’t open or close them remotely
You have to experiment with them to get the optimal airflow
Installation may be required

Automatic Dampers

Automatic dampers are controlled via multiple thermostats. Motors open and close the mechanism inside. Each system can open and close the dampers according to how much heat or cool is required for individual zones. They can do more than just open and close fully; they can pick a position somewhere between the two, depending on how much airflow is called for.

A zoning panel controls up to four zones. If you need more than that, you can add another panel. You have choices on thermostats. Some are just room sensors, which report back to the panel. You can have wired or wireless sensors.

Or you can have a thermostat in individual rooms, and make adjustments from there.

The brains in the zone panel can determine how much air each area is going to need. It thinks, “I’m running this long, and this zone picked up this many degrees. I need to open this damper this much and try to make all of the zones the required temperature at the same time.”

This level of sophistication also has pros and cons:

Pros:

Dampers are operated remotely
Offers a better level of temperature control, thus increasing comfort levels

Cons:

Cost
Maintenance can be costly. Both the thermostats and dampers might need attention
Duct work might be required to get the dampers in place

Some houses were constructed with zoning in mind, but there is no system in place. A house that’s built for zoning is going to have dedicated trunks and ducts. For instance, a trunk duct serves upstairs, a trunk duct serves downstairs, and there’s a separate trunk that serves the master bedroom. All in all, that home has three dampers.

You could then decide to have zones. Most of the installation is already done. Thermostats and a zone panel can be installed, the dampers need to be wired properly, and the system is ready to go.

If the home isn’t pre-built for zoning, you may need to retro-fit a duct system. You would have to isolate the runouts and place dampers on them. For instance, this one goes upstairs, this one’s downstairs. Or you may have to rip the ductwork out and run dedicated trunk lines. This gets messy, and it drives up the cost.

How Much Does HVAC Zoning Cost?

If you want to zone and the cheap options are insufficient, the price is always going to depend on how many zones you want. There would be a minimum of two, up to eight or more. Each zone needs its own thermostat. Dampers have to be wired. A zone panel (or two) needs to be installed.

Two things drive up the price:

Number of zones
Number of dampers

If you have existing ductwork set up for zoning, but there’s no zoning currently, you’re most likely going to spend between $4500 and $7000. That would cover two to four zones.

If there’s no ductwork for zoning, a zoned system would start in the $5000 range up to $8500, depending on your existing ductwork. More ducts will probably be needed.

There’s more labor in the set-up and design than the cost of equipment. It’s labor-intensive. Even when it’s installed, you have to test each zone, set parameters for each zone, and identify the remaining problems. That could take half a day by itself.

Zoning with Ductless Mini-Splits

Yet another zoning option is ductless mini-splits. That will give you the ability to customize temperatures in individual spaces. They typically condition the air in only one room, though you have the option of installing five heads to each unit.

A head is an individual indoor unit that is connected to the outdoor unit and provides cooling or heating to a room or area.

The more heads you have in a system, the more complicated it becomes to properly install, service, and maintain the system.

These systems give you “zone control” over different rooms, or zones, in your home. You can cool one room, heat another, and ignore others.

The biggest factor that affects the cost of a mini-split is the number of “heads” that it has. Below we've listed typical costs. All costs listed include labor and fees.

● A single-zone/one-room heating and cooling solution will range between $3700 and $6000.

● A dual-zone/two-room system will run between $5,500 and $9,000.

● A system that provides heating and cooling for multiple zones of three and up starts at $8,500.

Advantages of a Zoned HVAC

A zoned home allows for an HVAC with better energy efficiency: the system diverts air away from areas that don’t need it. You use less energy to keep your home comfortable.

While it may seem complex, a multi-zone system makes it easy to regulate your energy use and save you money. The U.S. Department of Energy estimates that HVAC system zoning can save homeowners up to 30 percent on a typical heating and cooling bill. Zoning with dampers is more efficient than simply closing the air vents in each room because the dampers provide a better seal.

If you have areas in your home where you rarely go, and don’t feel the need to keep dumping heat or cool into it, sealing it off and creating a zone makes sense from an energy savings and comfort perspective. The heat that you are sending into that area can now be sent to a different area that may need it more.

Next Steps

Yes, we install and repair equipment, but that’s not what we really do. We work with air. We move air. And when we’re moving it, we’re treating it with something. Whether it’s removing or adding humidity, heating, cooling, filtering - it’s all about moving air. All HVAC issues outside of mechanical issues are air-related.

First, you have to understand what the problem is.

If you’re ready to talk to an HVAC representative, you should be aware of all your options. The most important part is finding a solution to your zoning questions that you’re happy with. Our free checklist will provide you with relevant questions to ask any HVAC contractor. By ensuring that the contractor you choose addresses each of these areas, you’ll have peace of mind knowing that whoever you choose, they’ll be prepared to do the job right.