The International Organization for Standardization (ISO) recently published a new standard on the thermal performance of curtainwall.

ISO 12631:2017, Thermal performance of curtain walling – Calculation of thermal transmittance, specifies a method “for calculating the thermal transmittance of curtain walls consisting of glazed and/or opaque panels fitted in, or connected to, frames,” according to its scope.

As noted in the document, the calculation includes:

  • Different types of glazing, for example, glass or plastic; single or multiple glazing; with or without low-E coating; with cavities filled with air or other gases;
  • Frames (of any material) with or without thermal breaks;
  • Different types of opaque panels clad with metal, glass, ceramics or any other material.
  • Thermal bridge effects at the rebate or connection between the glazed area, the frame area and the panel area are included in the calculation.

The calculation does not include:

  • Effects of solar radiation;
  • Heat transfer caused by air leakage;
  • Calculation of condensation;
  • Effect of shutters;
  • Additional heat transfer at the corners and edges of the curtain walling;
  • Connections to the main building structure nor through fixing lugs;
  • Curtainwall systems with integrated heating.

According to ISO, the standard was prepared by the European Committee for Standardization (CEN) Technical Committee CEN/TC 89, Thermal performance of buildings and building components, in collaboration with ISO Technical Committee ISO/TC 163, Thermal performance and energy use in the built environment, Subcommittee SC 2, Calculation methods. This was in accordance with the Vienna Agreement on technical cooperation between ISO and CEN.

The document, released last month, is part of a series of standards “aiming at international harmonization of the methodology for the assessment of the energy performance of buildings,” called “set of EPB standards,” according to ISO.