Calculating HVAC load in commercial buildings requires a few steps. First, you need to determine the total square footage of the building. This can be done by measuring the length and width of each room and multiplying them together. Next, you need to calculate the heat gain and heat loss of the building. This can be done by taking into account the insulation, windows, and other factors that affect the building’s energy efficiency. Finally, you need to calculate the total HVAC load by multiplying the total square footage by the heat gain and heat loss. This will give you the total HVAC load for the building.