Don’t Drink the VRF KoolAid

If you search the web or talk to suppliers, some pretty impressive (and sometimes optimistic) energy savings figures are being quoted for VRF systems.  our recommendation is to conduct your own energy study and pay close attention to the climate. Our advice here is to have an energy analysis completed for your particular project to get a better understanding of what savings you are likely to realise from a VRF system compared with a second choice system suitable for your site.

Our experience, coupled with computer aided building thermal analysis is that ‘modest’ energy savings can be made, depending on geographical location, the use of double glazing as well as many other factors. A few pertinent points are:

In cooling operation, VRF systems offer broadly similar efficiencies to any other modern refrigeration based system.

However, central plant systems such as VAV (Variable Air Volume) offer a natural ability to provide ‘free cooling’ by supplying cool outside air whenever it is cooler than the building exhaust air temperature, and a cooling load exists in the building.  This is not the case with VRF systems that are designed only to use ventilation air – no free-cooling economizer at all!  Most climates in the US permit hundreds of hours of compressor-free cooling.  In North America’s predominantly temperate climate (particularly in the northern regions) this can provide significant energy savings. VRF systems do not provide this  free cooling capability. Instead, they recirculate room air, with a separate outside air system providing the minimum ventilation requirements.

 

Some designers are now incorporating over-sized outdoor air systems for use in conjunction with VRF systems. These are designed to deliver higher quantities of outside air under favourable conditions, effectively providing more free cooling, and reducing to compliance airflow rates in very warm or very cool weather.

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