EN ISO 9920:2009 PDF

Overview

EN ISO 9920:2009 (ISO 9920:2007, Corr. 2008-11-01) - Ergonomics of the thermal environment - specifies methods to estimate the thermal insulation and water vapour resistance of a clothing ensemble. The standard treats clothing thermal characteristics under steady‑state conditions and links garment and textile data to ensemble behaviour. It was adopted as EN ISO 9920:2009 and transposed by SIST in 2010.

Key topics and technical requirements

• Scope and limits
  • Estimates resistance to dry heat loss (thermal insulation, I) and evaporative heat loss (vapour resistance) for clothing ensembles.
  • Applies to steady‑state conditions only; excludes buffering, adsorption, rain/snow effects, special active protective clothing, and separate local body-part insulation.
• Definitions and units
  • Thermal insulation defined as resistance to dry heat loss (m²·K·W⁻¹) and commonly expressed in clo (1 clo = 0.155 m²·K·W⁻¹).
• Estimation methods
  • Use of tables and measured values for known garments and ensembles (normative tables provided).
  • Procedures for calculating ensemble insulation from individual garments and for correcting small composition differences.
  • Estimation of clothing area factor and boundary air layer insulation.
• Vapour resistance
  • Methods to estimate clothing water vapour resistance from tables and from relations with dry heat resistance.
• Effects of motion and air
  • Corrections for body movement and air penetration/velocity on both thermal insulation and vapour resistance.
  • Guidance for activities other than walking and for relative air velocities.
• Annexes
  • Normative tables for ensembles, garments and vapour permeability (Annexes A–C).
  • Informative guidance on measurements with thermal manikins and human subjects (Annexes D–E) and additional explanatory material (Annexes F–H).

Practical applications and users

• Use the standard when evaluating thermal stress, thermal comfort and safety:
  • Occupational health & safety assessments (cold stress, heat stress).
  • HVAC and indoor environmental design (thermo‑ergonomics, PMV/PPD evaluations).
  • Protective clothing and PPE selection (non‑specialized garments).
  • Apparel and textile R&D for thermal performance.
  • Research using thermal manikins and human subject trials.
• Commonly applied in conjunction with thermal indices and standards such as ISO/TR 11079 (IREQ), ISO 7730 (PMV/PPD) and ISO 7933 (predicted heat strain).

Related standards

• ISO/TR 11079 - Insulation index (IREQ) for cold environments
• ISO 7730 - Thermal comfort (PMV/PPD)
• ISO 7933 - Predicted heat strain

This standard is essential for ergonomists, thermal comfort consultants, clothing designers, occupational hygienists and researchers needing consistent, validated methods to estimate clothing thermal and evaporative resistance.