Think global, act local: How well does local thermal climatization align with current thermal comfort standards?

Local thermal comfort has attracted increased interest both from research and industry. When heating and cooling efforts are brought closer to an occupant as in the case of a Personalized Environmental Control System (PECS), the two advantages of an improved adaptability to individual preferences and a realization of energy savings are possible to achieve simultaneously. Furthermore, localized sources of discomfort can be alleviated without changes to the whole-room set-point. Yet, local climatization efforts need to be referenced against current thermal comfort standards, either to identify agreement, or to specify the need for standard revisions, if deemed necessary. In addition to this, even though current thermal comfort standards identify and provide limits for local thermal discomfort parameters individually (radiant temperature asymmetry, draught, vertical air temperature difference between head and ankles, and floor surface temperature as described in ISO EN 7730 and ASHRAE Standard 55), the occupants in buildings can be exposed to a combination of these factors simultaneously (e.g., draught and radiant temperature asymmetry from a cold window). While some effects due to local change in room conditions are already considered in these standards (e.g., higher air velocities permitted during elevated air temperatures, performance and assessment criteria for PECS), the interplay of multiple sources of discomfort is not described. Based on these two current and pressing issues, the present opinion paper suggests two development topics to be included in universal thermal comfort standards, namely interaction and combination of local thermal discomfort parameters and the applicability of the existing limits to local climatization (i.e., PECS) systems.