PMV/PPD Thermal Comfort Calculator

ASHRAE 55-2020ISO 7730
Thermal Comfort Calculator
Enter environmental and personal factors to calculate thermal comfort indices

Environmental Conditions

Dry-bulb temperature measured with shielded sensor (10-40°C)

Average temperature of surrounding surfaces (10-50°C)

Air movement speed at occupant level (0-2 m/s)

Current relative humidity percentage (0-100%)

Personal Factors

Activity level in met units (1 met = seated, quiet)

Thermal resistance of clothing in clo units

Frequently Asked Questions

Common questions about this calculator

PMV (Predicted Mean Vote) predicts average thermal sensation on a scale from -3 (cold) to +3 (hot), with 0 being neutral. PPD (Predicted Percentage of Dissatisfied) shows the percentage of people likely uncomfortable, minimum 5% even at optimal conditions.

ASHRAE 55 recommends PMV between -0.5 and +0.5, corresponding to less than 10% PPD. ISO 7730 Class A requires PPD < 6%, Class B < 10%, Class C < 15%. Most commercial buildings target Class B conditions.

Six factors: four environmental (air temperature, radiant temperature, air velocity, humidity) and two personal (metabolic rate from activity, clothing insulation). The calculator uses the Fanger model to combine all factors.

Clothing insulation is measured in 'clo' units. Light summer clothes ≈ 0.5 clo, typical business attire ≈ 1.0 clo, heavy winter clothes ≈ 1.5 clo. Higher clo values shift comfort zone to lower temperatures.

Metabolic rate measures body heat production in 'met' units. Seated quietly = 1.0 met, light office work = 1.2 met, walking = 2.0 met, heavy labor = 3-4 met. Higher activity requires cooler environments.

Individual comfort preferences vary due to physiology, acclimation, and psychology. Even at 'optimal' PMV=0, about 5% will be dissatisfied. The goal is to minimize dissatisfaction, not eliminate it entirely.