The North American HVAC industry is evolving with new trends and regulations emerging every day, and it’s not just HVAC technicians that need to stay ahead of these trends. HVAC is a critical allied trade for CE pros, as CEDIA’s most recent Professional Smart Home Market Analysis shows that most integrators frequently or always include HVAC control in their whole-home automation projects. Market trends indicate that number will grow.

For example, two-thirds of integrators worked on energy management projects in 2023, and nearly 40% worked on renewable energy / battery storage / EV charging projects. There is clearly growing interest in leveraging technology to create more sustainable homes, and HVAC is commonly among the most energy-hungry building subsystems.

If you’re helping a client build a greener home or office, their HVAC system is a core component of that. So, let’s examine common HVAC technologies and emerging trends through the lens of how they interact with home automation systems, and what you need to know to partner with your HVAC allies and meet your clients’ needs.

Types of HVAC Units

Most residential applications use either conventional fan coil units (cFCUs) or inverter (VRF / mini-split) units. The type of unit directly impacts efficiency, refrigerant charges, piping length, and control requirements.

Conventional Fan Coil Units (FCUs)

FCUs are the oldest and simplest HVAC unit design. They work by drawing air over a coil to heat or cool it, then pushing that air out into the space. Most conventional FCUs have only two states, “on” or “off.” There are two-stage FCU systems with “high,” “low,” and “off” states, which allows them to operate somewhat more efficiently.

Inverter (VRF / Mini-Split) Units

VRFs adjust the speed of the HVAC’s compressor motor, allowing them to operate at variable speeds rather than just “on” or “off”.  These units typically use Inverter heat pump technology to cool or heat air. Inverter units adjust output to demand, reducing wear on the system and making them significantly more efficient than even two-stage cFCUs.

Inverter HVAC technology dominates the global market, with over two-thirds of global unit sales as of 2022. In Asia and the EU, Inverter units are the norm, and adoption in the United States has been trending upwards thanks to government incentives for more efficient technologies, retrofits, and new builds.

As inverter (VRF / mini-split) units have gained popularity, however integrators have discovered that these sophisticated systems require more know-how to control than a conventional FCU.

What Makes Inverters So Complex to Control?

Conventional FCUs require only a handful of simple commands: “on”, “off”, change modes. As a result, they can be controlled directly by a third-party smart thermostat or other control device via 24V dry contacts without any loss of their limited features. 

Inverter HVACs are much more sophisticated. They do not have 24V dry contacts, instead relying on proprietary command protocols to manage variable speed operation and system diagnostics.

You need a dedicated control device to translate between an inverter unit and any IoT control solution, including any home automation platform. Without an add-on device to facilitate two-way communication, an inverter unit under IoT control downgrades to single-speed operation just like a conventional FCU.

Here’s one more important consideration: Conventional FCUs generally require a lot more electricity than Inverter HVAC units, but FCU-based systems require less refrigerant. 

In larger spaces, including both commercial buildings and elite homes, it can be challenging to meet ASHRAE 15 requirements with an HVAC system based on Inverter technology.

HVAC Legislation Has Been Trending Towards Greater Efficiency

What is ASHRAE 15 you might ask? First, ASHRAE refers to the American Society of Heating, Refrigerating and Air-Conditioning Engineers, and it serves as the main professional association that helps develops regulations for the North American HVAC market. ASHRAE 15 is the most recent set of guidelines aimed at implementing a standard for HVACs.

Over the years, the market has been slowly transitioning to more efficient technologies, however, the frequency and size of these developments have been ramping up as of late. For instance, on January 1, 2025, new rules go into effect that will phase out many common refrigerants in favor of greener A2L refrigerants.

A2L refrigerants contribute to global warming far less than traditional refrigerants like HFCs, but they’re also slightly flammable. The ASHRAE 15 safety standard therefore places limits on how much A2L refrigerant can be used per cubic foot of space.

The HVAC industry is under twofold pressure to become more efficient: to reduce Global Warming Potential (GWP) and to avoid unsafe concentrations of flammable refrigerant.

These transitioning refrigerant standards will ripple out to systems integrators, creating new business opportunities. ASHRAE 15 and the environmental concerns driving it will impact what kinds of HVAC units and technologies are connected to home automation, building control and energy management systems, and the control complexity required.

Zoning for Optimal Efficiency

Independent zone control is the key to both getting the most out of individual inverter HVAC units, and meeting ASHRAE 15 requirements for inverter-based systems in larger spaces.

With properly implemented smart control, an inverter-based system can control a home’s temperature with far better electrical efficiency than an FCU-based system.

A zoned system can be even more efficient, reducing refrigerant demands to well within ASHRAE 15 parameters.

A single inverter unit can control the temperature in several different zones of a proper HVAC system. (Courtesy of Airzone)

Zoned HVAC systems have different setpoints for different spaces throughout a building. With integrated occupancy sensors and smart controls, you can create automated setpoints that change based on occupancy, time of day, or control system mode.

For instance, you can program a system to start warming up the bathroom right before the client’s alarm is set to go off, while waiting to heat up the home office until after morning coffee.

The client can keep the gym cool and the living room cozy, or automatically change the temperature setpoint when the home is unoccupied. This system design has benefits beyond efficiency – it creates a more comfortable, luxurious, and responsive environment.

If your client is serious about sustainability, HVAC zoning and setpoint automation should be part of the needs discovery process. A single inverter unit can control the temperature in several different zones, and a single building may have several units.

As with single-unit control, zoned Inverter systems require sophisticated two-way communication between the unit(s) and the IoT control platform.

Any zoned system will require you to work closely with the project’s HVAC provider: You will need to know the number and location of zones; the make, model, and number of HVAC units; and the sensors and control equipment (such as thermostats) included in the HVAC system design in order to create an integration plan.

Creating Holistic Sustainability

There’s a spectrum of sustainability when it comes to HVAC technology. Inverters are greener than conventional FCUs. A zoned inverter system is more efficient than an un-zoned HVAC system.

An HVAC system that has been fully integrated with other building automation systems, including lighting, shading, automated scheduling, and occupancy sensors, is most sustainable of all.

These technologies have compounding effects. For example, in the winter, the system can dim the lights and lower the HVAC setpoint while raising the shades to let in the midday sun. The house will feel warm and bright with minimal energy expenditure, and residents will enjoy the biophilic benefits of natural light.

This whole-home orchestration results in a more efficient system that also feels luxurious and welcoming.

As you work to program these automations, recognize that both you and the HVAC services provider may be in unfamiliar territory. The industry is in flux, adjusting to new rule changes and market demands.

Communicate early and often, however, and you can deliver next-level sophistication, sustainability, and comfort.

Author Victoria Garcia Massimo is Director of North American Operations at Airzone.

• Page 1