More Heat Than Light: Six Wrong Ways to Daylight a Building

Thanks to LEED and other standards, everyone's doing daylighting now--but not everyone is getting it right. Here's how it goes wrong--and how to do it right.

The Seattle Central Library has been lauded for its daylighting features, but many library patrons and staff have trouble with overheating and glare at workstations like these. Photo: Nadav Malin

You can't turn around these days without seeing a case study that mentions the use of natural daylight to help save energy and enhance the well-being and productivity of occupants--especially students and employees.

Unfortunately, almost as common are horror stories of fabulous green buildings that make their occupants miserable. Here at BuildingGreen, we've heard a tale or three about librarians wearing sun visors on the job, office workers using open umbrellas as parasols in their cubicles, and schoolteachers in award-winning buildings who keep the blinds closed constantly.

For our recent EBN feature article, "Doing Daylighting Right," we collected some of these stories, along with some really great tips from leading daylighting experts who have accomplished successful daylighting designs resulting in happy, productive building occupants and lower energy bills. But in case you're interested in how to get your daylighting design just wrong, we've put together six key tips for you below.

Overglaze it

If a little daylight is a good thing, then an all-glass building must be the ultimate, right?

Well, not so much. True design for daylighting involves intentional use of carefully chosen glazing. "There's been lots of work done by lots of people that shows that the more glass you have, the more energy you use," says Fiona Cousins, P.E., principal at Arup in New York. A 30%–40% window-to-wall ratio should provide plenty of daylight if the glass is located in the right place--high up to optimize penetration deeper into the space--Cousins adds. But if you want to forego the potential energy savings and make occupants as uncomfortable as possible, 100% curtainwall is definitely the way to go.

In seriousness, judicious use of high-performance curtainwall can be part of an energy-efficient building that still has the dazzle many designers and building owners prefer. Our research director Jennifer Atlee just put together some great guidance on standout curtainwall systems from GreenSpec and how to use curtainwalls with care.

Ignore orientation

Don't let little details like where the sun rises and sets get in the way! Looking for "connection with nature"? How about full-in-the-face glare that really gets our building occupants noticing the awesome power and life-giving force of the sun? Seeing their computer screens would only detract from this goal.

On the other hand, if you wanted to make it possible for people to work and study comfortably in their buildings, you'd end up with a lot of untidy asymmetry: shading systems that are different on the south than they are on the east or west; glazing that's "tuned" based on orientation; and clerestories or roof monitors that face north and south, never east and west.

Emphasize views and call it daylighting anyway

One of the most aesthetically pleasing ways to get daylighting wrong is to emphasize expansive views and then assume that any window area brings in useful daylight, even if the window extends all the way to the floor or is on the west orientation of the building.

A more thoughtful, occupant-focused daylighting design would separate the view windows from the daylighting windows and ensure that separate shading can be used for each. It would also provide solar shades for view windows to preserve the views while minimizing glare, relying on sophisticated modeling software to help determine the correct openness factor for such devices.

Skip the automated controls (or skimp on commissioning)

Studies have shown time and time again that you're more likely to realize energy savings from daylighting if an automatic daylight dimming system is installed in the building. One of the easiest ways to get daylighting wrong is to skip this system altogether in order to help your clients save money--or, failing that, to value-engineer commissioning of the daylight dimming system out of the budget.

If you would instead prefer to provide a workable daylighting system that will eventually pay for itself, experts agree that you'll fight tooth and nail to keep the automated controls in, and you'll work closely with the control system manufacturer, the commissioning agent, and the building owner to ensure that the system works exactly the way it should. This goes for automated shading as well.

Bump up the contrast

One of the lesser-known ways to spoil a well-designed daylighting system is through interior design. Because daylight modeling depends heavily on surface reflectance, a bold color palette can be a key part of darkening rooms, ensuring people turn on the lights more often and waste as much energy on electric lighting during daylight hours as possible. High contrast can also cause eyestrain--an emerging strategy for maximizing occupant discomfort, particularly in schools.

The lower panels in this office at the Yale Sculpture Building are filled with light-diffusing silica aerogel to provide insulation while bringing in daylight. Despite their translucence, the panels had to be covered with fiberboard in some rooms to control daylight entry. Photo: Alex Wilson

Keep occupants out of the loop

Unlike most other aspects of design, the success of daylighting depends heavily on occupant behavior, and occupant satisfaction is a key measure of success. There's nothing like a failure to communicate to really put the icing on the cake of poor daylighting performance. Occupants who don't know what interior lightshelves are for might stack books on them; occupants who don't understand how the lighting controls work might tape over the sensors; and occupants who aren't aware of the benefits of daylighting might just keep the blinds closed all the time.

In contrast, a project team trying to do good daylighting design will anticipate and design for occupant needs and habits--and will engage directly with building owners, managers, and occupants about how the lighting system works--in order to realize performance benefits from daylighting.

Doing daylighting right

If for some reason you're not satisfied with our six tips on how to do daylighting wrong and you're interested in more information on how to do it successfully, this month's EBN feature article takes a deeper look at the following issues and strategies:

• The importance of integrated design
• Preventing glare and excessive heat gain
• Balancing electric lighting with daylight
• Addressing cultural issues that make people turn on lights
• Starting space planning earlier than you might be used to
• Metrics and standards for daylighting
• Exciting innovations in wireless lighting control systems
• Guidance on daylighting products, such as lightshelves
• Integrating daylight simulations with energy models
• The importance of daylighting in everyday buildings