Overview
ISO 11479-2:2011 - "Glass in building - Coated glass - Part 2: Colour of façade" defines an objective, in situ method to evaluate the colour of coated glass as seen from the outside of a façade. The standard uses spectroscopic/colorimetric techniques (CIELAB L*, a*, b*) to quantify colour and colour differences within a single pane or between adjacent panes. It is explicitly limited to reflective colour (external appearance) at normal incidence and excludes transmitted or internal reflected colour, and curved/bent glass.
Key topics and technical requirements
- Measurement system: CIE Lab* colour space (L* = lightness, a* = green–magenta, b* = blue–yellow). Standard illuminant D65 and 10° observer referenced in Annex A.
- In situ instrumentation: Portable colorimeter or spectrophotometer used on site to measure L*, a*, b*.
- Sampling protocol:
- Minimum of three measurement points per zone (within-pane) or per pane (between-pane comparison), e.g., along a diagonal.
- Do not measure within 10 cm of an edge (or 15 cm for glass coated to fixed dimensions) to avoid edge effects.
- Comparisons only between panes of the same glass type, composition and interior conditions, and located in the same plane of the façade.
- Colour-difference calculation: ΔL*, Δa*, Δb* (simple differences between averages) and combined ΔEab calculated as the Euclidean distance in Lab space.
- Acceptance tolerances:
- ΔL* ≤ 5.0
- Δa* ≤ 5.0
- Δb* ≤ 5.0
- ΔE*ab ≤ 6.0
- Angle dependency: Colour variations with viewing angle (important for selective solar-control coatings) are acknowledged but only measurable in laboratory on small samples; ISO 11479-2 restricts field measurements to normal incidence.
Applications and who uses it
- Façade architects and designers - ensure uniform appearance across curtain walls and glazing units.
- Glass manufacturers and coaters - production quality control and batch acceptance for coated glass.
- Façade installers, contractors and site inspectors - on-site verification and acceptance testing of installed glazing.
- Specifiers and procurement teams - define objective colour tolerances in contracts and technical specifications.
- Claims resolution and forensic assessment - provide quantitative evidence for aesthetic disputes or non-conformance.
Practical benefits include repeatable, objective colour assessment for façade aesthetics, reduced subjectivity in acceptance, and an established numeric basis for procurement and dispute resolution.
Related standards
Keywords: ISO 11479-2, coated glass, façade colour, colour measurement, Lab*, ΔE, spectrophotometer, in situ colour measurement, glass in building.
