Section 6.1.1/Design Criteria for Occupied Spaces
ASHRAE 55 Section 6.1 covers thermal comfort design criteria including operative temperature ranges and humidity limits.
Occupied spaces must be designed to maintain conditions within the comfort zones defined by ASHRAE 55. The comfort zone depends on the metabolic rate of the occupants (sedentary office work vs. light activity), the clothing insulation level (winter vs. summer), and the combination of operative temperature and humidity. For typical office conditions (1.0 met, 0.5 clo in summer), the acceptable operative temperature range is approximately 73 to 79 degrees F with relative humidity between 30% and 60%. The standard also limits radiant temperature asymmetry, draft rate, and vertical air temperature difference.
Why this section exists
Thermal discomfort is the leading cause of occupant complaints in commercial buildings. A building that meets energy code requirements may still have uncomfortable conditions if the HVAC system creates drafts, hot spots, cold spots, or excessive humidity. ASHRAE 55 defines the specific conditions that satisfy at least 80% of occupants and provides the design criteria that HVAC systems must achieve. Many green building rating systems and building codes reference ASHRAE 55 for thermal comfort compliance.
What plan reviewers look for
Plan reviewers check the mechanical design documents for the indoor design conditions (temperature and humidity setpoints). They verify the design conditions fall within the ASHRAE 55 comfort zones for the expected activity level. They check for potential comfort issues such as large glazing areas (radiant asymmetry), overhead diffusers near occupied zones (drafts), and perimeter heating adequacy in cold climates.