Daylighting is an environmentally friendly option that’s catching corporate interest. Many organizations, however, have limited knowledge as to its advantages and how to implement a comprehensive program. As an architect, you have several options to think about when determining what will work best in your next building project.
Passive vs. Active Controls
Passive. Windows and skylights are the most traditional, but there are many ways to implement daylighting. You can use passive control devices, such as light shelves, light reflectors, sunshades, and sunscreens, to direct, reflect, and control daylight.
Light shelves – white or reflective horizontal elements – can be installed on the inside of a window to bounce direct sunlight deeper into the space.
Daylighting Benefits
The overall objective of daylighting is to minimize the use of artificial light and reduce electricity costs, but it can also lower HVAC costs. Electrical lighting in modern buildings produces a lot of heat; if properly directed, though, natural lighting generates hardly any heat at all. In addition, the budgeted amount for electrical lighting, as well as heating or cooling loads and the amount of cooling required keeping a building at a specified temperature, can be redirected toward lighting systems and HVAC equipment.
A high-performance daylighting system may initially require a significant investment. However, if the project team uses an integrated, strategic design approach, a company’s overall long-term savings often make up for any initial dollars spent on daylighting.
For most buildings, the energy savings typically range from 15 to 40 percent. Although energy savings and sustainability may be the reasons companies initially opt for daylighting, it can have a significant, measurable impact on the productivity and satisfaction of tenants and occupants.
Even retail stores like Wal-Mart are beginning to see the benefits of daylighting for employees and consumers. In a test experiment, stores included skylights over certain departments and found that overall sales per square foot were higher in the departments that were lit by natural light.
Light reflectors share a similar purpose; however, they’re placed on the building’s exterior to direct and reflect the sun’s rays to a more useful orientation. Sunscreens and sunshades on horizontal and overhead glazing allow for maximum daylight while controlling heat and glare.
Active. A building needs active electronic control systems designed to manage and direct the level and timing of artificial light. These systems, using sensors and actuators, are directly linked to artificial lighting systems to detect the amount of daylight currently available. Then, the systems adjust the amount of artificial light provided based upon the current amount of natural light available from the sun and passive controls.
The types of lighting controls best suited for a building depends on lighting usage patterns and the type of space and a building’s layout. The use of dimmers and time scheduling are popular options for daylit offices since some workers prefer lower levels of light. Time scheduling, often used in larger, open-office areas, allows lighting to be controlled through automatic switching at fixed hours of the day.
Overcoming Daylighting Challenges
Although daylighting provides positive results, if it’s not executed properly, it can produce negative results. Below are a few strategies to help you overcome the challenges of daylighting.
Glare Control – Avoiding Direct Sunlight on Worksurfaces. Direct sunlight penetration in classrooms and office spaces produces an unpleasant glare on worksurfaces, making it difficult to work, concentrate, or view a computer screen.
The proper orientation of windows and skylights can admit sunlight and diffused daylight, producing the best combination of light for a building while reducing glare. The selection and orientation of windows and skylights should determined by the amount of energy needed, and based upon climate and building design.
Light shelves extend the penetration of sunlight into a building. Usually located above the occupied zone, these elements function to increase the effective area and diffuse incoming light. These horizontal planes bounce light upward to illuminate the ceiling. Light bouncing from the ceiling not only lights the worksurface, but makes a space appear brighter. An amplification of the longstanding practice of white ceiling surfaces, daylighting provided by light shelves enhances the quality of light. Light shelves can be incorporated into a window framing system or decorative elements supported by the building structure.
Light reflectors are more often used to aim sunlight in the proper direction. These can be as simple as reflective glazing on a nearby wall, or as complex as motorized sun tracking arrays. Often, the best application of this approach is where site or building constraints do not allow glazing to face the optimal solar orientation. Sun tracking arrays are now commercially available in a complete skylight assembly. These have proven useful in warehouse and industrial buildings where high, single-story spaces allow diffusion of daylight through distance. A more traditional application of a sunlight reflector is pools of water on the equator side of a building façade. Reflectors are most effective when used in conjunction with techniques for diffusing direct sunlight.
Light without Heat – Increasing Daylight, but Not Cooling Loads. Since the sun is such a powerful light source, it can also produce tremendous amounts of heat. If not planned properly, using natural lighting can result in undesirable heat gains; therefore, it seems almost impossible to increase the amount of light without extra heat. However, the use of window treatments, window films, and glazing can shade a window or diffuse direct sunlight, resulting in minimized heat from the sun. This can reduce cooling loads, eliminating the need for a larger cooling system, resulting in additional savings.
Proven Facts on Benefits
The Heschong Mahone Group found that office workers who are provided with a better physical indoor work environment, including daylight, an outdoor view, and better ventilation conditions, were:
- Found to perform 10- to 25-percent better on tests of mental function and memory recall.
- Less likely to report negative health symptoms.
- Found to work 6- to 12-percent faster.
According to a daylighting and work-performance study by the California Energy Commission:
- Exposure to daylight was consistently linked with a higher level of concentration and better short-term memory recall.
- Students in classrooms with the highest levels of daylight performed 7- to 18-percent higher on standardized tests.
- Students with the most daylight in their classrooms were found to progress 20-percent faster on math tests and 26-percent faster on reading tests over the course of a year.
Daylight Obstruction – Maximizing Efficiency of Wall Openings. Some architectural features, such as a roof, atrium shapes, or a building’s angles, can obstruct daylight. To prevent daylight obstruction, you can place wall openings in strategic places within the space to utilize their efficiency.
For example, if elements that can block daylight are located high in the space, they should be as far from wall openings as possible. In a plan that features open and enclosed spaces, open-space areas should be close to the wall openings. This maximizes the illumination of daylight, reflecting light deeper into the space.
The Best Implementation of Daylighting
So, what’s the ultimate solution for daylighting needs? There isn’t one answer. Each situation, depending on overall goals, budget, and building design, requires a unique plan and set of options.
Regardless of the solution that will work best for a certain building, successful daylighting depends greatly on planning and foresight.
Mike Molinski is a project manager at Vocon, an architectural and interior design firm located in Cleveland.
