Creating Optimal Lighting Environments with a Focus on Light and Space

The lighting environment of an architectural space is an important element that dictates the comfort or impression of the space and also affects energy consumption. At Nikken Sekkei, we design lighting environments that focus not only on illuminance, which indicates the physical amount of light falling on a surface, but also “perceived brightness,” which is the actual perception of brightness in a given space.

Difficulty could be encountered in achieving spatial comfort if the design attaches importance to illuminance alone. This is because human perception of brightness in a space does not necessarily correspond to the illuminance level.
A different amount of light enters the eye from each of the various objects and surfaces making up the space, and the contrast also results in a different perception of brightness. In other words, all components making up the space we see form the lighting environment. These include not only luminaires and windows that let in natural light, but also the shape and materials of the walls, floor, and ceiling. Accordingly, attempts to brighten the space by simply increasing the amount of light or number of lighting units may not always result in enhanced perception of brightness due to the influence of contrast and surface reflectance. The affects of contrast and the amount of light entering the human eye must be studied when designing for perception of room brightness.

A lighting environment plan that takes perceived brightness into account will not only create a space with a high perception of brightness, but can also result in space designed to provide brightness contrast and a good balance between light and dark areas.

Through study of optimal perception of brightness by taking the perspective of people who occupy the space and considering the total elements that make up the space, we design lighting environments that deliver the highest level of comfort and maximum energy savings.

A task and ambient lighting system^(※) has been adopted as an effective energy-saving office lighting solution in the new Densan headquarters building. While ambient lighting achieves energy savings through low illuminance, it is also essential to have “energy savings without sacrificing comfort” by ensuring a comfortable level of perceived brightness.
This project implements a design that conserves energy and achieves a high level of perceived room brightness by efficiently increasing the amount of light entering the eye. In considering a simple approach for this, we were able to think out of the box, arriving at a plan that arranges an adequate luminance surface on a vertical plane as opposed to conventional horizontal lighting.
This design achieves substantial energy savings: energy consumption is now under 4.7W/㎡, no more than one-third of what it was before, and by incorporating daylight, a daily average of less than 4W/㎡ is consumed during the daytime.

(※)Task and Ambient Lighting System: A method that separates lighting plans into “task lighting,” which illuminates the desk, and “ambient lighting,” which illuminates the surrounding area to secure safety and perception of spatial brightness.
Energy savings become possible by separating the two functions and implementing a design that reduces the illuminance of ambient lighting and effectively enhances perceived brightness.

As an energy-saving light source, and from the aspect of its psychological benefits, daylight is certainly an effective way to achieve light. But when the lighting environment is considered, simply letting in large amounts of daylight is not necessarily the solution.
Have you ever noticed that a room appears darker because the windows are too bright?
This is the effect of contrast. Too much daylight has undesirable effects on the lighting environment. The purpose of conventional blind control was to block direct sunlight, but in a design based on the perception of brightness, controls are used to maintain good levels of daylight by preventing excessive admittance.

Using “perceived brightness images,” which depict how a person perceives brightness including contrast, many patterns were simulated over and over again in this project to study brightness perception from a variety of angles including energy, lighting environment, and design.