ISO 7730:2025

Overview

ISO 7730:2025 - "Ergonomics of the thermal environment" - specifies an analytical method for evaluating human thermal comfort in moderate indoor environments. The standard defines how to calculate the Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) indices from measured or estimated environmental and personal parameters, and it sets local thermal comfort criteria for common causes of local discomfort. ISO 7730:2025 (fourth edition) applies to healthy men and women in work and non-work indoor spaces where thermal comfort is desirable and moderate deviations can occur.

Key topics and technical requirements

• PMV and PPD calculation: PMV predicts mean thermal sensation on the seven-point scale (hot → cold); PPD estimates the percentage likely to be dissatisfied. PMV is derived from a human heat-balance model and PPD is obtained from PMV.
• Inputs and ranges: Calculations use metabolic rate, clothing insulation, air temperature, mean radiant temperature, air velocity and water vapour partial pressure. The standard gives valid parameter ranges and notes PMV should be used for values between −2 and +2.
• Local thermal comfort criteria: Methods for predicting dissatisfaction due to draught, vertical air temperature difference, warm/cool floors, and radiant temperature asymmetry.
• Steady and non‑steady conditions: Guidance for steady-state use and for non-steady-state situations (temperature cycles, ramps, transients) including use of time‑weighted averages (previous 1 hour) for minor fluctuations.
• Calculation tools and annexes: Annex D provides a computer program for PMV/PPD; other annexes provide example requirements, metabolic rates, clothing insulation estimation (ISO 9920 referenced), humidity and air velocity guidance.

Practical applications

• HVAC design and control: set design targets for temperature, radiant conditions and air movement to meet thermal comfort objectives.
• Building performance assessment: evaluate existing offices, classrooms, factories and public buildings for occupant comfort using PMV/PPD metrics.
• Occupation health & safety and ergonomics: incorporate thermal comfort criteria into workplace risk assessments and environmental monitoring.
• Energy vs. comfort optimization: balance energy efficiency with occupant satisfaction by using PMV/PPD to inform setpoints and adaptive strategies.
• Simulation and standards compliance: apply the provided calculation methods and software to demonstrate conformity with comfort requirements.

Who should use ISO 7730:2025

• HVAC engineers and building services designers
• Architects and façade consultants
• Occupational ergonomists and safety professionals
• Facilities managers and building performance analysts
• Researchers and standards practitioners working on indoor environmental quality and thermal comfort

Related standards

• ISO 9920 - Estimation of thermal insulation and water vapour resistance of clothing
• ISO 13731 - Vocabulary and symbols (thermal environment)
• ISO/TR 23663 and ISO 28803 - complementary guidance for special populations and non‑conditioned spaces

Keywords: ISO 7730:2025, thermal comfort, PMV, PPD, ergonomics of the thermal environment, HVAC design, local thermal discomfort, operative temperature.