Hierarchy classification:

1. top of the aat hierarchies
2. Objects Facet
3. Object Groupings and Systems (hierarchy name)
4. systems (equipment)
5. [systems by function]
6. HVAC
7. heating systems
8. solar heating (systems)

Anotations

Scope note:

Solar heating systems that collect and transfer heat by the natural laws of convection, conduction, and radiation with little or no mechanical assistance; for solar heating systems utilizing mechanical devices to transfer heat, use "active solar heating."