An Introduction to Lighting Design

Good lighting provides much more than visibility

By Nathan Dieters, PE, LC | Senior Discipline Engineer, Electrical Engineering | Honolulu Office

Lighting is an essential component of any space. Good lighting provides sufficient visibility for moving throughout a space, provides suitable light to perform specific functions, provides interest, and adapts to different uses of the space. It also aims to deliver the right amount of light and address the comfort of occupants. This article outlines the basic approach to providing good lighting design.

Approach

When you Google ‘good lighting,’ most results introduce the concept of light layering. Light layering uses multiple light sources to provide a well-lit, balanced design.  The three primary layers are 1) the ambient layer, 2) the task layer, and 3) the accent layer.

1. Ambient

The ambient layer, called ‘general’ lighting, typically consists of a uniform, symmetrical layout providing the base illuminance for a space. The ambient layer is designed for a medium to low illuminance level, targets the horizontal plane, and the source is usually selected for a medium to wide light distribution. Typical fixture selections for the ambient layer consist of troffers, linear pendants, downlights, high-bays, coves, or area lights (for exterior environments). The distribution can be direct, indirect, or indirect/direct.  Note daylighting can also provide the ambient layer instead of electric lights.

Figure 1 represents an ambient layer lighting layout for an office space. Fixtures consist of recessed 2’ x 4’ troffers, and square recessed downlights spaced uniformly and symmetrically in each space.

2. Task

The task layer is intended for a specific purpose, for example, food preparation or reading and writing. Therefore, the task layer is directed at a particular area and designed for medium to high illuminance. Typical fixture selections for the task layer consist of downlights, undercabinet lights, bathroom vanities, table lamps, pendants, or pathway lights (for exterior environments). A direct or direct/indirect distribution is typically selected.

Figure 2 represents an example of task lighting for an office desk. The task light provides a higher illuminance on the desk surface for easy reading and writing. Notice the fixture is a direct distribution focused on a relatively small area of space.

3. Accent

The accent layer is object-oriented and designed to provide contrast and intensity. It is designed for a high illuminance relative to the ambient layer and typically targets a vertical plane. Accent fixtures are almost always selected with direct distribution. Typical fixture types include adjustable (aimable) downlights, track lights, wall washers, grazers, pendants, wall sconces, and flood lights (for exterior environments).

Figure 3 represents an example of accent lighting. Wall washer lighting accentuates the textured wall and provides contrast and interest on the vertical plane.

Putting it all together

Let’s look at a lobby example showing light layers, as indicated in Figure 4. The ambient layer is provided by a combination of recessed downlights and cove lights located in the central area of the space. The accent layer is provided by a series of aim-able recessed downlights focused on artwork, indirect perimeter lights washing the vertical surfaces, and a centrally located chandelier that provides a focal point to the space. The task layer consists of recessed downlights designed to provide elevated illuminance levels at the reception desk surface.

Controls

Controls provide the adaptability of the lighting to meet the various uses of the space.  A basic rule of thumb is to provide separate control zones and dimming for each layer. Controls can transform a space into a multitude of different visual effects, such as making a space feel larger (emphasizing the accent layer), making a space feel smaller (emphasizing the task layer), or setting moods (relaxed or energizing).

Summary

My personal experience early in my career conveys the point of thoughtful lighting design. When I first started working in the architecture and engineering industry, I was tasked with providing the exterior lighting design for a bank. I selected a pole-mounted area light, modeled them at the maximum height allowed by zoning, selected a wide and bright distribution, and spaced the poles out as far as possible to achieve the illuminance criteria. I brought my design confidently to the lead engineer. During our review, the engineer (who worked for a lighting design firm) commented that while the design met the criteria, “good lighting design uses more sources with less brightness.”  That comment struck a chord with me and has stayed with me throughout my career.

We lowered the pole height to 20’-0”, selected area lights with less brightness, spaced the poles closer, used bollards at the sidewalk, and provided wall sconces flanking the building entry. I visited the site after dark when the project was complete and was impressed with how the lighting performed. It wasn’t glary; it provided the proper ambient light in the parking lot (via the pole-mounted fixtures), provided task light on the sidewalk (via the bollards), and provided accent lighting at the building entry (via the wall sconces).

Good lighting design isn’t just an engineering exercise; it’s a balancing act of engineering and art. Engineering design confirms the project meets the applicable codes and standards, and good lighting design addresses a space or environment’s aesthetics, feel, and comfort.

Learn about our Lighting Design Capabilities.