5. Heat Gain from People, Lights, and Appliances
The heat given off by people, lights, and equipment represents the internal heat gain of a building.
The conversion of chemical or electrical energy to thermal energy in a building constitutes the internal heat gain or internal load of a building. The primary sources of internal heat gain are people, lights, appliances, and miscellaneous equipment such as computers, printers, and copiers (Fig. 26). Internal heat gain is usually ignored in design heating load calculations to ensure that the heating system can do the job even when there is no heat gain, but it is always considered in design cooling load calculations since the internal heat gain usually constitutes a significant fraction of it.