ISO 10292:2026

Overview

ISO 10292:2026, titled Glass in building - Determination of thermal transmittance (U value) - Calculation method, specifies a standardized calculation approach for determining the thermal transmittance, commonly referred to as the U value, of glass used in buildings. This international standard, developed by ISO Technical Committee TC 160 (Glass in building), is tailored for glass products with flat and parallel surfaces. It covers a broad range of glass types including uncoated and coated flat glass, patterned glass, and certain specialty glass materials such as soda lime glass, borosilicate glass, glass ceramics, alkaline earth silicate glass, and alumino silicate glass. The document applies to both monolithic and multiple glazing units but excludes vacuum insulating glass (VIG) and glazing solutions incorporating far-infrared transparent spacers or interlayers.

The standard provides a calculation method rather than a measurement-based approach, enabling consistent and comparable evaluation of the thermal insulation properties of glazing used in building envelopes.

Key Topics

• Thermal Transmittance (U Value): Defines how efficiently heat is transferred through the central area of a glazing product, expressed as W/(m²·K).
• Applicable Glass Types: Includes uncoated and coated glass, patterned glass, and multiple glazing constructed from specified glass types. Specifically excludes VIG and certain multiple glazing configurations.
• Excluded Effects: Edges, spacers, frames, bars, and solar radiation transfer are outside the standard’s calculation scope.
• Calculation Components:
  • Radiative and Conductive Transfer: Considers the combined impact of radiation and gas conductance across glass layers and gas spaces.
  • Material Properties: Incorporates key glass and gas properties-such as emissivity, density, thermal conductivity, viscosity, and specific heat.
  • Standardized Boundary Conditions: Specifies reference conditions for fair product comparison, including temperatures and heat transfer coefficients.
• Declared vs. Design U Values: Declared (standardized) values can be used for comparisons, while additional parameters are available for design-specific calculations.
• Reporting Requirements: Stipulates documentation of glazing structure, material properties, and calculation details in any result or certification.

Applications

The ISO 10292:2026 standard is vital for professionals involved in building design, construction, fenestration manufacturing, and energy assessment. Key applications include:

• Product Comparison: Facilitates the selection and comparison of glazing products by providing a consistent methodology for determining U values.
• Building Energy Efficiency: Supports architects and engineers in specifying glazing units that contribute to building envelope efficiency and compliance with energy codes.
• Thermal Performance Calculations: Used as the basis for energy modeling, heat loss assessments, and condensation risk analysis.
• Certification and Labelling: U values calculated according to this standard are used in product data sheets, energy certifications, and sustainability documentation.
• Design Optimization: Allows adaptation of the calculation for glazing at different inclinations and specialized environmental conditions, supporting building-specific performance optimization.

Related Standards

When working with ISO 10292:2026, consideration of the following related standards is recommended for comprehensive building envelope assessments:

• ISO 6946: Building components and building elements - Thermal resistance and thermal transmittance - Calculation methods.
• ISO 10291 and ISO 19916-1: Methods for VIG U value determination.
• ISO 10077-1: Calculation of overall U value of windows, doors, and shutters, referencing glass U values calculated according to ISO 10292.
• ISO 15099: Detailed energy performance calculations for windows and glazing, including shading.
• ISO 20589: Determination of glass emissivity.
• ISO 9050: Determination of luminous and solar characteristics of glazing.
• ISO 10211: Detailed calculations for thermal bridges in building construction.

By following the standardized calculation method outlined in ISO 10292:2026, professionals ensure accurate, comparable, and transparent evaluation of the thermal insulation provided by glass and glazing products in buildings, supporting both product innovation and regulatory compliance in the field of building energy efficiency.