A recast of a presentation done for the Fairfax Chapter of Association of Energy Engineers in November of 2013. Presentation focuses on the the Advanced Energy Design Guides published by ASHRAE with association of AIA, USGBC, and IES with funding and technical support from DOE, NREL, and PNNL. In addition, the DOE Advanced Retrofit Guides are also discussed. Both sets of guides are available for download from this resource database.
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In 2011, the U.S. Department of Energy’s Building Technology Office (DOE’s BTO), with help from the Better Buildings Alliance (BBA) members, developed a specification (RTU Challenge) for high performance rooftop air-conditioning units with capacity ranges between 10 and 20 tons (DOE 2013). In April 2013, Carrier’s 10-ton WeatherExpert unit model was recognized by DOE to have met the RTU Challenge specifications. Carrier also committed to have its entire line of WeatherExpert models for commercial buildings compliant with integrated energy efficiency ratio (IEER) meeting the RTU Challenge requirement. This report documents the development of part-load performance curves and their use with the EnergyPlus simulation tool to estimate the potential savings from the use of WeatherExpert units compared to other standard options.
A detailed EnergyPlus model was developed for a prototypical big-box retail store. The model used the performance curves from the new model along with detailed energy management control code to estimate the energy consumption of the prototypical big-box retail store in three locations. The energy consumption by the big-box store was then compared to a store that used three different reference units. The first reference unit (Reference 1) represents existing rooftop units (RTUs) in the field, so it can be considered the baseline to estimate potential energy savings from other RTU replacement options. The second reference unit (Reference 2) represents RTUs in the market that just meet the current (2015) Federal regulations for commercial equipment standards, so it can be used as the baseline to estimate the potential for energy savings from WeatherExpert units in comparison with new RTUs that meet the minimum efficiency requirements. The third reference unit (Reference 3) represents units that meet ASHRAE 90.1-2010 requirements. For RTUs with cooling capacity greater than 11,000 Btu/h, ASHRAE 90.1-2010 (ASHRAE 2010) requires two-speed fan control or variable-speed fan control.
The following conclusion can be drawn about the comparison of energy cost for WeatherExpert unit compared to the three reference units:
• Using Reference 1 as the baseline, WeatherExpert units result in about 45% lower heating, ventilation and air conditioning (HVAC) energy cost in Houston, 55% lower cost in Los Angeles, and 35% lower cost in Chicago. The percentage savings of electricity cost is more than 50% for all three locations.
• Using Reference 2 as the baseline, WeatherExpert units result in about 39% lower HVAC energy cost in Houston, 52% lower cost in Los Angeles, and 32% lower cost in Chicago. The percentage savings of electricity cost is 44%, 55%, and 57%, respectively for the three locations.
• Using Reference 3 as the baseline, WeatherExpert units result in about 25% lower HVAC energy cost in Houston, 35% lower cost in Los Angeles, and 18% lower cost in Chicago. The percentage savings of electricity cost is 29%, 38%, and 37%, respectively.
Based on the simulation results, the WeatherExpert RTU Challenge unit, if widely adopted, could lead to significant energy, cost and emission reductions. Because the cost of these units was not available and because the costs would be specific to a given installation, no attempt was made to estimate the potential payback periods associated with any of the three reference scenarios. However, if the incremental cost relative to any of the three reference cases is known, one can easily estimate a simple payback period.
On December 6, 2016, the U.S. Department of Energy announced the launch of a new partnership to jump-start zero energy schools across the country. The Zero Energy Schools Accelerator enables states and school districts alike to design, construct, and operate these cutting-edge, energy-saving schools. This press release highlights the importance of the Accelerator by featuring a completed zero energy school, Discovery Elementary in Arlington, Virginia.
This case study describes a successful zero energy school project in Utah.
This case study details the successful achievement of Passive House performance and zero energy at the Friends School of Portland.
The Energy Lab at Hawai’i Preparatory Academy is the third building worldwide and the first K–12 school facility to achieve “Living” certification through the Living Building Challenge (LBC). This case study details how the project succeeded in these goals.
On the night of May 4, 2007 an EF5 tornado 1.7 miles wide ravaged Greensburg, Kansas, destroying 95% of the city's homes and businesses. In the wake of the disaster, it became apparent that changes would need to occur to sustain the town for future generations. The Greensburg School District selected BNIM Architects to provide comprehensive design services for new school facilities.
In direct alignment with the town's Sustainable Comprehensive Master Plan, the USD decided to rebuild to LEED Platinum. This decision led the way for the city, which later mandated that all public buildings attain a Platinum rating. This K–12 facility combines the resources of three rural community school districts into a single facility, thereby right-sizing at a regional scale.
Case study on how Fontana Unified School District in southern California used grant money to install 201 high-efficiency Carrier rooftop units (RTUs) in 30 buildings across four schools, resulting in $214,000 saved per year.
Case study on how Arby's Restaurant Group's innovative approach to rooftop unit (RTU) management garnered them $287,000 and 2.9 million kWh in annual savings.
This case study details the successful achievement of zero energy and Living Building Challenge certification.