How to Illuminate an Interior Vertical Surface

Every area we enter surrounds us with its walls. They are building elements that limit and divide the space. In interior design, we illuminate the walls sometimes to highlight their texture and color, and sometimes the objects hanging above them. Lighting a wall adds a visual impact to space and it is typically be done by two methods; Wall Washing (WW) and Wall Grazing (WG).

Lighting vertical surfaces impact the overall illumination of a space, emphasizes the three-dimensional perception, and give environments depth. We can use wall lighting to fulfill various tasks;

• to present the wall itself alone as a surface that defines the room.
• to illuminate a room indirectly.
• to highlight objects, artworks, or the features of a wall.

Wall Washing (WW) and Wall Grazing (WG) are two similar techniques for vertical surface lighting. While WW creates visual integrity on the surface, WG aims to enhance a texture on a surface.

Therefore, the use of the two techniques varies depending on the purpose.

What is Wall Washing (WW)?

It is a lighting technique to provide uniform illumination on a vertical surface from top to bottom or vise versa. WW effect eliminates shadows and highlights the smoothness of the wall. If the goal is to accentuate features or textures, WW is not suitable because it conceals any imperfections rather than emphasizing them.

Parameters to be carefully evaluated;

• Uniformity
• Maximum coverage of light, without any dark spots between luminaires
• Minimum glare when directly viewing the luminaire
• Easy integration into the architectural ceiling design

Rules of thumb

• Mounting distance = spacing distance
• Mounting distance = 1/3 of the ceiling height

The offset from the wall should be at least one-third of the room height.

While for standard room height, the fixture spacing is the same as the distance from the wall, it should be reduced in higher rooms to compensate for lower illumination.

What is Wall Grazing (WG)?

Wall Grazing is a technique that we use to enhance a wall texture by creating shadows contrary to wall washing. We can achieve the WG effect by placing directional lights with narrow beam angles close to the wall.

Various light angles and the offsets from the wall will create soft or intense shadows, and shadows will highlight the texture.

WG applications provide non-uniform lighting distribution across vertical a surface. The results in illuminance values are highest at the light source location and lowest at the further away from the light source.

WG is not recommended for poorly designed or constructed surfaces, as it accentuates this unsightly quality.

Rules of thumb

• Mounting distance = spacing distance
• Mounting distance = never more than 30
• Avoid unsightly wall textures
• Stay away from walls with things mounted on it (unwanted shadows and glaring reflections)

The lighting vertical surfaces makes spaces appear brighter and more spacious. And it also reveals beauty by highlighting texture and creating dramatic mood and effects.

WW and WG are two lighting technics that provide different results. Therefore, the designer needs to decide what he/she wants to achieve in his/her design. Of course, whichever of these two techniques we apply; light color temperature of the light source, color rendering index, beam angle, lumen output value and the size, texture and color of the wall are factors that will determine the result.

Sources:
https://www.iguzzini.com/indoor-vertical-surface-lighting/
https://iarc.uncg.edu/elight
https://www.erco.com/guide/indoor-lighting