Comparing real-world, as-applied system efficiencies and lifecycle costs is easier.
For many years, HVAC industry professionals have lamented the inadequacy of efficiency ratings to evaluate different system types equitably. Suffice it to say, the cornucopia of efficiency rating systems (including EER, IEER, SEER, AFUE, COP, and others) makes the task of comparing real-world, as-applied system efficiencies and lifecycle costs a lengthy, arduous task. That is, until recently.
Members of the Hydronics Industry Alliance-Commercial (HIA-C), a committee of the Radiant Professionals Alliance, Mokena, IL (radiantprofessionalsalliance.org), recognized the importance of creating a common denominator among all HVAC system types. This allows building owners, mechanical engineers, and design/build contractors to accurately compare real-world performance in a specific building. Ideally, this could be done in the early design phase, even before ground is broken. The idea emerged about five years ago, and the software has now come to fruition.
Available at no charge, the Building Efficiency System Tool (BEST, besthvac.org) is a commercial-building, total HVAC system comparison tool that addresses the challenge of accurately comparing different styles of HVAC systems.
With the very simplest of inputs, BEST compares the energy performance, first cost, life-cycle cost, and more for all major types of HVAC systems and is broadly applicable to most commercial buildings, anywhere on the continent. All BEST outputs are represented in operating dollar figures, making comparison easy.
BEST compares as many as four system types in a matter of minutes, instead of hours or days. The software was not created to replace programs like EnergyPlus (energyplus.net) required by some rating agencies, but BEST efficiently narrows the choices often run in EnergyPlus, significantly reducing design time. EnergyPlus is a free, open-source, and cross-platform that runs on the Windows, Mac OS X, and Linux operating systems. Its development is funded by the U.S. Department of Energy’s (DOE), Washington, Building Technologies Office (BTO, energy.gov/eere/buildings/building-technologies-office).
“While different types of HVAC equipment are subject to various rating systems, the bigger issue is that they’re all tested to different standards,” said Greg Cunniff, manager of application engineering at Taco Comfort Solutions, Cranston, RI (tacocomfort.com).
“The testing parameters, lab procedures, and resulting efficiency scores for some types of equipment are relatively comparable to their real-world performance,” added Cunniff. “For other systems, the discrepancy between tested and as-applied performance is surprisingly large. Owners, engineers, and contractors needed a tool that refines the choices and compares all technologies on common ground.”
“With BEST, professionals can rapidly analyze all the real-world HVAC options to determine the system that best meets budgetary and performance requirements,” said Rick Bostian, HIA-C chairman and business-development manager at WaterFurnace International, Ft. Wayne, IN (waterfurnace.com).
“In its most basic comparison function, the user only inputs the location for weather and utility data, building size, and number of stories to get a comparison of four options among the 30 predetermined systems,” Bostian continued. “If desired, the design team can change any of the program’s defaults to more closely match the building. Without BEST, comparing a lot of ‘what if’ scenarios can be expensive and time consuming.”
BEST uses the Building Energy Efficiency Ratio (BEER), which combines certified Air Conditioning, Heating, Refrigeration Institute (AHRI, ahrinet.org) data, including certified unit efficiency ratios, manufacturers’ published performance data, component performance curves, and the pipe or duct required in typical systems with “as applied” correction factors. BEST bridges the gap between laboratory test data and real world HVAC system performance, including installation and utility costs against calculated load and actual local weather.
“BEER rerates published efficiency data for actual operating conditions and any distribution energy that’s missing from AHRI data,” said Mark Handzel, vice president of product regulatory affairs at Xylem, Rye Brook, NY (xylem.com). “For example, pumping energy in a hydronic system is absent from AHRI numbers. And when VRF systems are AHRI tested in a lab, the demands on the compressor, based on length of refrigerant lines and load applied, are far less than what a typical field installation is likely to include.”
This type of rerate is applied in BEST according to American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta (ASHRAE, ashrae.org), guidelines. Certified manufacturers publish data to all systems by identifying, by system, where energy is used to deliver comfort. These rerates are standard defaults in BEST, where most other programs require users to make their own adjustments.
While a building’s heating, cooling, and ventilation energy consumption and operating cost is of great importance, the intent of BEST is not to predict annual energy consumption of a given system.
Rather, BEST seeks to provide the user with a comprehensive comparison of multiple, complete HVAC systems using an identical load profile, specific to building size, weather pattern, and installation and operating cost. BEST reports, in detail, the information needed for informed decisions regarding HVAC system selection at the early project design phase.
“BEST outputs cumulative lifecycle cost by year, system payback time, pump and fan HP, total system integrated energy efficiency ratio (IEER) for cooling, coefficient of performance (COP) for heating, and more,” explained Mark Chaffee, Taco vice president of governmental relations & sustainability, and founding member of the HIA-C. “The cost data is based on industry averages for first cost and maintenance costs collected from over 50 contractors around the U.S.” Five years in the making, BEST already has roughly 2,000 registrants.