Daylighting Success Linked To Occupants

Proper planning and light placement helps architects and building owners achieve their true daylighting objectives.

Neall Digert, Ph.D., MIES, vice president of product enterprise, Solatube International Inc., Vista, CA

As human beings, we crave daylight. It heightens mood, enhances concentration, and boosts energy levels. Studies have even shown that these daylight-based benefits can increase productivity and human performance.

Just look at Pennsylvania Power & Light (1). After adding more daylight to their facility, the electric utility company experienced 13.2% higher productivity and 25% lower absenteeism. In addition, the company achieved a 69% reduction in energy costs due to decreased electricity use.

Lockheed Martin (2) saw similar results when they incorporated daylighting into a new 600,000-sq.-ft. office building. Productivity increased 15%, absenteeism dropped 15%, and lighting costs fell 75%. These are just two of many examples where daylighting positively impacted an organization.

Based on this, it’s safe to assume that most building owners would agree that daylighting has definite merits.

But what about the occupants? They’re the ones who work, learn, and spend their days inside buildings. That makes them the best judges of how effective a daylighting solution really is.

With that said, what if the daylight coming in is too overpowering? What if it creates annoying glare or shadows? What if it casts distracting patterns of light on a desk or wall that shift throughout the day? What if the sun’s heat infiltrates into the building’s interior?

Any of these scenarios could cause occupants to quickly fall out of love with daylighting. After all, it’s hard to be productive when distracted or uncomfortable.

When that happens, it doesn’t matter how effective the solution is designed. If it doesn’t meet the needs of the occupants, they will override the system to make their personal space more comfortable.

The difference between a daylighting solution that works for occupants and one that doesn’t comes down to two critical factors: proper illumination and proper placement of light.

The difference between a daylighting solution that works for occupants and one that doesn’t comes down to two critical factors: proper illumination and proper placement of light.

Design for the occupant

The key to designing a system that gets good reviews rather than constant complaints is to consider the end user.

Let’s imagine that Richard, the vice president of sales for a mid-size manufacturing company, has an office with windows running the length of one wall. While he enjoys the view of trees outside his office, the sunny glare that hits his computer screen by mid-morning forces him to close his blinds partway. This causes a portion of the room to fall into shadow. To remedy this, he turns on the electric lights so he can see his work better.

After a while, though, radiant heat from the electric lights heats up his office to an uncomfortable level. That prompts him to adjust the thermostat so the air conditioner produces colder air. Just after lunch, he notices a patch of sunlight on his desk, coming through the half open blinds. As the afternoon goes on, that patch moves along his desktop, distracting him from his work. Finally, he gives in and closes the blinds all the way, completely shutting out the daylight and his outside view.

Now let’s analyze this. Richard’s discomfort has led him to not only turn on the electric lights, but also to turn up the air conditioning. The cost savings of incorporating sustainable, energy-efficient daylight into the building has been negated and, in fact, energy use has increased. In addition, Richard is not benefiting from the daylight because he has closed his blinds by the end of the day. It’s also likely his productivity has gone down as a result of all the distractions.

Does that mean the concept of daylighting should be scrapped and we should all go back to using traditional electric lighting? Absolutely not!

Critical design factors

The undeniable benefits of daylight—lower absenteeism, greater productivity, higher performance, lower energy bills—are too significant to be ignored. Designers today simply need to be more creative in how they manage daylight through the effective use of daylighting technology.

The difference between a daylighting solution that works for occupants and one that doesn’t comes down to two critical factors: proper illumination and proper placement of light.

In decades past, windows were the most common way to bring daylight into a building. But beyond adding blinds, there was little that could be done to control the sun’s rays as they passed through the glazing. Today, new technologies like tubular daylighting devices (TDDs) make it possible to not only control how much daylight enters an interior space but also where it goes.

That means a designer can think more precisely about what he or she is trying to light and why. For example, using a TDD to illuminate a wall can make a space feel more open. It can also help reduce contrast. In fact, windows—or traditional skylights, for that matter—aren’t even needed to deliver daylight inside buildings anymore. This is great news for interior spaces lacking access to an exterior wall. TDDs can also maneuver through plenum spaces to reach locations where windows and skylights can’t even be considered.

It’s in these locations that TDDs are especially useful because they can help buildings meet mandatory code for the use of toplighting, when it’s applicable. Also, because they selectively harvest only the visible portion of the spectrum, they deliver the purest, most colorful daylight in a consistent, controlled manner.

Visual focus is crucial to enhance student learning. The needs of various classrooms are quite different from those of a university lecture hall.

Visual focus is crucial to enhance student learning. The needs of various classrooms are quite different from those of a university lecture hall.

Visual focus is key

Nowhere is this more important than in the educational environment. Here, visual focus is crucial to enhance student learning. Yet, the needs of a kindergarten classroom are quite different from those of a university lecture hall.

Keeping the attention of a class full of five-year-olds requires bright, colorful lighting that is spread evenly throughout the learning space. A university lecture hall, on the other hand, demands a different approach. Instead of uniform lighting, the objective is to draw attention to the presenter. As such, the brightest light is often directed toward the front of the room while a lower level of ambient illumination—just bright enough for note taking—is provided in the audience seating area.

If too much contrast exists between desks and the nearby wall, however, students will perceive the area as dark. TDDs with dimmers allow designers to create just the right amount of balance between different sections of the room. This lets occupants easily control the lighting atmosphere to achieve the ideal learning environment.

Complex lighting strategies

Multistory school designs create another set of challenges, requiring even more complex lighting strategies. For example, aggressive sidelighting techniques could be employed to bring daylight into a classroom—like using vision glass with a break and daylighting glazing above.

This might then be paired with indirect lighting technologies such as light shelves or light louvers to help spread the daylight evenly throughout the space. In this case, daylight comes in through the window glazing and bounces off a light shelf or louver. The daylight travels upward and reflects off the ceiling where it helps to control contrast and limit glare. It then travels down to the desktops, providing students with diffuse lighting.

Based on the daylighting rule of thumb, however, the deepest the light can enter into a room is 1 1/2 times the head height of the window. Light entering through a 10-ft.-high window, for instance, would reach about 15 ft. into the space. Since most classrooms are between 28 to 30 ft. wide, additional daylighting sources would need to be installed to light the area beyond 15 ft.

TDDs are ideal for this type of situation. When installed on the opposite side of the classroom from the windows, they eliminate shadows and create even illumination. This ensures every student receives an equal amount of daylight, no matter where they sit. To further increase the amount of light entering the space, TDDs can also be placed along the window wall. When effectively applied, a combination of daylighting design techniques can be used to artfully light the various surfaces of a room and establish a beautifully balanced space.

That balance is what promotes excellence. Whether it’s an office, a classroom, or some other interior space, occupants can attain their highest level of performance and productivity only when their environment meets their needs. TDDs are the tool that can help make that happen.


1 – Source: Seattle Times, January 18, 2000 and Architecture Week, July 2000.

2 – “Greening and the Bottom Line: Increasing Productivity Through Energy-Efficient Design,” Joseph Romm and William Browning, 1994; the non-profit Center for Energy & Climate Solutions’ Cool Companies website,, 2002.

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