Blindly trusting the output is dangerous. Before you size a chiller or select an AHU, you need a rapid, engineering-based sanity check. While many engineers still whisper the old rule of thumb (400 sq. ft. per ton), ASHRAE Handbook—Fundamentals provides a much more accurate, albeit often overlooked, method for spot-checking results.
Open your ASHRAE Handbook—Fundamentals. In the current edition (2021/2025), Chapter 18 (Nonresidential Cooling and Heating Load) contains the gold mine: Table 9 & 10 , typically titled “Cooling Load Check Figures for Typical Commercial Buildings.” cooling load check figures ashrae pdf
We’ve all been there. You’ve spent three hours inputting walls, windows, roofs, and internal loads into your HAP, Trace, or IESVE model. The software spits out a number: 124.7 kW (35.6 tons) . Blindly trusting the output is dangerous
Suppose your calculation came back at 90 W/m² for a retail store (ASHRAE range 150–250). You are 50% low . Something is wrong. In the current edition (2021/2025)