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Cold climate VRF systems

Application of air source variable refrigerant flow 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.

In colder climates, this often necessitates the addition of a supplementary heater within a partially-enclosed mechanical room housing the outdoor units. Because of their lower capital cost as compared to water or ground source alternatives, the majority of VRF systems being implemented in cold climates today are air source. However, significant questions remain regarding how to design and operate air source systems at low outside air temperatures.

Whitepaper and VRF analysis tool

Our white paper outlines the optimal control strategies for designing and operating air source VRF systems in cold climates.

In addition, a tool was developed (for free download) that allows designers to better understand the optimal design parameters of air source VRF systems.

How to download the tool:

  1. Go to
  2. Click “Sign in”
  3. If you haven’t created an account, click “Sign up”
    • Enter your information and click “Register”
    • You will receive an email (may take several days) when your registration has been processed
  4. Log in using your username and password
  5. Click on “Library”
  6. Select “08 VRV/LC Sales Partners”
  7. Select “Sales Tools & Applications Resources”
  8. Select “Sales and Applications Tools”
  9. Select “Cold Climate VRF Analysis Tool”
  10. Download .zip file

For additional assistance, contact sends e-mail).

VRF Tool

Key observations

This project was possible with significant funding from Daikin North America, LLC. Masters Building Solutions also provided technical input. The project would not have been possible without these two organizations’ assistance. Former Slipstream staffer Alisa Petersen also contributed to this project.