By knowing the construction of the structure the thermal efficiency can be calculated. This determines how much heat loss or gain is produced by the outside environment. The next step would be to determine the internal load generated by occupants and equipment.

The overall heat load would now be analyzed and the proper heating and cooling system would be selected.

Some typical problems can be solved in the above manner and all that is needed is adjustments to the existing equipment. In other cases the problem may be more complex as the shifting of heat loads due to additional equipment, such as computers that run best when kept at cooler temperatures. In these cases additional equipment may be needed or other major changes made.