How to Design an Efficient Zoned HVAC System
- by Emily Newton
- 2022-10-12 00:00:00
Many residents complain of hot and cold areas in their homes. Alternatively, they might often mention that the rooms they hardly spend time in feel nice while the most frequently occupied areas are uncomfortable. These are some situations where a zoned HVAC system is most appropriate.
It can keep the temperature consistent in multiple areas of the home, courtesy of dampers that open or close depending on how much heat or coolness a particular room needs at a given time. Here are some helpful things engineers should consider when designing an HVAC zoning system that works effectively and efficiently.
Proceed Differently When the Project Is a Retrofit Versus New Build
The design process varies depending on whether the client wants the zoned system in a new building or one that’s getting an addition or remodeling. One design tip is ensuring that any new section or room has a thermostat. That’s because the updated parts of a home will typically have better insulation than older ones.
A zoned HVAC system has a thermostat in each area, dampers to control the airflow and a control panel that allows a person to manipulate everything in one place. Those components remain part of the setup regardless of whether the project is a retrofit or a new build. However, the main difference in new construction is that the installation professional has more options. When handling a retrofit, people are somewhat limited by what’s already there.
An existing system usually has a main supply duct and at least one branch supply duct per room. Installers must put dampers on all the branches, then connect them to that zone’s thermostat. When the branch supply ducts are behind drywall or otherwise hard to access, an option is to insert the dampers through registers or install them.
However, when the zoned system is on new construction or a project requiring new ductwork, installers can have one main supply duct per zone. They can put the dampers on those instead of the branch supply ducts. The main benefit of that approach is that the system uses fewer dampers.
One thing to be mindful of if adding zoning to an older home is that the overall project costs can rise if the ductwork is difficult to access. However, in such cases, the people overseeing the system planning should remind clients of the benefits. Those typically include better occupant comfort and significant energy savings.
Become Familiar With the Structure’s Layout and Usage Patterns
Today’s homeowners have many options to consider when deciding how to make their abode as pleasant and livable as possible. For example, many residential and commercial buildings have polyvinyl chloride panels on their ceilings. They promote heat and UV insulation, which can lower energy costs. Designing a zoned HVAC system that works well requires understanding the building’s layout, features, architecture and how occupants typically use the space.
Here are things to think about for a residential space. Each floor of the home should have a separate zone. However, other considerations will shape more complex design decisions. For example, does the room have glazed windows or overexposed floors? Those things will influence what’s necessary to keep the residence comfortable. Evaluate how much sun exposure particular rooms get per 24 hours, too.
How the home’s usage changes during different times also matters. Many households probably spend the most time in their bedrooms at night. However, that’s not necessarily the case if people in the residence work odd hours or must be on-call during some nights of the month.
Planners must pay close attention to the ratio of cool to warm airflow in each room. Keeping it well-balanced will prevent the hot and cold spots that efficient zoning avoids. Achieving the right proportion is especially important if using the same ducts for cooling and heating.
It’s also ideal if each zone contains areas open to one another. They’ll promote good air circulation and get the best temperature balance at the optimal efficiency.
Build the Zoned HVAC System After Improving the Building Envelope
People have numerous drivers encouraging them to make upgrades to their homes. For example, some want to remove toxins and improve indoor air quality with smart HVAC systems. However, as previously mentioned, one of the primary perks of a zoned HVAC system is that it improves people’s comfort while in the home.
It’s a best practice to only proceed with zoning once a client has an energy audit performed by a qualified professional. A home might be uncomfortable for the occupants because it’s very leaky and has many drafts. An auditor’s recommendations could bring notable benefits even before the zoning efforts begin.
For example, exterior insulation on the building envelope improves the walls’ thermal resistance. The addition of preinsulated wall panels can also help. Tiny openings around windows, doors, pipes and ductwork can let air enter or escape a building. Sealing them with caulk is an effective way to make a continuous pressure and thermal boundary.
Attention to a home’s attic and crawlspace is also advisable, especially since people often overlook those areas. Sealing and encapsulating the crawlspace and sealing wiring penetrations in the attic are good starting points.
These tips don’t suggest it’s no longer necessary to install a zoned HVAC system after making building envelope improvements. However, it’s best to take these measures first. Otherwise, the impacts of the HVAC installation may not be as noticeable because the envelope remains unoptimized.
Ensure the Controls Are User-Friendly and Efficient
Clients are much more likely to be happy with their zoned HVAC system for the long term if they can quickly and easily adjust the settings. Most of today’s options work over Wi-Fi and allow people to control them with smartphone apps.
If the climate controls include smart thermostats, people may choose to use geofencing technology so certain things happen depending on if they’re at home or away. It works similarly to a zone-based HVAC system. A smart home device with geofencing activated usually detects the location of a person’s phone before going into different operating modes. If an occupant’s smartphone is out of the house, that probably means they are, too.
The possibilities for making such setups work well and match how people live are virtually endless. Consider a case where someone has a smart lock on their front door and a smart thermostat in the home that connects to a zoned system. In that case, they might specify that the home temperature drops whenever they leave the house to go to work. That could help save energy.
In another case, researchers compared a multizone, Wi-Fi-controlled HVAC system with a single-zone setup to learn about potential energy savings. The specially designed technology accomplished a few things. It maintained the desired temperature in each zone and controlled the opening area of the vent registers and the velocity of the fan in the indoor unit. Together, these functions made the setup more efficient.
Results from the study indicated the multizone system was 75%-94% more efficient than the single zone when researchers selected only one. Moreover, the multizone setup had a 44% efficiency boost when the whole house was air-conditioned. People designing HVAC systems for clients will get the best results when they take the time to determine how residents plan to use their systems and what features they want most.
Remain Thoughtful at Every Phase of the Zoned HVAC System Design
These are some of the main things people should remember when designing an HVAC system with multiple zones. However, they should also remain flexible and realize that some of the best-laid original plans may not work as well as expected. When someone gets deeper into the design process, it often becomes apparent that they failed to consider everything at the start. However, understanding how certain decisions could affect the entire process is an excellent way to avoid pitfalls.
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