Colour & Contrast / Light Reflectance Values2018-08-29T16:52:45+00:00

Colour & Contrast / Light Reflectance Values

Specification Guidelines

Colour and contrast within the built environment affects accessibility of all building users, in particular those with a visual impairment

Project Rainbow

A research project carried out by Reading University in conjunction with the Royal National Institute of Blind People (RNIB), The Guide Dogs for the Blind Association (GDBA) and ICI Paints first examined the use of colour contrast to aid navigation around the building and identified that highlighting critical surfaces and special features can provide the basis for wayfinding for visually impaired people.

The ‘Colour Contrast & Perception’ document produced by Reading University uses light reflectance values (LRVs) to measure colour and contrast in products/surfaces and determines whether or not a suitable contrast has been achieved between surfaces.

The findings from Project Rainbow identified the following:

Special Features: identified as areas that need to be highlighted to allow a building to be used effectively by visually impaired people, i.e. stair nosing, handrails and door opening furniture.

‘Special features are additional areas, smaller that critical features, that need to be highlighted to allow the building to be used more easily by visually impaired people. Such features include sanitary ware, handrails, door handles, finger plates, switches, socket outlets, and stair nosing etc, all of which should be contrasted against the background against which they will be seen. Smaller items such as these will need a greater colour difference from their surroundings in order to be identified.’

Trim: ‘Special attention is needed to those items used in an internal environment to improve the decorative appeal and overall finish of an interior. Such items, which include coving, skirting, architrave, dado rail etc, should be decorated in colours used on larger critical surfaces.’

Project-Rainbow-image1

Critical surface:

Patterned carpet and no stair nosings – staircase looks like a ramp.

Project-Rainbow-image4

Critical surface:

Plain flooring and no stair nosings – staircase looks like a ramp.

Project-Rainbow-image2

Special features:

Stair nosing are a different colour and luminance to the flooring to define step edges.

BS 8300-2:2018 and
The Building Regulations 2010: Approved Document M

British Standard BS 8300-2:2018 states that light reflectance values (LRVs) are used to assess visual contrast using the method of measurement detailed in BS 8493:2008+A1:2010. Approved Documents M (ADM) & K (ADK) directly refers to colour and contrast in the definitions section, stating:

‘Contrast visually, when used to indicate the visual perception of one element of the building, or fitting within the building, against another means that the difference in light reflectance value between the two surfaces is greater than 30 points.’

ADM then refers to Colour, Contrast & Perception – Design Guidance for Internal Built Environments, Reading University (Project Rainbow).

Light Reflectance Values (LRVs) explained

Reflectance is the proportion of light that a surface reflects compared to the amount of light that falls on the surface. An LRV is a value given to a surface to denote the amount of light reflected. Therefore, as many people with a visual impairment can perceive light and dark, LRVs are a suitable method to measure contrast.

LRVs are marked on a scale of 1 to 100 depending on the percentage of light reflected. Dark, matt and/or textured surfaces absorb a large amount of light and, therefore, have low reflectance values. On the other hand, light, glossy and/or smooth surfaces reflect the majority of light that falls on them and have high reflectance values.

Light Reflectance Scale

In order to achieve a suitable contrast between different surfaces, Project Rainbow and ADM recommend that there is at least a 30 point (not 30%) difference in the LRVs of the two surfaces.

LRV-scale-image

How to Measure LRVs

The British Standard BS 8493:2008+A1:2010 specifies the method of test to determine the light reflectance value (LRV) of different surfaces of materials, including preparation of specimens in standardised conditions and results put into a test report. All relevant Gradus products have been measured using the CIE Y value and a test report is available upon request.

Previous to this standard being published, two widely used methods of measurement had been used – the CIE L value (fluorescent light) and the CIE Y value (natural daylight), causing confusion and potentially dangerous specifications. This standard has adopted the CIE Y value as the single consistent method of measurement for LRVs that is to be used across all industries.

What the colour & contrast guidelines mean for
Gradus stair nosings:

BS 8300-2:2018 ‘Each step nosing should incorporate a permanently contrasting continuous material for the full width of the stair on both the tread and the riser to help blind and partially sighted people appreciate the extent of the stair and identify individual treads. The material should be 50mm to 65mm on the tread and 30mm to 55mm on the riser, and should contrast visually with the remainder of the tread and riser.’

ADM: ‘All nosings are made apparent by means of a permanently contrasting material 55mm wide on both the tread and the riser.’

Colour, Contrast & Perception (Project Rainbow): ‘The nosing of every step in a flight of stairs should be adequately colour or luminance contrasted with the remainder of the step and the floor coverings adjacent to the top and bottom of the flight.’