ISO 5085-1:1989

Overview

ISO 5085-1:1989 - Textiles: Determination of thermal resistance - Part 1: Low thermal resistance specifies a steady‑state laboratory method to measure the thermal resistance (R-value) of fabrics, fabric assemblies and sheet‑form fibre aggregates with low thermal resistance (nominally up to about 0.2 m2·K/W). The procedure is intended for materials up to 20 mm thickness (edge losses become significant above this). The standard defines apparatus layout, test atmosphere, measurement methods and reporting requirements, and includes normative annexes on apparatus components, thermal conductivity calculation and example numerical values for selected textiles.

Key topics and requirements

• Scope and limits: Designed for low thermal resistance materials (≈0.2 m2·K/W; may be usable up to ≈0.4 m2·K/W); thickness limit 20 mm.
• Measurement principle: Series measurement of temperature drop across a known “standard” thermal resistance and the test specimen under steady‑state heat flow; thermal resistance derived from temperature ratios.
• Test methods: Two alternatives - the two‑plate method (preferred for accuracy and reproducibility) and the single‑plate method (for materials exposed to ambient air). Two‑plate is recommended for covered or enclosed applications (e.g., blankets under bedcovers).
• Apparatus: Hot and cold plates, insulating disc (“Standard”), temperature sensors (thermocouples), controlled cabinet with air‑flow, and insulation to limit edge losses. Annex A gives guidance on constructing/calibrating the standard resistance.
• Calibration and corrections: Procedures for calibrating the standard resistance (including use of calibrated heat‑flow discs) and accounting for contact (interface) resistance are specified.
• Conditioning and atmosphere: Tests must use ISO standard conditioning atmospheres (ISO 139): typically 65% ±2% RH at either 20 °C ±2 °C or 27 °C ±2 °C; precondition specimens (24 h).
• Units and reporting: SI unit m2·K/W; practical textile unit “tog” (1 tog = 0.1 m2·K/W). Test report must state method used, specimen resistances, mean value and conditioning details.

Applications and users

ISO 5085-1 is used for:

• Textile test laboratories and quality control teams measuring thermal insulation of clothing fabrics, blankets, quilts, carpets and insulation materials.
• Product designers and R&D teams comparing materials for thermal performance, calculating layered clothing assemblies (thermal resistances are additive), and validating simulation inputs.
• Manufacturers and specifiers requiring standardized thermal resistance data for conformity, labeling or thermal comfort assessments.

Keywords: ISO 5085-1:1989, textiles thermal resistance, low thermal resistance test, thermal conductivity, textile testing standards, guarded hot plate reference.

Related standards

• ISO 5085-2 - Textiles - Determination of thermal resistance - Part 2: High thermal resistance
• ISO 8302 - Thermal insulation - Guarded hot plate apparatus (referenced for heat‑flow methods)
• ISO 139 - Standard atmospheres for conditioning and testing textiles