ISO 10077-2:2017

Overview

ISO 10077-2:2017 - "Thermal performance of windows, doors and shutters - Calculation of thermal transmittance - Part 2: Numerical method for frames" defines a standardized numerical method to calculate the thermal transmittance (U‑value) of frame profiles and the linear thermal transmittance at frame-to-glazing or frame-to-panel junctions. The standard supplies reference input data, validation criteria for calculation programs, and guidance for treating cavities and components such as shutter profiles and roller shutter boxes. It is part of the EPB (Energy Performance of Buildings) set of standards and complements ISO 10077-1 and other energy‑performance modules.

Key topics and requirements

• Scope of calculation: Frame profile U-values, linear thermal transmittance at junctions, thermal resistance of shutters and roller-shutter components.
• Excluded effects: Solar radiation, heat transfer from air leakage, complex 3‑D heat flows (e.g., pinpoint metallic connections), and thermal bridges between frame and building structure are not included.
• Numerical methods: Supports advanced approaches including the radiosity method and a single equivalent thermal conductivity method for treating cavities; separates conduction/convection from radiation.
• Input data and parameters: Geometrical characteristics, thermal conductivity values of materials, surface emissivities, and boundary conditions. Annexes provide templates, default choices and material/property tables.
• Validation: Normative validation criteria and example cases (annexes) enable verification of calculation programs and ensure repeatable, comparable results.
• Output: Thermal transmittance (U-values), heat flow patterns and temperature fields within frames - suitable as input for whole‑window or building energy assessments.

Applications and users

• Architects and building designers seeking accurate frame U-values for energy‑efficient window and door design.
• Window, door and shutter manufacturers for product development, thermal optimization (e.g., thermal breaks) and regulatory compliance.
• Energy assessors, thermal modelers and certification bodies requiring standardized input data for EPB calculations.
• Software developers implementing validated numerical methods for frame thermal simulations.
• Regulators and code writers who reference harmonized methods in building regulations or national annexes.

Related standards

• ISO 10077-1 (whole-window thermal transmittance method) - ISO 10077-2 provides frame inputs for ISO 10077-1.
• ISO 12631 (facades and curtain walling) - covers systems outside the scope of ISO 10077.
• ISO 52000-1 (EPB modular structure) - positions ISO 10077-2 within building energy performance methodology.

ISO 10077-2:2017 is an authoritative reference for accurate, reproducible frame thermal calculations that support energy-efficient fenestration design and EPB-compliant assessments.