Heating Loads

After we have collected all of the cooling load components for each space, the heating load is calculated. Techniques for estimating design heating loads for commercial buildings are essentially the same as those for estimating design cooling loads with the following exceptions:

• Temperatures outside conditioned spaces are generally lower than maintained space temperatures.
• Credit for solar or internal heat gains is not included
• Thermal storage effect of building structure or content is ignored.

Heat losses (negative heat gains) are thus considered to be instantaneous, heat transfer essentially conductive, and latent heat treated only as a function of replacing space humidity lost to the exterior environment. This simplified approach is justified because it evaluates worst-case conditions that can reasonably occur during a heating season. Therefore, the worst-case load is based on the following:

• Design interior and exterior conditions
• Including infiltration and/or ventilation
• No solar effect (at night or on cloudy winter days)
• Before the periodic presence of people, lights, and appliances has an offsetting effect