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Dual Zone HVAC Vs Two Units

If you have ever found yourself locked in a thermostat problem, you probably already know the need for a having a reliable HVAC system. Aside from providing more granular control over the various parts of the house, a good HVAC system also enhances the home’s energy efficiency.

Not to forget the added bonus that comes with maintaining proper temperatures throughout the house; you will be cutting down a substantial part of your home’s energy bills, especially when the current HVAC has a tendency to push too hard when it is not needed.

Dual Zone HVAC Vs Two Units: A Breakdown

Today, there are a couple of two approaches when it comes to upgrading or installing a home’s control system; the HVAC zoning system, and the Dual-system. In this article, we will be breaking down the pros and cons of both approaches to determine the best option for your home.

HVAC Zoning Explained

On a basic level, an HVAC zoning system is composed of a series of dampers connected to the home’s central HVAC unit that gives separate control over specific air dust going into various zones/parts of the house. There are two types of dampers; automatic dampers and manual dampers. That said, manual dampers have been largely substituted by their more advanced counterparts, so that’s going to be our main focus in this article.

With the automatic system, there’s a control panel in each zone that determines how much the dampers can open or close in that particular zone. This, in turn, adjusts the amount of heating or cooling that zone receives.

A standard HVAC zoning system can feature as few as two zones (as in lower and upper floor setup) to as many rooms as the house has for maximum control. In most cases, though, a maximum of four zones is normally the ideal amount for a 2-bedroom, 2-story home, i.e. one zone each for the bedrooms and lower and upper floors.

Pros of HVAC Zoning

Budget-Friendly and Lower Maintenance Cost

The fact that you’ll be buying one HVAC unit for the entire house means that there’s an instant benefit in the lower upfront cost of a zoning system, especially in comparison to a two-system approach. In other words, you’ll only need to worry about one HVAC system, which means the overall maintenance cost will be much simpler and less expensive.

Centralized Controls

The fact that each HVAC system connects back to a single HVAC unit means that there can be multiplied control layers integrated with centralized master control. This is usually helpful for situations such as parental controls, where the thermostat in a bedroom zone can be constrained by a range set by the master control panel.

Great Balance of Thermal Capacity

HVAC units are equipped with rated thermal capacity, which is the metric that determines the amount of heating or cooling that particular unit is able to deliver into a given area. Therefore, with just one VAC system, you won’t have to worry about calculating the separate thermal capacities of the zones covered by two different systems.

Downsides to HVAC Zoning

Just One Setting at a Time

When you have just one HVAC unit in an entire house, it means there can only be one set in operation at a time. For instance, you will not be able to set a basement to heating while the other floors are set to cool.

No Redundancy

When you have just one HVAC system in the whole house means that in the event that it breaks down, you will have no backup until the unit is fixed.

Loss of Efficiency

Based on the setup and location of your HVAC system, there can be some efficiency loss when channeling heating or cooling to zones that are rather far away from the HVAC unit due to the length of the ducts that have been used in the installation.

When you have just one HVAC system in the whole house means that in the event that it breaks down, you will have no backup until the unit is fixed.

Dual-Zone HVAC Explained

As the name suggests, a dual/two-system HVAC setup is where a house has two separate HVAC systems for two major subdivisions, for instance, two floors.

Pros of a Two-Zoned HVAC System

There are many advantages that come along with a dual-zoned HVAC system, especially for homes with multiple stories, or those homes with wide areas and multiple rooms.

Customizable Temperature settings

This is probably one of the major highlights associated with a two-zoned system. The ability to completely control the temperature in various areas of the home is an experience every homeowner would greatly appreciate. No more struggles dealing with the thermostat.

Lower Energy Bills

The cost for energy bills will be considerably lower since there will be only one HVAC installed, as opposed to having two or more air conditioning units. The dual-zoned system also makes use of variable speed motors, which reduces the cost by about 30% of the average energy cost.

Variable speed is particularly important when it comes to saving energy. It allows the system to utilize only the amount of energy that it requires to achieve a certain temperature.

Lesser Cost for Maintenance

With a dual-zoned control, the HVAC system will not be working strenuously as in the case of regular HVAC systems. This is because the routing of cool or hot air will be going to open systems.

Downsides to Two-HVAC System

Higher installation and Maintenance Costs

As you could have guessed, installing a dual-zone HVAC system is likely to be expensive, probably as twice expensive as a single-zoned HVAC setup. Maintenance costs will also be similarly expensive, as you will be having multiple systems to maintain and sometimes repair over the years.

Potential Increase in Energy Cost

Although each HVAC unit in a dual-zoned system can be smaller than an HVAC zoning system, the two HVAC units will most likely consume more energy than the single larger unit, especially when both have the same total thermal capacity.


It’s important to note that the two climate control approaches discussed in this article cover only the basics. There are many more factors to take into account to determine the most suitable HVAC system for your home. Having said that, we strongly suggest that you consult a professional to help take a proper look at your home and help decide on the right HVAC setup that is in line with your heating or cooling needs.