Hydronic systems outperform VRF, study finds
In a study commissioned by Xylem Inc. that evaluated HVAC systems in a number of South Carolina school buildings, hydronic systems outperformed all other systems, including VRF, in terms of lower energy use, cost and life expectancy, by as much as 24%.
“With HVAC systems dictating a substantial amount of the overall energy use of commercial buildings, the results shed light on the importance of evaluating varying system-to-system costs before installation,” said Kyle DelPiano, Business Development Director, CBS Market, Xylem. “More than ever, energy-efficient practices are driving the construction industry toward more sustainable solutions, and this study proves long-term cost savings that can’t be overlooked when making the choice between hydronic and VRF systems.”
To compare and contrast HVAC systems according to their 30-year life-cycle cost analysis (LCCA), the Xylem study analyzed seven elementary and middle schools located in South Carolina Climate Zone 3A, a humid, warm climate. The cost analysis included upfront installed cost, replacement cost allocations and ongoing energy and maintenance cost of the following system types:
- Variable refrigerant flow heat pumps (VRF)
- Water source heat pumps (WSHP)
- Ground source heat pumps (GSHP)
- Direct expansion rooftop units (DX RTU)
- Water cooled chillers (WCC)
- Air-Cooled Chillers (ACC)
The findings of the study revealed that the schools with WSHP, GSHP and WCC systems displayed energy use levels that were 30%, 41% and 25% better than the national median for elementary and middle schools, respectively. The replacement cost allocation also acknowledged that the tested hydronic systems operate effectively for approximately 25 years, as opposed to the 15-year replacement estimation for VRF systems.
The tested VRF systems required replacement a decade earlier because of their tendency to work harder during heating cycles, bringing proof of long-term cost savings to the forefront of the conversation surrounding sustainability and hydronic HVAC system efficiency.
Replacement allocations had an impact on the life-cycle cost analysis (see yellow bars) and drastically reduced the cost effectiveness of equipment with 15-year life expectancies.
Considerable benefits of the hydronic HVAC systems included lower energy usage intensity and cost, wider range of maintenance flexibility and longer life expectancy.