TASK 2.5.4 DEVELOPMENT OF AN ENERGY SAVINGS CALCULATOR

California s major energy utilities and the California Energy Commission (CEC) are seeking to allocate capital that yields the greatest return on investment for energy infrastructure that meets any part of the need for reliable supplies of energy. The utilities are keenly interested in knowing the amount of electrical energy savings that would occur if cool roof color materials are adopted in the building market. To meet this need the Oak Ridge National Laboratory and the Lawrence Berkeley National Laboratory (LBNL) have been collaborating on a Public Interest Energy Research (PIER) project to develop an industry-consensus energy-savings calculator. The task was coordinated with an ongoing effort supported by the DOE to develop one calculator to achieve both the DOE and the EPA objectives for deployment of cool roof products. Recent emphasis on domestic building energy use has made the work a top priority by the Department of Energy s (DOE) Building Technologies Program. The Roof Savings Calculator (RSC) tool is designed to help building owners, manufacturers, distributors, contractors and practitioners easily run complex simulations. The latest web technologies and usability design were employed to provide an easy input interface to an annual simulation of hour-by-hour, whole-building performance using the world-classmore » simulation tools DOE-2.1E and AtticSim. Building defaults were assigned based on the best available statistical evidence and can provide energy and cost savings after the user selects nothing more than the building location. A key goal for the tool is to promote the energy benefits of cool color tile, metal and asphalt shingle roof products and other energy saving systems. The RSC tool focuses on applications for the roof and attic; however, the code conducts a whole building simulation that puts the energy and heat flows of the roof and attic into the perspective of the whole house. An annual simulation runs in about 30 sec. In addition to cool reflective roofs, the RSC tool will simulate high- medium- and low-slope roofs, and has a custom selection for the user whose house has a unique inclination. There is an option for above sheathing ventilation, which is prevalent in tile and stone-coated metal roof assemblies. The tool also accommodates the effects of radiant barriers and low-emittance surfaces in the inclined air space above the sheathing. The practitioner can select to have air-conditioning ducts either in the conditioned space or in the attic. If in the attic, the user can select one of three air leakage options. Option 1 is an inspected duct having 4% leakage and code level of duct insulation; option 2 is a poorly insulated duct having 14% air leakage; and option 3 is a custom leakage rate specified by the user. The practitioner can setup multiple layers of ceiling insulation. AtticSim is benchmarked against the field data acquired for Ft. Irwin located near Barstow, CA, first as a standalone simulation program and then again integrated within the DOE-2.1E program. The standalone benchmark was very useful to determining how well AtticSim replicates the building physics of an attic. The coupled benchmark was useful to verify that the DOE-2.1E/AtticSim code is modeling correctly the dynamic relationship between the attic and the occupied space below, as well as the interactions between the attic and the HVAC system, in particular when the ducts are located in the attic.« less