Section 7.1/Local Thermal Discomfort
ASHRAE 55 Section 7 covers draft risk, radiant asymmetry, vertical temperature difference, and floor surface temperature limits.
Even when the overall thermal environment is acceptable, local discomfort can occur from specific conditions. Draft risk must be limited by controlling air speed (maximum 40 fpm in cooling, higher only with occupant control). Radiant temperature asymmetry must not exceed 18 degrees F for warm ceilings, 14 degrees F for cool walls, 9 degrees F for cool ceilings, or 41 degrees F for warm walls. Vertical air temperature difference between ankle and head level (4 inches and 43 inches above floor) must not exceed 5.4 degrees F. Floor surface temperature must be between 66 and 84 degrees F.
Why this section exists
Occupant comfort depends on more than just air temperature. A person sitting next to a cold window wall, under a high-velocity supply diffuser, or above a cold concrete slab can be uncomfortable even when the thermostat reads the correct temperature. These local discomfort criteria address the most common sources of complaint that are not captured by the overall thermal comfort zone analysis.
What plan reviewers look for
Plan reviewers check supply air diffuser placement and discharge velocity to assess draft risk at occupied locations. They evaluate perimeter conditions (large glazing, uninsulated walls) for radiant asymmetry. For radiant floor heating or cooling systems, they check floor surface temperatures against the 66-84 degrees F range. These checks are most common on LEED, WELL, and high-performance building projects.
Common violations
Related ASHRAE 55 requirements
Section 5.3.1 covers the overall thermal comfort criteria. Section 5.2 covers the comfort zone graphical method. Section 8 covers long-term thermal comfort evaluation for existing buildings. ASHRAE 62.1 covers ventilation requirements that affect air speed and perceived comfort.