The calculation of load for HVAC design is an important step in the design process. The load calculation is used to determine the size of the HVAC system needed to meet the heating and cooling needs of the space. The load calculation is based on the size of the space, the number of occupants, the type of construction, the orientation of the building, and the climate. The load calculation is typically done using a software program that takes into account all of these factors. The software will then calculate the heating and cooling load for the space and recommend the size of the HVAC system needed to meet the load.