VRF Technology: Applications of Variable Refrigerant Flow in Multifamily Housing and Commercial Buildings

How do you meet multiple heating and cooling demands at one time? This is the question that variable refrigerant flow systems answer. This technology, originally invented by Daikin Industries, LTD in 1982, has made it possible for commercial and multifamily buildings to supply both heating and cooling to multiple zones simultaneously.

So how does a VRF system benefit multifamily housing and commercial buildings? In more than a few ways, to be concise. In this article, we’ll explore the technology, installation requirements, and benefits of a variable refrigerant flow system in multi-use buildings.

What Is Variable Refrigerant Flow?

In a conventional HVAC system, the mechanical components of the cooling and heating system are separate. For example, most single-family homes have both a furnace (heating) and an air conditioner (cooling). While the two may be stacked together in a single unit, they have separate mechanisms to provide the heating and cooling.

These separate units use air ducts to transport heated or cooled air throughout the home and then return that air through more ductwork before it is reconditioned. These forced air systems are widespread in homes and even some apartments.

Variable Refrigerant Flow systems, on the other hand, are built as single units with an interior evaporator and an exterior compressor. These two components, along with a condenser and an expansion valve, provide both heating and cooling through a single mechanism. Instead of forced air, VRFs act as heat pumps to condition the ambient air throughout the units.

How Do VRF Systems Work?

The main components of any HVAC system are the compressor, the condenser, the evaporator, and the expansion valve. This is true for VRF systems as well. Variable refrigerant flow systems use these components a bit differently, though.

In a typical air conditioning system, the refrigerant flows through the system at a constant pressure while the system regulates that pressure with temperature and compressor speed. As the refrigerant is pressurized, its temperature increases, and as pressure reduces, so does the temperature of the refrigerant. This closed loop is designed for a single load capacity, so the system is basically on or off.

But if your building is designed with multiple ambient zones, such as offices or apartments, a single conventional system can’t provide varying demands at the same time.

VRF systems solve this problem by adding a control box with multiple expansion valves and reversing valves, along with a variable speed motor for the compressor. The system can then send refrigerant through the condenser to provide cooling where demanded while simultaneously sending the same refrigerant directly to evaporators where heat is demanded.

And as refrigerant demand increases, the compressor increases speed to accommodate the demand. The pressure remains constant, keeping the system from freezing up or overheating.

With multiple evaporators running to a single compressor, you can design systems that provide multi-zone air conditioning to a single unit or coordinate multiple single-zone units for a larger multifamily building or multi-use commercial space. And the VRF system can be scaled almost infinitely.

What Are the Advantages of a Variable Refrigerant Flow System?

If you’re familiar with designing and planning commercial or multifamily buildings, you can see some considerable differences between conventional forced air systems and VRF systems right away. The delivery methods are different. The equipment requirements are different. And the installation processes have different demands.

And these differences make VRF systems worth considering over familiar forced air systems. While the initial equipment investment is often more than conventional stack systems, variable refrigerant flow systems could reduce energy costs by 30% or more.

  • VRFs require no ductwork, reducing engineering complexity and installation costs.
  • With no ductwork for heat loss, energy transfer is more efficient.
  • With less surge to both system pressure and electrical demand, the components in variable refrigerant flow systems experience less wear.
  • With less wear and tear to the system components, VRF systems require less maintenance over their lifetime.
  • When heating and cooling demands are relatively similar, variable refrigerant flow systems act as heat recovery systems, further reducing operating costs.

Why Choose Variable Refrigerant Flow Instead of Forced Air?

Forced air systems are more familiar to most HVAC technicians, but they have limitations, especially for larger buildings. A variable refrigerant flow system could be the right solution for your project, but it depends on a few key factors.

What Space Can You Dedicate to Equipment?

Forced air systems require an outdoor compressor and an indoor evaporator, furnace, and fan system. In many apartment buildings, units with forced air systems have a closet space inside the living area that houses the indoor equipment, while a deck or balcony provides space for the compressor. This equipment, no matter where it’s placed, will reduce the usable space for tenants.

Variable refrigerant flow systems utilize interior evaporators, usually installed on walls, connected to a smaller compressor outside of the unit. The HVAC closet is eliminated from the interior, and the compressor’s smaller footprint means more space on decks or patios.

Is Ductwork Possible?

Some retrofit projects make adequate ductwork difficult to install. And at times, the space required for ductwork simply isn’t available. VRF systems don’t require large air ducts for transporting conditioned air. Instead, the ambient air is conditioned directly by the evaporators.

What Types of Loads Will I Expect?

If your space requires different heating and cooling setpoints simultaneously, a conventional stack won’t provide the conditioning you need. However, if you expect a single setpoint for the HVAC system, stacks are a less expensive initial investment.

In larger applications, VRF systems also have the benefit of scaling well above their load ratings, as much as 130% of the compressor’s rate at times. That’s because the refrigerant demands vary from evaporator to evaporator. Where it’s needed, the control box will send refrigerant. As many as four additional evaporators could be connected to a single VRF system, depending on the building design and requirements.

How Much Am I Willing to Spend?

Instead of asking how much, it’s worth asking where you want to spend your money. Upfront costs are important for building projects. Variable refrigerant flow systems use much less energy than conventional HVAC systems, but they come with a higher price tag. If you want to save on initial costs, VRFs will be a hard sell. But you’re likely to lose those cost savings quickly as your energy bills come in.

For a long-term investment that pays for itself, VRFs are hard to beat. We mentioned the energy savings above, possibly cutting your heating and cooling costs by a third. When designing your multifamily building or commercial space, consider your long game as much as the immediate cost to make sure you’re choosing a system that works best for your needs.

Am I Seeking Green Certification?

Many new buildings want to be certified as green designs. Environmental responsibility isn’t just practical; it’s also attractive for renters. Conventional stack systems have improved greatly over the last 50 years, but they still can’t compete with the efficiency of VRFs. Modern green buildings need HVAC systems that match their commitment to environmental responsibility. Variable refrigerant flow does just that.

Conventional or VRF: We Know It All

Whether your cost analysis points to conventional stacks or VRFs as the best solution, Innovative Engineering Solutions is ready to design and install the perfect system for your next commercial or multifamily project. With decades of experience between our team members and incredible facilities to demonstrate our expertise, you can be confident that your investment was the right choice.

Contact us today to set up an appointment to explore your mechanical design needs. We know it all: HVAC, plumbing, electrical, and automation. Be confident that your tenants will experience the pinnacle of comfort in your property.