Section 5.3.1/Thermal Comfort Criteria
ASHRAE 55 Section 5.3.1 establishes acceptable operative temperature ranges for thermal comfort based on clothing, metabolic rate, and humidity.
The acceptable operative temperature range depends on the occupant metabolic rate and clothing insulation level. For typical office conditions (sedentary activity at 1.0 met, clothing at 0.5 clo in summer and 1.0 clo in winter), the acceptable range is approximately 73-79 degrees F in summer and 68-76 degrees F in winter, assuming humidity between 30-60% and air speed below 40 fpm. The standard provides a graphical comfort zone method and an analytical method for determining acceptable conditions.
Why this section exists
Thermal discomfort is the most common indoor environmental complaint in commercial buildings. Occupants who are too hot or too cold are less productive, file more complaints, and may adjust personal heaters or fans that increase energy consumption. ASHRAE 55 provides a scientific basis for design temperatures that satisfy at least 80% of occupants, based on decades of research into human thermal physiology and subjective comfort studies.
What plan reviewers look for
While ASHRAE 55 is not typically enforced as a code requirement, some jurisdictions and green building standards (LEED, WELL) require compliance. Plan reviewers check design temperatures on the mechanical drawings against the ASHRAE 55 comfort zone. They verify that the HVAC system can maintain the specified temperature range under design load conditions and that the control strategy addresses both heating and cooling seasons.
Common violations
Related ASHRAE 55 requirements
Section 5.2 covers the comfort zone graphical method. Section 7 covers local thermal discomfort criteria (drafts, radiant asymmetry, floor temperature). ASHRAE 62.1 covers ventilation, which affects perceived air quality and comfort. ASHRAE 90.1 covers energy efficiency, which must be balanced with comfort requirements.