Over the years, I came across many people who asked me one simple question – “Hey, I have a 2-story building. Should I zone an HVAC system or just buy two different HVAC systems?”.
Two-story homes often face warmer air on the upper floor. This is due to warm air being lighter and flowing upwards. Sun exposure and heat gain from the roof and walls also contribute to the problem. However, we don’t want that for comfort, well-being, and livability. This uneven heating and cooling can put extra strain on a single air conditioner, forcing it to work harder and potentially shortening its lifespan. Because hot air naturally rises, the upper floors are often warmer.
HVAC systems are the main way to counteract natural heating or cooling issues. Whether you use a traditional furnace and air conditioner or a more modern heat pump, the goal is consistent comfort. But what about two-story buildings? You don’t always require multiple HVAC systems to maintain multiple levels. HVAC zoning can direct the required temperature to specific places too. Many homeowners consider multiple HVAC systems to solve temperature imbalances. Using multiple hvac units can provide better control.
In this guide, I’m going into detail about HVAC zoning and two different HVAC systems- which one is perfect for two-story buildings.
What is an HVAC Zoning System?
HVAC zoning is separating your living space into different zones to control the flow and temperature of each zone. This is achieved through modifications to a standard HVAC system.
A zoned system can improve comfort and efficiency.
Central HVAC systems (Trane 2 Ton 17 SEER2 Two-Stage Gas System is a good example) work to achieve the same result for the whole household. In “zoning”, different zones can have different atmospheres. Thermostats are dedicated uniquely to every zone to control heating and air conditioning operation. A whole house system is designed to treat the entire building as one zone.
How Does It Work?
HVAC zoning system has 3 main differences from central HVAC in terms of components:
- Zoning dampers
- Multiple thermostats
- Control panel/Zone controller
Dampers are installed in the ductwork. They open and close based on their settings to regulate the airflow. The central HVAC system unit controls these dampers.
Proper air flow is crucial for efficient HVAC system operation. Multiple thermostats are there to monitor multiple zones. This allows for precise control of each zone’s HVAC system. Maintaining proper air flow ensures even distribution of heated or cooled air.
Read Also: 5 Ways to Increase Airflow in Closed Office
Pros and Cons of HVAC Zoning System
Pros:
- Enhanced comfort by satisfying individual preferences
- Greater energy efficiency from using just enough space for energy
- Elimination of temperature imbalances
- Increased entire home value
- More cost-effective compared to installing multiple systems
Cons:
- High initial cost
- Requires skilled professionals for handling complex HVAC system installation process
- Potential for increased maintenance for the whole HVAC system and its components
- Might need ductwork rework to accommodate zoned HVAC systems
Integrating Two Separate Systems
Two separate HVAC systems can work as two zones in an entire home. It is sometimes also called the dual HVAC or dual zone system.
The dual HVAC system is especially common for two-story buildings. One unit is dedicated to each floor. First floor can have a different settings from the second floor. The floors have separate furnaces, air conditioners, ductwork, and controls of their own. There are two thermostats dedicated to each zone too.
Each HVAC system operates independently to maintain desired temperatures on each floor. In some cases, especially in milder climates, homeowners may opt for two heat pumps instead of a furnace/AC combination for each floor.
Some homeowners prefer to use two systems to achieve optimal comfort. These two systems work independently to provide customized comfort.
Pros and Cons of Dual Unit HVAC Systems
Pros:
- Eliminates temperature imbalances between floors
- If one unit fails, the other can still condition the air
- Ideal for larger homes
Cons:
- The upfront cost of two HVAC system units
- Operating cost of two HVAC system units
- Needs more space for equipment and complex wiring
- Might not have the peak efficiency
- Maintenance cost doubles
Head-to-Head: HVAC Zoning vs. Two Systems
For a homeowner, the choice comes down to a few key factors. Here’s how the two solutions stack up against each other.
HVAC Zoning vs Two Systems: Factors to Consider When Choosing
To summarize, HVAC zoning system creates multiple zones from one central HVAC system (only one system). On the other hand, two different HVAC systems have two separate systems to create two zones. It’s not just a matter of creating zones, there are other factors involved.
