RP-1199 -- Updating the ASHRAE/ACCA Residential Heating and Cooling Load Calculation PDF

ASHRAE Research Project RP-1199 developed two new residential heating and cooling loads calculation procedures:

• Residential Heat Balance (RHB), a detailed heat balance method that requires computer implementation; and
• Residential Load Factor (RLF), a simplified procedure suitable for hand or spreadsheet use.

RHB is based on first-principles heat balance models. A research-oriented FORTRAN implementation of RHB, designated ResHB, was developed using ASHRAE Loads Toolkit as a starting point. ResHB includes algorithms for calculating sensible cooling loads with temperature swing (temperature excursion above the cooling set point) and to handle master / slave control (room cooling controlled by a thermostat in another room). ResHB extends Toolkit capabilities to multiple rooms, zones, and systems, thus supporting load calculations for real buildings. Also added were infiltration, internal gain, and duct loss models appropriate for residential problems. Because RHB is a first-principles heat balance procedure, it can be directly validated and refined using empirical data.

ResHB was tested against the general-purpose building model ESP-r. Testing procedures and results are presented in the final report. Additional analytical, emprical, and inter-model validation of RHB is underway and will be reported in the literature when complete.

The RLF method was developed from RHB results. The form of RLF resembles prior methods. However, the sensible cooling load procedure was derived using linear regression to find relationships between design conditions, building characteristics, and peak cooling load predicted by RHB. This eliminated the need for semi-empirical adjustments, such as averaging, that have been used in the development of other methods. Results comparing RLF to RHB are presented. The RLF heating load calculation is also described; it uses the traditional UA deltaT formulation with some improvements to procedures for slab and basement ground losses and infiltration air leakage.

This project was supported in part by the Air Conditioning Contractors of America Educational Institute.

This download includes only the final report. A CD containing the final report, ResHB source code, and other development material produced during the work is also available for purchase.