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Variable refrigerant flow (VRF): HVAC electrification at a commercial scale

To optimize building performance, especially in commercial buildings, we often look at one of the biggest sources of energy use: the HVAC system. With the rising popularity of heat pumps and other forms of beneficial electrification in residential buildings, can we adopt an equivalent approach for commercial buildings? One solution is known as variable refrigerant flow (VRF)—an all-electric alternative to traditional HVAC systems that can make a building more efficient, reduce its carbon emissions, and prepare it for the clean energy future.

How does VRF work?

Typically variable refrigerant flow systems use electric air or water source heat pumps to provide space heating and/or cooling to a building. By moving heat throughout a building via refrigerant, rather than water or air, VRF uses energy more efficiently.

VRF systems can also condition multiple zones in a building (hence the "variable"), each of which may have different heating and cooling needs. Using sophisticated control technologies, VRF systems have the ability to modulate the amount of refrigerant sent to each zone independently and in tune with the varying heating or cooling demands, thereby reducing energy waste.

Benefits of VRF

  • In our estimation, VRF systems are three to four times more energy efficient than gas heating. As we move toward a fully renewable grid, electrified buildings will be better prepared for the clean energy future.
  • As opposed to traditional HVAC systems, VRF has several non-energy impacts that contribute to occupant comfort, including reduced noise and improved indoor air quality.
  • While air source VRF systems perform best in moderate climates, much of our research has focused on VRF as a solution for cold climates.

How It Looks:

Variable refrigerant flow systems can deliver cooling to some zones and heating to others.

Related Reads

An office building in a winter climate
Slipstream is looking for buildings to study variable refrigerant flow (VRF) systems in Minnesota. Read more
Application of air source variable refrigerant flow (VRF) in cold climates Variable refrigerant flow (VRF) systems use variable speed, split heat pumps to provide space heating and cooling to a building's conditioned areas. Air source VRF systems perform best in moderate climates, as they typically lose capacity and efficiency at low ambient temperatures—or moderately low wet bulb temperatures where defrost is required—and may be supplemented by an additional heat source. Read more
Variable Refrigerant Flow (VRF) systems have developed into a promising emerging technology. While popular in some places in the world, these systems are quite new to the upper Midwest. The systems are an innovative version of a simple split system air conditioner that utilizes variable speed compressors, multiple zone refrigerant distribution, heat recovery, and low energy fan coils to cool and heat commercial buildings more efficiently than standard split systems and heat pumps. Read more
This white paper outlines the optimal control strategies for designing and operating air source VRF systems in cold climates. Report number: 275-1 Read more