Heating & Cooling Loads5 / 13
Sources of Thermal Load
Envelope, occupancy, equipment, solar gain, and ventilation.
10 min read · Jacob Willis, Net Zero Lead · Last reviewed July 2026
An HVAC system must satisfy the thermal load of a building. The load varies with weather, occupancy, and time. Understanding where the load comes from, and what you can control, is the key to running HVAC efficiently.
In this lesson
- 01Sources of heating load (winter)
- 02Sources of cooling load (summer)
- 03Load profiles: when you actually need HVAC
- 04Key controllables
- 05Load factors: degree-days and bin analysis
- 06Sources and further reading