AS1428.1-2021- Technical article 2- Luminance Reflectance Value
Bite size technical article on AS1428.1-2021- Luminance contrast where one colour is known and you need to know what the contrasting colour needs to be, to comply with luminance contrast requirements for BCA/NCC or NDIS SDA (Specialist Disability Accommodation) requirements of SDA Design Standards for Improved Liveability.
Where LRV (Luminance Reflectance Value) of 2 (two) surfaces are known, calculating the difference in LRV is relatively simple via the Bowman-Sapolinski Equation. AS1428.1 and the SDA Design Standards state that for building elements such as doorways, a minimum of 30% luminance contrast is required between one of the following options:
- door leaf and door jamb; or
- door leaf and adjacent wall; or
- architrave and wall; or
- door leaf and architrave; or
- door jamb and adjacent wall.
If you already know LRV of one surface for example the colour of the door, determining the actual value of LRV required for the other surface such as wall or door frame to achieve the 30% luminance contrast becomes more difficult; especially when there are 2 (two) possible answers.
For example, let’s look at an LRV of 20. To achieve 30% luminance contrast with a colour of LRV 20, there are 2(two) possible options. A colour with LRV of approximately 7 or a colour of LRV of approximately 41 will both provide a luminance contrast of 30% with the colour of LRV 20 as demonstrated in the below graph (Figure B.1 of AS1428.1-2021)
To simplify the calculations of finding the LRV when LRV of one colour is known, Vista Access Architects have a new Colour Selections Calculator on the website. https://www.accessarchitects.com.au/colour-selections-calculator
Step 1: To use the calculator input any 2 (two) fields highlighted in the section below.
Step 2: Taking the same example of LRV of 20 with a 30% luminance contrast requirement, input 20 in LRV 1 section and 30% in the contrast section.
Step 3: Click on the Calculate bar and answers of both 7 and 41 are obtained because both 7 and 41 will achieve a luminance contrast of 30% with LRV of 20
It is important to note that the formula has been reverse engineered and because of the number of decimal points considered in the formula the answer will not always be accurate. We would advise aiming for a 35% luminance contrast where a minimum of 30% is required to allow for calculations and the finishes (i.e. gloss level) achieved on site.