Heat load calculations are complicated measurements which gauge the amount of heat that is built up within a building. This calculation is then used to suggest the proper HVAC system for that building. In making the heat load calculation, a specialist will consider four main sources of heat: heat from the sun, heat from the outside air, heat from inhabitants in the building, and heat from appliances within the building.
There are multiple ways in which heat from the sun can enter the building. The most obvious way heat from the sun enters into the building is by way of radiation, that is, by sun rays shining directly into the building through the windows. There are, however, two lesser-known ways sun heat can enter. By a process known as conduction, the suns heat beating on the outside of the building enters to the inside. Finally, by way of convection, the heat from the sun on the outside air can transfer inside the building.
Another way heat from outside can enter the building is simply by way of the outside air circulating from outside to inside. Hot air will, of course, enter a building when a window or door is open, but it will also be constantly entering through the smallest of cracks throughout the building – such as those lining each door.
It may be overlooked, but one of the main sources of heat coming from inside a building is that generated from its inhabitants. Human’s naturally emit heat throughout the day, and even more so if they are engaged in physical activity. Thus, in buildings with a large number of occupants, or those where its occupants will be engaged in physical activity, a significant portion of the heat load will be generated from people themselves.
Finally, the last, and perhaps most common source of heat coming from inside a building is that generated from appliances. Practically everywhere you look inside a building will be some sort of electrical or electronic appliance: the lighting fixtures, the screens, the speakers, the kitchen appliances … the list goes on. Each of these appliances consumes electricity and, in turn, generates heat.
A specialist will consider each of the above four sources of heat – sun, outside air, inhabitants, and appliances – in their calculation to measure the amount of heat built up in the building. This calculation will then be used to suggest the proper HVAC system.