ISO 29471:2008

Overview

ISO 29471:2008 establishes a standardized test method for assessing dimensional stability of thermal insulating products used in building applications under constant normal laboratory conditions (23 °C / 50 % relative humidity). The standard specifies the equipment, specimen preparation, conditioning and measurement procedures to evaluate irreversible changes in length, width and flatness of full-size products and test specimens over time.

Keywords: ISO 29471:2008, dimensional stability, thermal insulating products, 23°C/50% RH, thermal insulation testing, building applications.

Key topics and requirements

• Scope and purpose: Evaluates irreversible dimensional changes of thermal insulation materials and products subjected to normal laboratory conditions.
• Test atmosphere: Normal laboratory conditions defined as (23 ± 2) °C and (50 ± 5) % RH. Alternative tropical conditioning (27 °C / 65 % RH) may be stated in reports where relevant.
• Measurement methods: Three permitted methods:
  • Method A - linear dimensions of full-size products (use when total permitted change Δε ≥ 1 %).
  • Method B - linear dimensions on specimens smaller than full size; two variants (B1 using metal plates + dial gauge, B2 using metal wire and optical/electrical device). Use when 0.1 % < Δε < 1 %.
  • Method C - deviation from flatness for full-size products (requires 0.5 mm accuracy).
• Specimen sizes and number: Thickness must equal original product thickness. Specimen area requirements: B1 typically 500 × 500 mm (min >250 × 250 mm), B2 250 × 250 mm. At least three specimens when not testing full-size products.
• Conditioning and timing: Condition specimens ≥ 24 h before testing. Measure initial dimensions and then at standard intervals (minimum total duration 28 days with measurements at 28-day intervals). Optional additional readings at 1, 3, 7 and 14 days for finer curves. Continue until dimensional change between last two readings < 10 % of permitted total Δε.
• Accuracy and expression of results: Changes expressed as percentage for length/width and mm/m for flatness. Measuring equipment accuracy must be at least Δε/10. Repeatability ~0.4 % and reproducibility ~0.7 % (from round-robin data).
• Test report content: Must include reference to ISO 29471, product ID, pre-test history, conditioning, test method used, individual and mean results, and any deviations.

Applications

• Quality control and incoming inspection of thermal insulation boards, slabs and panels
• Product development and R&D to quantify shrinkage, swelling or warping under standard conditions
• Compliance testing for product standards, certification and regulatory documentation
• Comparative performance testing for procurement and specifications in the construction industry

Who uses this standard

• Test laboratories and certification bodies
• Manufacturers and suppliers of thermal insulating products
• Product engineers, R&D teams and quality managers in the building materials sector
• Specifiers, façade and building-envelope consultants, and procurement teams

Related standards

• ISO 29465 (length and width measurement)
• ISO 29468 (flatness measurement)
• ISO 29472, ISO 29466 and other ISO documents on thermal insulating products listed in the ISO 29471:2008 introduction

This summary helps manufacturers, test labs and building professionals apply ISO 29471:2008 for reliable dimensional stability testing of thermal insulation under standardized laboratory conditions.