If you are unsure of which one to pick, consider these factors:
- Home Size and Layout
Smaller to medium-sized homes, even if they are two-story, benefit more from zoned HVAC system. Larger homes often have layouts that make even air distribution difficult. So, two different HVAC systems work better in this case.
- Budget
HVAC zoning is less expensive because it needs one central HVAC unit. Additional costs are from the extra equipment to create zoning and labor costs. The maintenance cost is also lower. While HVAC zoning requires a smaller initial investment in equipment, including only one air conditioner, the long-term energy savings can help offset the cost of installation.
If budget is less of your concern, you can opt for dual HVAC systems that will give you the most comfort.
- Severity of Temperature Imbalances
HVAC zoning is perfect if you face moderate temperature fluctuations between floors. If you face a significant imbalance (more than 10 degrees), a dual HVAC system will be more effective.
- Comfort Needs
If the family members or residents have a major difference in preference, zoning can still work to some extent. A dual system offers more flexibility in those cases.
- Occupancy Pattern
Spaces within the entire house that are frequently unoccupied greatly benefit from zoning. You can change the activity of the HVAC system based on pattern too. In a dual system, you need to completely shut down a floor’s activity for unoccupied spaces which is not practical in most cases.
- Existing Ductwork
If your existing ductwork can be modified, zoning can save you a lot of cost. Old, leaky, and poorly designed ductwork is not suitable for zoning. It often results in extra cost. So, a dual system is a viable solution for that case.
- Maintenance and Repairs
The maintenance cost of zoning is also lower along with its upfront cost. As the dual system uses two HVAC system units, the maintenance cost and repair costs over time are also almost doubled.
Which One is Perfect for a Two-Story Building?
Considering all the factors, here is a checklist to decide between HVAC zoning and two different HVAC systems for a two-story home,
Consider HVAC zoning if:
- Budget is a concern
- The temperature difference between floors is relatively small
- The home’s layout isn’t complex and the entire home isn’t large
- Ductwork in HVAC systems is in good condition
Consider Dual Systems if:
- You prioritize maximum comfort
- The temperature difference between floors is significant
- The entire home’s layout is complex
- Existing ductwork is inadequate or needs replacement anyway
If you are building a new house, go with the zoning. But if you already have an HVAC system installed in your two-storied building and it is unable to cover both floors, it is best if you get another HVAC system and use two heating and cooling systems instead of one. If you live in a moderate climate, a heat pump system could be a very energy-efficient option for either a zoned or dual HVAC system.
Keep the maintenance and repair requirements of your HVAC system also in mind. A well-maintained cooling system is essential for summer comfort.
Dual Zone HVAC System vs Two Units
Most of the multi-zone system upsides and downsides are also applicable to two-zoned system.
Having two zones works similarly to two separate systems. So, is dual-zone HVAC worth it over the two separate units? It all comes down to the space and budget.
Setting up a dual-zone system is cheaper but with less control. If you have two separate HVAC systems, it can create a totally different atmosphere on two different floors or spaces. Since 2 zone HVAC system comes from 1 unit, the variation won’t be that much.
The Final Verdict: Making the Smartest Investment
Choosing between HVAC zoning and two systems comes down to what works best for your home and needs. Zoning is great if you’re on a budget, have smaller temperature differences, and your ductwork is in good shape. It’s also a good option for smaller or simpler homes.
On the other hand, if you want top comfort, have a bigger entire home, or deal with big temperature swings, dual systems might be the way to go. They cost more in the expense of more control. If you’re considering a dual system, it’s worth exploring high-efficiency options like heat pumps to offset the higher operating costs
Think about your entire house size, layout, and how much you’re willing to spend. Either way, the right HVAC system will keep your two-story home comfortable all year long.
Ready to finally solve your home’s temperature battles? Contact the GreenLeaf Air team today. We can evaluate your home’s layout, ductwork, and your family’s needs to provide a clear, personalized recommendation and quote.
