Technical compliance

What is Light Reflectance Value (LRV)?
Light Reflectance Value, or LRV, is a numerical scale that indicates how much visible light a surface reflects when illuminated. It’s an important metric in architecture and interior design, particularly when creating environments that are accessible to people with visual impairments. The LRV scale runs from 0 to 100, where 0 represents perfect black (absorbing all light) and 100 represents perfect white (reflecting all light). In practice, however, the brightest whites typically achieve LRVs of around 85, while the darkest blacks may only reflect about 5.

Why are Light Reflective Values important?
Visual contrast refers to how easily one element of a building can be distinguished from another, primarily based on differences in their Light Reflective Values (LRVs). While many registered blind individuals retain some level of vision—often including the ability to perceive colour—only a small proportion (less than 5%) have no vision at all, and even then, most can still detect light and shade. For those with full vision, contrast is often achieved through differences in colour type (hue) or intensity (chroma). However, for people who are blind or partially sighted, these distinctions are less effective. Instead, the key factor is how much light a surface reflects, known as its Light Reflectance Value, which plays a critical role in making elements visually distinguishable.

Light Reflective Value Requirements
When specifying door facings and ironmongery, it is important to consider differences in Light Reflective Values (LRVs) to ensure compliance with BS 8300 and Approved Document M. Approved Document M (Volume 2, Para. 0.26) defines visual contrast by stating that the difference in LRV between two adjacent surfaces should typically be at least 30 points. Where lighting levels exceed 200 lux, a minimum difference of 20 points may be acceptable. In cases where door ironmongery projects from the surface or provides additional visual definition through shadow or form, a reduced contrast of 15 LRV points can be sufficient.

For further guidance, refer to Approved Document M – Volume 2, BS 8300-2:2018 (Annex B), and Colour, Contrast & Perception: Design Guidance for Internal Built Environments by the University of Reading.

Light Refelctive Scale
The LRV scale ranges from 0 (total black) to 100 (pure white), although in practice, materials rarely reach these extremes.

The clear opening width (COW) is an essential factor in the specification of timber doorsets, particularly in settings where accessibility, fire safety, and smooth circulation are priorities. It represents the actual usable width available once a door is opened fully, typically measured from the doorstop on the latch side to the face of the open door.

This dimension is crucial for meeting UK building regulations such as Section 2 in Approved Document M,(Access to and Use of Buildings), which sets minimum width requirements to ensure wheelchair accessibility and support inclusive design. In sectors like commercial buildings, healthcare facilities, and educational environments—where frequent movement and accessibility are vital—choosing the appropriate clear opening width goes beyond regulatory compliance. It plays a key role in maintaining safety, usability, and efficient flow throughout a building.

Principal Doorsets supports compliance with Approved Document M by manufacturing doorsets precisely engineered to achieve the required clear opening widths for accessible circulation. This includes offering a wide range of door leaf sizes, frame configurations, and hinge solutions that maximise the effective clear opening, even in restricted spaces. The company provides expert guidance during specification to ensure the correct door size, swing direction, and hardware selection meet the necessary accessibility standards for wheelchair users and inclusive design. Through accurate CNC production, certified performance, and tailored project advice, Principal Doorsets helps ensure every doorset meets or exceeds Document M requirements for clear opening widths.