Suppose your calculation came back at 90 W/m² for a retail store (ASHRAE range 150–250). You are 50% low . Something is wrong.
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. cooling load check figures ashrae pdf
Find your building type. Calculate your W/m². Compare. Adjust. Only then do you have an engineering judgement you can defend. Suppose your calculation came back at 90 W/m²
But does that feel right?
The 400 sq ft/ton Rule is Dead: How to Use ASHRAE Fundamentals to Sanity Check Your Cooling Loads you need a rapid