ASHRAE 55 is the American Society of Heating, Refrigerating and Air-Conditioning Engineers standard that defines thermal comfort conditions for human occupancy. This standard specifies acceptable ranges for temperature, humidity, air velocity, and mean radiant temperature to maintain comfort for at least 80% of occupants in indoor spaces.
Technical Standards
ASHRAE 55-2023 establishes comfort zones between 68-76°F for winter and 74-80°F for summer at standard clothing and activity levels. The standard accounts for relative humidity between 30-60% and air velocity below 0.3 meters per second. Compliance requires documentation of design conditions, occupant activity levels, and clothing insulation values (typically 0.5-1.0 clo).
Building Applications
Compliance is mandatory for most commercial buildings, offices, schools, and healthcare facilities seeking LEED certification or meeting building codes. The standard applies to naturally ventilated, mechanically ventilated, and mixed-mode buildings with different criteria for each.
Practical Significance
Achieving ASHRAE 55 compliance improves occupant productivity and reduces complaints while justifying HVAC system investments. Non-compliance can result in regulatory violations and failed building certifications.