ISO 9920:2007

Overview

ISO 9920:2007 - "Ergonomics of the thermal environment - Estimation of thermal insulation and water vapour resistance of a clothing ensemble" - specifies methods to estimate the thermal characteristics of clothing ensembles in steady‑state conditions. The standard defines how to determine thermal insulation (resistance to dry heat loss) and water vapour resistance (evaporative heat loss) of garments and ensembles using measured values, tabulated data and correction procedures. It also examines how body movement and air penetration affect clothing insulation and vapour resistance. The scope excludes effects such as adsorption/buffering, rain/snow, special powered/ventilated protective clothing and local (per‑body‑part) insulation asymmetry.

Key topics and requirements

• Definitions and units for total insulation, basic (intrinsic) insulation, air (boundary) layer insulation, clothing area factor and resultant (dynamic) insulation.
• Methods to estimate ensemble insulation:
  • Using tables of measured values for garments and ensembles (normative annexes).
  • Calculations based on component garment values and adjustments for ensemble composition.
• Estimation of water vapour resistance and a vapour permeability index for ensembles.
• Procedures to correct insulation and vapour resistance for body movement, walking and other activities, and relative air velocity.
• Guidance on measurement techniques: thermal manikin testing (normative/informative annexes) and human subject measurements (informative annex).
• Annexes containing normative tables of insulation for common garments and ensembles, vapour permeability values, and measurement guidance.

Applications

ISO 9920 is a practical reference for:

• Evaluating clothing in thermal comfort and safety assessments (cold stress, neutral comfort and heat strain).
• Supporting calculations for indices such as IREQ (cold stress insulation), PMV‑PPD (thermal comfort) and predicted heat strain.
• Designing apparel and personal protective equipment (PPE) where thermal properties and breathability are critical.
• Performing laboratory testing and thermal manikin studies to characterize clothing ensembles. Use cases include occupational health risk assessment, HVAC and indoor environment design, sportswear and outdoor clothing development, and research in textile science and ergonomics.

Who uses it

• Ergonomists and occupational health professionals
• Textile and garment designers, PPE engineers
• Environmental and HVAC engineers
• Researchers conducting thermal manikin tests and human subject studies

Related standards

• ISO 7730 - Ergonomics of the thermal environment: PMV/PPD indices
• ISO/TR 11079 - Cold stress and insulation index (IREQ)
• ISO 7933 - Predicted heat strain

Keywords: ISO 9920, thermal insulation, water vapour resistance, clothing ensemble, thermal manikin, ergonomics of the thermal environment, clothing vapour resistance, clothing area factor, vapour permeability index.