Rating System

LEED BD+C: New Construction

Rating System Version

v2 - LEED 2.1

Inquiry

DRAFT CREDIT RULING REQUEST FOR MSP PROJECT - SAFEWAY STORE ENERGY MODEL IMPACTS Our question is in reference to a mixed-use (residential/commercial) building that will be occupied in part by a large grocery store. The tenant improvements for the grocery store, including the casework and mechanical systems for refrigeration, are part of the scope of work covered by our LEED project, and will all conform to any LEED credits and prerequisites we attain. The store will contain extensive refrigeration casework which will generate waste heat, for which we will have to provide cooling in summer months, and which we will capture to use for commercial space heating in winter months. The casework also provides "waste cool", throwing off cool air into the store year round. This waste cool will require additional heating for the space in winter months, but provide some free cooling in summer months. Our question is about how to appropriately capture these thermal impacts and benefits in our energy model. Our energy modeler has told us that conventional modeling protocol allows him to include the recaptured waste heat from the process loads in the design case model, and exclude them from the base case model, so we can capture the heating benefits of captured waste heat, just as we are penalized by the additional cooling load that heat imposes in the summer. However, he explained that cooling benefits provided by the refrigeration equipment is included in both the base case model and the design case model, so no \'free cooling\' benefit shows up in the model. He said the cooling provided by the casework would improve our model by enough margin to move us up at least on Energy Credit 1 threshold. The grocery tenant is on a 30-year lease: approximately the life-span of the mechanical equipment. Unlike simple energy-efficient appliances, which are excluded from energy models for LEED purposes, these systems are fully integrated with the base building HVAC design. The mechanical system designer puts it this way: "The environmental control of the grocery store, like all retail food stores, is integrally tied to refrigerated case work. The refrigerated cases provide a cooling load on the space continuously, 365 days a year. This benefits the HVAC cooling load in the summer and burdens the heating load in the winter. Therefore, the HVAC system is customized to this load, and designed to mitigate energy consumption. "The cooling capacity of the main air handler is substantially reduced, taking credit for the refrigerated case work. The heating capacity is substantially increased to offset the refrigerated case work. To reduce the high energy use for heating, heat recovered from refrigeration compressors is the primary source of heat for the store. "The store also has a significant latent load from products, requiring dehumidification. This is accomplished by sub-cooling and reheating the air. Again, heat recovered from the refrigeration compressors is the primary source of heat. "In short, the HVAC system for the store is designed to address the case work loads, and uses the rejected heat. Without the case work, the HVAC system design would have to be changed." We propose that we be allowed to capture the energy efficiency benefits of the cooling provided by the grocery store refrigeration equipment within our energy model.