2.2.1 Definitions

A thermal block is a space or collection of spaces within a building having sufficiently similar space conditioning requirements so that those conditions could be maintained with a single thermal control device. A thermal block is a thermal and not a geometric concept: spaces need not be contiguous to be combined within a single thermal block.

An HVAC zone is a physical space within the building that has its own thermostat and zonal system for maintaining thermal comfort. HVAC zones are identified on the HVAC plans. HVAC zones should not be split between thermal blocks, but a thermal block may include more than one HVAC zone.

A space function is a sub-component of a thermal zone that has specific baseline lighting requirements and for which there are associated defaults for outside air ventilation, occupancy, receptacle loads, and hot water consumption. An HVAC zone may contain more than one space function. Appendix B has a list of the space functions that may be used with the COMNET rating method.

Figure 2.2.1-1 shows the hierarchy of space functions, HVAC zones and thermal blocks.

Figure 2.2.1-1: "Hierarchy of Space Functions, HVAC Zones and Thermal Blocks"