Getting Out of Hot Water: Reducing Gas Consumption in Existing Large Commercial Buildings

Project Result

The project demonstrated 70% fossil gas savings and substantial electricity savings in two large office buildings, yielding total utility cost savings of approximately $110,000 (or $0.5/ft²) per year. The project also conducted detailed studies on distribution losses and boiler efficiency in several buildings; measured performance of key components in laboratory tests; gathered and analyzed data from hundreds of buildings to evaluate actual performance of these systems; and provided a public dataset to inform future retrofits, research, and code development. The research also highlighted characteristics that make a building a good candidate for retrofit so these results can be scaled. Market transformation activities included 10 journal and conference publications, policy recommendations and a design guide.
• The primary demonstrations reduced annual fossil gas consumption by 69% and 71% annually in two large office buildings, as well as substantial HVAC electricity savings. A third demonstration site, a recently constructed building in which the team made ultra low-cost, software-only controls changes in the non-lab portions of the building, yielded fossil gas savings of 22%.
• Substantial energy, cost, and emissions savings potential may be achieved in existing buildings by correcting variable air volume minimum airflows and bringing controls up to ASHRAE Guideline 36.
• The team identified that buildings with a heating hot water (HHW) by a single, older, non-condensing gas boiler likely have very poor operational efficiency—far below nominal efficiency—and should be prioritized for retrofit.
• The team acquired and analyzed data from HHW systems in 259 buildings nationwide, highlighting that many of the assumptions regarding how these systems operate do not align with real world performance. These systems operated far more frequently and less efficiently than expected, indicating substantial savings opportunities. The team released an open-access dataset of over 100 million measurements from 216 buildings nationwide.
• The team measured HHW distribution losses (i.e., standby losses) of 1.2 W/m² in 7 buildings, and validated those measurements with newly installed, high-quality instrumentation at both building and branch level in one building. The team also validated the intentional reheat method using that instrumentation, and repeated this analysis in a third building.
• The team developed a screening method to identify candidates with high savings potential based on monthly gas consumption and minimal building information.
• The team performed full-scale laboratory testing of HHW system components, including developing and testing a custom coil designed for low water temperature operation suitable for all-electric new construction and existing building electrification retrofits.
• The team published findings in a policy recommendations report, design guide, 10 journal and conference articles, as well as numerous presentations.