“…Firstly, the Handbook equation uses a constant load throughout the course of operation, with a magnitude equal to the average value, plus a peak "block load" for which no guidance is given on how to determine magnitude or duration; this peak block load is also coupled with the part-load factor for the design month to arrive at the value for the monthly thermal pulse. The design tool, on the other hand, uses a monthly time step, with loads input as monthly totals plus a monthly peak for both heating and cooling; Cullin (2008) describes how the peaks are selected in terms of magnitude and duration, while Cullin and Spitler (2011) show that this method of load representation performs very well, predicting design depths within ±7% of what would be predicted using an hourly time step. First, the loads used with the simulation-based design tool were modified to more closely match the Handbook-style load representation by inputting a single average load applied every month plus a single peak load applied for 6 hours.…”