This section deals with the determination of heating equipment efficiencies, thermal distribution (air or hydronic) efficiencies, infiltration, and thermostat management. The energy consumption for most types of heating and cooling equipment is estimated using the DOE-2 building simulation program (version 2.1E), developed by the U.S. Department of Energy (Birdsall et al., 1990). A companion report (Warner 2005) describes the thermodynamic modeling of the home, and the relevant characterizations of the building’s thermal envelope (windows, insulation, etc.) The program performs a sophisticated series of calculations, modeling the energy consumption in the user’s house in a full annual simulation for a typical weather year (involving 8760 hourly calculations). Users can choose from approximately 293 weather locations around the United States. More details about the DOE-2 model and documentation of the current input file are provided here. Energy use for some heating and cooling equipment types are estimated independently of DOE-2 and are documented in this report. Interactions between space-conditioning equipment and the waste heat from occupants and appliances are also treated in the modeling process.
User inputs (or defaulted values, where user-entered values aren’t available) are gathered together and sent to the DOE 2.1E model to calculate the heating and cooling (and water heating if user specified that water heating was tied to a central boiler system) energy consumption. The DOE 2.1E model requires inputs on the location (longitude, latitude, altitude, etc.) and climate (a specified “weather city” corresponding to a TMY, TMY2 or CTZ weather tape) of the house; general information about the house (orientation, stories above ground level, ceiling height, house shape and dimensions, etc.); construction details about the house (roof/ceiling/wall/floor/foundation construction details; type, size, shading and location of windows, skylights and doors; external shading (garage location, size of surrounding trees); details on the heating and cooling equipment (equipment type, efficiency, duct location, thermostat type and settings); and information about occupants and other sources of internal gains.