The recent ASHRAE project, “Updating the ASHRAE/ ACCA Residential Heating and Cooling Load Calculation Procedures and Data” (1199-RP), developed two new residential load calculation procedures: residential heat balance (RHB), a detailed heat balance method that requires computer implementation, and residential load factor (RLF), a simplified procedure that is hand tractable and suitable for spreadsheet implementation. This paper describes RHB and its development. For calculation of sensible cooling load, RHB applies the general approach of the ASHRAE heat balance (HB) method, based on room-by-room 24-hour design-day simulation. The 24-hour procedure eliminates issues of gain diversity that are troublesome in prior single-condition methods. RHB includes algorithms for calculating sensible cooling loads with temperature swing (temperature excursion above the cooling setpoint) and to handle master/slave control (room cooling controlled by a thermostat in another room). RHB is implemented in the ResHB FORTRAN 95 application, developed by modification and extension of the ASHRAE Loads Toolkit. The paper documents RHB/ResHB models and modeling assumptions. Because RHB is a first-principles heat balance procedure, it can be directly validated and refined using empirical data.

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