SIST EN ISO 12631:2017 PDF

Overview

EN ISO 12631:2017 - Thermal performance of curtain walling - Calculation of thermal transmittance (ISO 12631:2017) specifies a standardized method to calculate the thermal transmittance (U-value) of curtain wall systems composed of glazed and/or opaque panels fitted in or connected to frames. Prepared by CEN in collaboration with ISO, this standard is part of the EPB (energy performance of buildings) set and supports consistent thermal performance assessment for façades used in building energy modelling, compliance and product development.

Key topics and technical requirements

• Scope of calculation
  • Covers curtain wall components including: glazed units (glass or plastic; single/multiple panes; low-e coatings; gas-filled cavities), frames (any material, with/without thermal breaks), and opaque panels clad with metal, glass, ceramics or other materials.
  • Includes thermal bridge effects at rebates and connections between glazed area, frame area and panel area.
• Explicit exclusions
  • Effects of solar radiation, heat transfer due to air leakage, condensation calculations, shutters, extra heat transfer at curtain-wall corners/edges, connections to main building structure or fixing lugs, and systems with integrated heating.
• Methodologies
  • Defines both a single assessment method and a component assessment method for calculating curtain wall transmittance, with prescribed input data, time intervals and reporting requirements.
• Inputs and outputs
  • Specifies geometrical characteristics, thermal properties and boundary definitions required for calculation and result presentation.
• Annexes and detailed procedures
  • Includes normative annexes (e.g., linear thermal transmittance of junctions, screw effects using ISO 10077-2 procedures, ventilated/unventilated air spaces) and templates for input and reporting.

Applications and who uses it

• Primary users
  • Façade engineers, thermal analysts, architects, product designers, window and curtain wall manufacturers, energy assessors, and certification bodies.
• Practical uses
  • Calculating a curtain wall’s U-value for building energy simulations, compliance with national energy codes and EPBD-related requirements, product development (optimizing glazing, frames, thermal breaks), tender documentation and third‑party certification.
• Benefits
  • Provides a harmonized, reproducible method for comparing systems, quantifying thermal bridge effects at junctions, and integrating curtain wall performance into whole-building energy assessments.

Related standards

• ISO 52000-1 (context of EPB modular structure)
• ISO 10077-2 (referenced for 2D numerical screw-effect procedures)
• EN ISO 12631 supersedes EN ISO 12631:2012 and forms part of the EPB standards supporting EU Directive 2010/31/EU.

Keywords: EN ISO 12631:2017, thermal performance, curtain walling, thermal transmittance, U-value, glazing, frames, thermal bridge, EPB standards.