BS ISO 21239-2026 PDF

Full title and description

STB BS ISO 21239-2026 — Thermal insulation products for buildings — Reflective insulating products — Specification. This designation refers to the British adoption (BS ISO) of the International Standard ISO 21239:2026, which specifies requirements for factory-made thermal insulation products incorporating one or more reflective or low-emissivity surfaces and intended to be used with an incorporated air space for building thermal insulation.

Abstract

This standard specifies requirements for reflective insulating products manufactured as rolls, boards or sheets that are intended to be used together with an air space as part of a building’s thermal insulation system. It covers product characteristics, designation and marking, and essential performance-related requirements but does not set application-specific performance levels; those are to be specified in project or regulatory documents. The standard excludes products intended for load-bearing applications.

General information

• Status: Published.
• Publication date: January 2026 (BS adoption listed as 30 January 2026).
• Publisher: International Organization for Standardization (ISO); published as BS ISO 21239:2026 for the UK market via the British Standards Institution (BSI) adoption.
• ICS / categories: 91.100.60 (Thermal insulation products).
• Edition / version: Edition 1, 2026.
• Number of pages: ISO original: 21 pages; BS-adopted publication pages may differ (commercial listings show 28 pages for the BS publication).

Scope

ISO 21239:2026 applies to factory-made thermal insulating products that contain reflective or low-emissivity surface components and are designed to work with an incorporated air space for insulating buildings. The standard covers products produced as rolls, boards and sheets and includes products used in prefabricated thermal insulation systems and composite panels where appropriate; however, it explicitly excludes prefabricated systems and composite panels from its normative scope when those assemblies require separate specifications. The standard is not intended for load-bearing insulation products.

Key topics and requirements

• Definitions and product classification for reflective/low-emissivity insulating products.
• Requirements for materials and constructions (rolls, boards, sheets) intended for use with an air space.
• Essential properties to be declared or assessed (thermal behavior in the presence of reflective surfaces, durability aspects, dimensional characteristics and permitted tolerances).
• Marking, labelling and product information required for correct selection and installation.
• Exclusions and application limits (e.g., not for load-bearing applications; does not prescribe application-specific performance levels).

Typical use and users

Typical users include building product manufacturers and suppliers of reflective insulating materials, building designers and architects specifying building envelope insulation, construction contractors and installers, testing and certification laboratories, and regulatory authorities or specifiers who set project performance criteria. The standard is used to define product characteristics and information necessary for correct selection and integration of reflective insulating products in building assemblies.

Related standards

ISO 21239:2026 is part of the body of international standards addressing thermal insulation products and building thermal performance managed by ISO/TC 163 (and specifically SC 3 for factory-made products). Users will commonly consult other national and international standards on thermal performance, fire safety, installation practices and product testing when specifying or assessing reflective insulating products.

Keywords

reflective insulation; low-emissivity surface; thermal insulation; building insulation; rolls; boards; sheets; air space; product specification; non-load-bearing.

FAQ

Q: What is this standard?

A: ISO 21239:2026 (published and adopted as BS ISO 21239:2026) is an international specification defining requirements for factory-made reflective insulating products for use in building thermal insulation systems.

Q: What does it cover?

A: It covers products with one or more reflective or low-emissivity surface components manufactured as rolls, boards or sheets and intended to be used with an incorporated air space; it sets out product definitions, required information, and essential property requirements but does not set application-specific performance levels.

Q: Who typically uses it?

A: Manufacturers, product certifiers and test laboratories, building designers and specifiers, contractors, and regulatory authorities involved in building envelope design and insulation product selection and assessment.

Q: Is it current or superseded?

A: This is a current standard published in 2026 (Edition 1, 2026). There is no indication of it being superseded as of publication.

Q: Is it part of a series?

A: It belongs to the portfolio of international standards on thermal insulation products maintained under ISO/TC 163 (factory-made thermal insulation products are within the remit of ISO/TC 163/SC 3). Users often reference other ISO and national standards on thermal performance, testing and installation alongside this specification.

Q: What are the key keywords?

A: Reflective insulation; low-emissivity; thermal insulation; building envelope; rolls; boards; sheets; air space; non-load-bearing; product specification.