Match VRF to your building’s loads, location and lifecycle costs
Variables create anxiety. We want to remove as many variables as possible from a situation. However, you
can embrace the variables in variable
refrigerant flow (VRF) systems
because they are a major contributor
to their efficiency. But you will need
to address some variables about your
building in order to determine if VRF
technology is a good retrofit option.
A VRF system’s variable flow of refrigerant via variable
frequency drive (VFD) motors allows the system to adjust
to a variety of loads. The refrigerant serves as both the
heating and cooling medium that can be delivered to multiple fan-coil units from a single outdoor condensing unit.
A VRF system with heat recovery allows indoor units to
cool or heat as necessary. For example, instead of rejecting heat from a server room to the outside, a VRF system
can move the heat to perimeter spaces that require it.
For retrofit applications, VRF can offer a solution for
inefficient fans and leaky ductwork. Buildings with inadequate cooling may be a particularly good fit. Older facilities and historical buildings, which often cannot easily
accommodate new HVAC equipment, may also be targets
for VRF solutions.
If you’re considering a major retrofit of an existing
HVAC system, take these three steps to do your due diligence for a possible VRF solution, says Anne Wagner, energy efficiency engineer at the Pacific Northwest National
1) Screen by building characteristics – Some older
buildings may provide better paybacks for VRF than new
ones, according to Variable Refrigerant Flow Systems,
a technology assessment prepared under GSA’s Green
Proving Ground program ( www.gsa.gov/greenproving-
ground). Wagner, who is a co-author of the publication,
points out that buildings with high energy usage, particularly those with VAV systems with electric reheat or other
electric resistance heat, may be good candidates. Facilities
with limited space to add ductwork for additional cooling
capacity may also be good candidates. The comparatively
small size of VRF refrigerant lines makes them easier to
install than ductwork even when buildings have adequate
The GSA report notes a number of factors to consider
when evaluating a cost-effective match with VRF technology. The zonal capability of VRF fan units are well-suited to
facilities with separated spaces, including schools, lodging,
multifamily, healthcare, some shopping centers, and office
buildings with numerous enclosed spaces and conference
rooms. Conversely, big box retail, warehouses, and other
facilities with large open spaces are not typically suitable.
Climate is also a factor, with extreme weather being a
plus. Colder regions may offer better opportunities for heat
recovery and may increase savings if converting from any
type of electric resistance heating. Conversely, buildings in
mild climates that often operate in an economizer mode will
benefit less. According to the report, a sweet spot for VRF in
terms of building size is 10,000–100,000 square feet.
2) Do an energy analysis – Have your building
surveyed to understand how, where, and when it uses
energy – and wastes it. Energy engineers recommend
incorporating a minimum of one year’s worth of detailed
consumption data in order to model the building through
the seasons. The analysis will provide a platform for determining proper size as well as estimating the efficiency and
cost of new systems.
By Chris Olson, Content Director