What is ASHRAE 55?
ASHRAE 55 is the ASHRAE standard Thermal Environmental Conditions for Human Occupancy. It defines the combinations of temperature, humidity, air speed and radiant conditions, together with occupant activity and clothing, that a substantial majority of occupants will find thermally acceptable.
What it is
ASHRAE 55 uses six factors to describe thermal comfort: metabolic rate, clothing insulation, air temperature, mean radiant temperature, air speed and humidity. Comfort depends on all of them together, not on air temperature alone.
The standard offers methods for determining acceptable conditions, including the predicted mean vote model for mechanically conditioned spaces and an adaptive model for occupant-controlled naturally conditioned spaces. It also addresses local discomfort such as drafts, radiant asymmetry and vertical temperature differences.
Who it applies to / where it is used
ASHRAE 55 is used by HVAC designers, commissioning agents and owners of offices, schools, healthcare outpatient areas, laboratories and public buildings. Green building and wellness rating systems reference it for thermal comfort credits.
How it is measured / what evidence it needs
Design compliance is shown with calculations. In operation, comfort is checked through measurement and occupant feedback.
- Zone air temperature and humidity trends
- Air speed and radiant conditions where relevant
- Occupant surveys on thermal satisfaction
- Setpoint and schedule records by zone
How Aqueduct helps
Aqueduct maps each zone against ASHRAE 55 comfort bands and shows where comfort and energy pull against each other.
- Zone temperature and humidity at 60-second refresh through aQ AirSafe
- Comfort band views that flag zones too warm, too cool or too humid
- Setpoint adjustment where control is enabled, with owner approval
- Energy effect of comfort changes tracked through aQ EnergySmart