Zoning Your HVAC System: When It Makes Sense!

hvac zoning system

Should You Get in the Zone?

A zoned HVAC (Heating, Ventilation and Air Conditioning) system allows you to set different temperatures for different parts of your home. There are definitely some amazing advantages to an hvac zoning system, not the least of which is a lower utility bill. However, zoning isn’t for everyone. There are a lot of variables that must align for an hvac zoning system to make sense not only financially, but to ensure you can deliver optimum comfort throughout the home.

If you’re thinking of installing a zoned HVAC system, or especially if you are contemplating trying to zone an existing single zone HVAC system, you need to consider:

  • What an HVAC zoning system is
  • The advantages of an hvac zoning system
  • Do you have adequate ductwork and equipment to add an HVAC zoning system to your home
  • Is an HVAC zoning system practical for your type of home
  • What type of system is best
  • Consulting an HVAC technician to help you decide which solution is best for your situation

Let’s explore how you might get in the zone.

What Is an HVAC Zoning System?

A standard HVAC system controls the temperature of an entire house. Which is fine if you have a small house on a single level. 

Even then, if your thermostat is located in a relatively large living room, you may find that a small bedroom with a closed door becomes uncomfortably hot (or cold in the case of air conditioning). That is because the thermostat is responding to the temperature in the larger room, which means the smaller room may stay hotter or colder than the living room. 

The only way to remedy this situation is to close the register in the smaller room so heated (or cooled) air stops circulating. This is only a partial remedy, however, because if conditioned air is not circulating in the room, over time the temperature may get uncomfortable.

If this is a chronic issue, the solution is to zone your HVAC system, if it is economically and physically possible.

An HVAC zoning system separates areas in your home that are individually heated and or cooled at desired temperatures. Typically, a standard HVAC system can have as many as four zones. Mini-split systems can have up to eight zones. 

Zones are controlled by a zone board and air temperature sensors open and close dampers to allow conditioned air into the zones. Each zone is separately controlled by individual thermostats, either manually or automatically at a predetermined time and/or triggered by a set temperature level (e.g., heat comes on when temperature falls below 65 degrees). That means you would have four or more separate controls in different areas of your home specifically controlling the desired temperatures in each area. 

Each zone can be set based on personal preferences of individual family members who are in the area the most or the room usage or environmental conditions (a north facing bedroom may get colder than a south facing bedroom). An HVAC zoning system can keep an upstairs cool on hotter days without freezing the downstairs; conversely, it can keep the downstairs warm on cold days without making people upstairs sweat.

Let’s clear up a common misconception – a single HVAC system can not be zoned to heat one area while cooling another. That is not possible. You can only accomplish this if you have two separate systems. 

HVAC Zoning System Advantages

The obvious advantage to an HVAC zoning system is comfort. Everybody in each zone gets to set the temperature most comfortable for the room they are in. 

A zoned system also optimizes energy usage, eliminating wasteful conditioning of seldom-used areas, such as guest bedrooms or rooms used primarily for storage.  According to the U.S. Department of Energy, heating your home is the biggest expense in your home, accounting for 42 percent of your utility bill. A zoned system with programmable thermostats could save you up to 30 percent on your energy bill.

Less energy use is also better for the environment. Fossil fuels account for the majority of electrical generation in this country. According to EnergySage, home heating accounts for 32 percent of electrical usage that results in fossil fuel greenhouse gas emissions. While you may be only one individual homeowner, collectively more efficient HVAC systems can help reduce national greenhouse gas emissions.

Can You Zone a Non-Zoned HVAC System?

The best time to add an HVAC zoning system to your house is during construction. If you’re not building a house or doing a retrofit, you have to work with what you have. There are two important considerations as to whether or not you can zone an existing single-zone HVAC system.

  • Whether the equipment is two staged or Modulating
  • Whether the ductwork is properly sized, distributed and connected

Two Stages or Modulating

In order for an HVAC zoning system to work with existing HVAC equipment that is not zoned, it must have at least two-stage (high and low) equipment or modulating (Multi Stages). Single-stage equipment cannot be zoned.

Here is why: 

Single staged equipment has only one level of heat or cold output to condition all the living spaces. If you try to zone that equipment, the system cannot ramp itself down sufficiently to provide the lower BTU’s (British Thermal Units) or CFM (Cubic Feet per Minute) of airflow needed to condition smaller spaces. 

This can cause some major problems with the system overheating or freezing up, which will cause premature failure or short cycling of the equipment. In addition, you will still be paying for 100 percent of the systems capacity on a single stage unit, so there will be no utility savings even if there is a thermostat in another zone with lower settings.

In contrast, two stage equipment can work at 60 percent capacity. So when you are using only one zone, you are saving 40 percent on your gas and electric usage. When you have both zones on, then the system ramps back up to 100 percent capacity to accommodate the entire living space. A modulating system used for homes with three zones or more can vary between 40 to 100 percent of output. 

Don’t have two staged equipment? Then you’ll have to consider the age of your existing HVAC system and whether the potential pay-off in more efficient energy expenditures justifies the cost of replacing the equipment. An HVAC professional can help you make this assessment.


Ductwork is another key consideration. Your ductwork comprises the tubes that distribute conditioned air throughout your house. For the most part ductwork is concealed behind walls and underneath floors; ductwork is only readily accessible in crawl spaces, basements and exposed attic ceilings. 

Ductwork must be sized correctly to accommodate the correct CFM to each zone in order to achieve the desired temperature. Furthermore, ductwork must also be designed correctly to shut off or open correctly when each zone is calling for heat or cooling. 

If you don’t have correctly sized and connected ductwork, you are looking at possible considerable expense to replace it. Again, an HVAC professional can help you determine if the potential benefits justify the cost.

How Do I Know If an HVAC zoning system Is Right for My Home?

Most people think a zone HVAC system can help them reduce their utility bills. That is usually the case, but certain types of homes and living situations benefit more than others.

Multi-story homes almost always benefit from zone systems. Heat rises and cold air falls, which means upper floors have different conditioning needs than lower floors. So if your thermostat is upstairs and you turn the heat on, the temperature is achieved sooner upstairs than downstairs, meaning you may not achieve the same temperature downstairs before the heat shuts off. 

Even single story ranch homes can benefit if there is a part of the house that is rarely used. You would have to weigh whether the cost to zone your existing HVAC system is worth it as opposed to just shutting the vents in that area.

Of course, if your existing system requires resizing ductwork or replacing single stage equipment with two stage equipment, just closing the vents may be the more affordable option. Another alternative is to add another system, such as a mini-split, that doesn’t require installing ductwork. Consult your HVAC professional whether a two system HVAC makes sense for your budget, room usage and comfort goals.

Needless to say, if you are building a new home or doing a whole-house renovation, zoning is almost always the way to go.

Finding an HVAC Contractor

As Donna Boyle Schwarz writes in Bob Villa, “Adding a zoned heating system to an existing home is a fairly complex project and typically requires the use of a professional installer.” 

Ongaro and Sons technicians are trained for all residential makes and models of HVAC systems. We are happy to advise you on what can work best for your heating and cooling needs in your home, whether it is to zone an existing HVAC system or install a new system. And we back it up with a 10 year parts and labor warranty.

All our work is guaranteed and performed at the price we quote. If you are looking to get into another zone, contact Ongaro and Sons for a consultation and free estimate.