Overview
ISO 7730:2005 - "Ergonomics of the thermal environment" - provides analytical methods for predicting and interpreting human thermal comfort in moderate indoor environments. The standard defines how to calculate the PMV (Predicted Mean Vote) and PPD (Predicted Percentage Dissatisfied) indices to assess overall thermal sensation and the expected proportion of occupants who will be thermally dissatisfied. It also addresses local thermal discomfort (draught, radiant asymmetry, vertical temperature gradients, floor temperatures), non‑steady‑state conditions, long‑term evaluation and human adaptation.
Key topics and technical requirements
- PMV index: Predicts the mean thermal sensation on a 7‑point scale (from −3 Cold to +3 Hot) based on metabolic rate, clothing insulation, air temperature, mean radiant temperature, air velocity and humidity. PMV is calculated from the standard equations (Clause 4) or via Annex D (computer program) and Annex E (tables).
- Validity limits: PMV should be applied mainly for PMV values between −2 and +2 and when the six main parameters lie within specified ranges (metabolic rate, clothing insulation, operative temperature, radiant temperature, air velocity 0–1 m/s, vapour pressure up to 2700 Pa - see Clause 4).
- PPD index: Derived from PMV (Equation in Clause 5) to estimate the percentage of people likely to feel too warm or too cool. The standard includes the expected distribution of individual votes for different PMV values.
- Local thermal discomfort: Procedures to predict dissatisfaction from draught, vertical air temperature difference, radiant temperature asymmetry and floor temperature (Clause 6).
- Transient and long‑term conditions: Guidance on non‑steady‑state environments (temperature ramps, cycles, transients), time‑averaging (1 hour) and long‑term evaluation and adaptation (Clauses 8–10).
- Tools and annexes: Annex D (computational program), Annex E (PMV tables), Annexes B/C for metabolic rates and clothing insulation estimation.
Applications and practical value
ISO 7730 is used to:
- Set HVAC design targets and control setpoints to achieve acceptable thermal comfort.
- Evaluate indoor environmental quality (IEQ) in offices, industrial workplaces and public buildings.
- Inform ergonomics and occupational health assessments to reduce thermal dissatisfaction.
- Support building performance evaluation, retrofit planning and occupant comfort studies by predicting percent dissatisfied and identifying local discomfort causes.
Who should use this standard
- HVAC engineers and building services designers
- Architects and façade consultants
- Occupational health & safety and ergonomics professionals
- Facility managers and indoor environmental quality specialists
- Researchers conducting thermal comfort studies
Related standards
Relevant documents referenced by ISO 7730 include ISO 7726 (measurements), ISO 8996 (metabolic rates), ISO 9920 (clothing insulation), ISO/TS 14415 (special requirements), ISO 13731 and ISO/TS 13732‑2, plus standards for extreme environments (ISO 7243, ISO 7933, ISO/TR 11079).
Keywords: ISO 7730, thermal comfort, PMV, PPD, operative temperature, local thermal discomfort, HVAC design, indoor environmental quality.
Open preview (PDF)Ergonomics of the thermal environment — Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria