15.02.2017
Luminance Reflectance Values
In New Zealand there is no definitive value set on what is considered a “leading edge that can be easily seen” for access routes (NZBC – D1 Clause 1.3.3(g)) or “colour contrasted with the rest of the tread” (NZBC – D1 Clause 4.1.7). This is completely up to the building inspector, and what they personally consider to be “visually contrasting” or “easily seen”. Due to this, it is very hard to advise on what may or may not be “passable” so we refer to the Australian Building code which has set values which can be used as a guideline when selecting a colour in New Zealand.Tredsafe have carried out several LRV tests in accordance with AS1428.1 Design for access and mobility – tactile indicators Part 4.1 Appendix E was undertaken to obtain the Tredsafe insert surface Luminance Reflectance Values. All building products denoted as a surface require an LRV. The LRV is strictly a Light Reflectance measurement taken form the surface of the stated product. The results were as follows: Luminance Contrast Defined The definition of Luminance Contrast in accordance with the AS/NZS Standard 1428.1 is ‘The light reflected from one surface or component, compared to the light reflected from another surface or component’. It is not measured by the difference in the colour contrast (Background vs Foreground) but the difference in the light reflective properties of each colour. Luminance Contrast Strip (Insert) Defined The Luminance Contrast Strip provides a visual market identifying that the tread/riser intersection is evident and not obscured by similar products and colours (blending in).The strip in accordance with AS1428.1 requires a luminance contrast of at least 30% with respect to the background material or substrate.NOTE: Luminous reflectance of building elements must lie outside the shaded area. Of the 2 elements the lighter element is to be above the shaded area and the darker element is to be below the shade area.If we take our Tredsafe Neutral Black stair nosing insert with a Mean Luminance DRY value of 4.6 and locate it on the Y axis and the lighter element being the Light Grey Concrete of Mean Luminance Dry value of 31** inserted on the X axis, we find that the Black Insert on Grey Concrete substrate is well within the compliant zone (as per example shown in graph) and suitable for use in stairwells according to AS1428.1. **Mean LRV for Light Grey Portland concrete taken from figures quoted on an LRV website. Tredsafe is not responsible for testing of actual Background substrate LRV and the mean luminance value should be available from the concrete manufacturer.
