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HVAC Zoning Vs. Two Systems

Anyone who has ever found themselves locked in a thermostat battle with other members of the household knows the importance of having a good HVAC system. Not only does it give more granular control over different parts of the house, but a great HVAC system also boosts the home’s energy efficiency.

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Of course, there is also the added bonus of cutting down a significant part of the home’s energy bills by maintaining a proper temperature throughout the house, especially when the current HVAC has a tendency to push too hard when it is not needed. 

Nowadays, there are two popular approaches when it comes to installing or upgrading a home’s climate control system—there is the “HVAC zoning” approach and there is the “two-system” approach. And in this article, we will be breaking down the pros and cons of both methods to help you choose the best option for your home. 

What is HVAC Zoning?

An HVAC zoning system is made up of a series of dampers connected to the home’s central HVAC unit that allows for separate control over specific air ducts going into specific “zones” of the house.

These dampers are further separated into two types—manual dampers and automatic dampers—but manual dampers have largely been superseded by their more advanced counterparts, so that will be the focus for this article. 

In this system, each zone is given its own panel that controls how much the dampers open or close in that zone, thereby adjusting the amount of cooling or heating that zone receives.

A typical HVAC zoning system can have as little as two zones (as in an upper and lower floor setup) to as many rooms as the house has for maximum control. For most households, though, four zones is probably the ideal amount for a 2-bedroom, 2-story home—one zone each for the bedrooms and the upper and lower floors.

Pros of HVAC Zoning

Cheaper purchasing and maintenance cost

Since you will only be buying one HVAC unit for the entire house, there is an immediate benefit in the lower upfront cost of a zoning system compared to a two-system approach. Having only one HVAC system to worry about also means that maintenance is much simpler and less expensive. 

Thermal capacity balance

Every HVAC unit has its own rated thermal capacity, which is the metric that dictates the amount of cooling or heating it is able to push into an area. Having only one system installed in your home means you don’t need to worry about having to calculate the separate thermal capacities of the areas covered by two different systems. 

Centralized controls

Since every zone in the HVAC system connects back to a single HVAC unit, there can be multiple control layers set up with a centralized master control. This is useful for situations like parental controls, where the thermostat in a bedroom zone can be limited by a range set by the master control panel.

Cons of HVAC Zoning

Only one setting at a time

Having only one HVAC unit in the whole house means that there can only be one setting in place at a time. In other words, a basement cannot be set to heating while the other floors are set to cooling, among other similar situations. 

Efficiency loss

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

No redundancy

Having only one HVAC system in the entire home will mean that, if it breaks down, you will have no backup until it’s repaired.

What is a Two-System HVAC?

A Two-System HVAC setup is exactly as its name suggests: a house with two separate HVAC systems for two major subdivisions, such as two floors. 

With what we already know about the benefits and drawbacks of an HVAC zoning system, you can probably figure out what the pros and cons are for this approach; however, we will still lay them out for you in detail below. 

Pros of Two HVAC Systems

Redundancy

Arguably the biggest benefit of having two HVAC systems is the redundancy of having an extra HVAC system all set up in case one of the units breaks down. 

This is especially important for homes in very cold areas—you do not want to find yourself in the dead of winter with a broken heater for days, if not weeks on end as you wait for a repair. 

Independent controls

With two separate HVAC systems, the areas covered by each system can be heated or cooled on its own, providing a different form of granular control that isn’t possible with a zoned single system. 

Better efficiency per system

Because of the shorter duct systems that are required to channel two HVAC systems to two separate areas, each HVAC unit can run more efficiently than a single unit doing the same across a larger area. 

Cons of Two HVAC Systems

More expensive to install and maintain

For obvious reasons, purchasing two HVAC systems will be around twice as expensive as a single zoned HVAC setup. Maintenance will also be similarly expensive, as you will find yourself with multiple systems to both maintain and repair over the years. 

Higher potential energy cost

Even though each HVAC unit in a two-system setup can be smaller than an HVAC zoning system, the two HVAC units will always consume more energy than the single larger unit when both have the same total thermal capacity. This is just a matter of simple physics and is part of the cost of having two separate systems.

Wrap-Up

Everything we’ve discussed about these two climate control methods in this article only covers the very basics. There are many more variables to take into account when choosing an HVAC system for your home, from the setup of the air ducts to the differences between specific HVAC units. 

Knowing this, we strongly recommend consulting with a professional contractor to take a proper look at your home to help you choose an HVAC system that is in line with your cooling and heating needs. 

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