Incorporating shade control in lighting design strategy
Automated, integrated lighting and shade control can make buildings more efficient and occupants more productive.
- Learn how automated shading systems can help facilities reduce lighting energy use and take full advantage of updated ASHRAE Standard 90.1-2010 standards that include mandatory requirements for daylight harvesting technology.
- Compare the impact of manual shades versus automated shades as a means of achieving maximum useful daylight zones in office buildings.
- Understand the beneficial relationship between daylight harvesting and employee productivity/satisfaction.
Designing with daylight may seem revolutionary, but it is actually an ancient concept. Before the introduction of electricity, necessity drove the creative use of available daylight in building design. To illuminate interior spaces, sunny courtyards were surrounded by living space. To temper heat and glare from the sun, materials like lattice and screens were used. As electricity made it possible to light virtually any space, daylight became almost passé.
New energy regulations, increased interest in sustainability and efficiency, and a closer examination of the physiological benefits of daylight to employees and building occupants are encouraging building owners, facility managers, and lighting professionals to once again focus on daylight as an essential element to good building design.
Design trends and building codes
Lighting control strategies, and daylight harvesting in particular, have a variety of efficiency benefits including: reducing lighting energy, helping to minimize peak demand, and helping to reduce HVAC loads. One of the most powerful motivators driving daylight design in new construction and major renovation is code compliance. As utilities struggle to meet increasing demand for power, federal and state agencies are stepping in to regulate energy use.
Standards and guidelines developed by ASHRAE are now mandated by the Dept. of Energy. As of Oct. 18, 2013, all state commercial building codes must meet or exceed ASHRAE Standard 90.1-2010 that generally include mandatory requirements for daylight harvesting technology known as “Daylight Zone Control.” Other allowable building standards, such as the International Energy Conservation Code (IECC) and California Title 24, include similar daylighting requirements in their updated recommendations.
Automated lighting and shade control
A total light management system that includes automated shade control is the ideal lighting design strategy for addressing both energy and glare management. The best solutions combine automated shade control with solar-adaptive software, and cloudy-day/shadow sensors that allow the shading software to evaluate and respond to real-time daylight conditions. Keep in mind that it is important to choose a shade manufacturer that offers a broad selection of fabrics, allowing the lighting designer or architect to choose the appropriate transmittance level based on the building’s location and orientation.
By using the same lighting control system for daylight harvesting, the electric light can be used only to supplement available daylight, minimizing or eliminating lighting energy use whenever possible.
Automated shading allows the lighting system to respond to environmental factors related to both energy use and glare. As related to energy use, automated shading control works to maintain a consistent light level in all environments, and can extend the useful daylight zone (the area inside a space where enough glare-free daylight is available for daylight harvesting) inside the perimeter of the space.
Manual shades can generally achieve a useful daylight zone of 10 ft inside the perimeter windows. Because automated shades respond to real daylight conditions, they can extend the useful daylight zone to 20 ft inside the perimeter, allowing for more effective daylight control.
A study conducted by Purdue University and Lutron Electronics analyzed the benefits and energy-saving potential of solar adaptive, automated shading control systems. The study showed that perimeter private offices with daylight harvesting strategies in place can further reduce lighting energy usage by 65% through the use of automated shades. Savings were based on energy simulation of a perimeter private office with a lighting power density of 0.9 W/ft, a standard clear double-pane glass, and a shade fabric with 5% transmittance and a 76% reflectance.
Human aspects of daylight
In addition to energy-saving benefits, proper daylight design is widely acknowledged to contribute human benefits: reduced eyestrain, comfort enhancement through increased views, and circadian rhythm entrainment. These benefits work to improve mood, memory, and mental acuity, contributing to more productive buildings and building occupants—and like energy-saving benefits, they improve the bottom line. In its recently published Intersections: Health and the Built Environment, the Urban Land Institute reports a “15% potential increase in U.S. worker productivity through greater access to sunlight in office buildings.”
Quantifying the relationship between daylight harvesting and productivity has proven to be an elusive goal, but new studies show that strong correlations exist.
As noted in Greenlight New York’s Let There be Daylight: “Because the cost of employees far outweighs all other business expenses, even mild increases in productivity … can have positive financial impacts that dwarf the typical return on investment (ROI) considerations of energy conservation measures.”
The research team of Vietch, Stokkermans, and Newsham also has confirmed a significant correlation between positive lighting appraisal by employees in a space, and overall workplace satisfaction and engagement. In their study, occupants were asked to assess lighting conditions in an experimental office space. When occupants positively appraised the lighting system, they also reported the space to be more attractive, and described themselves as being in a better mood and more satisfied with their work environment. The study further concluded that there is “a connection between lighting-induced positive affect and work engagement.”
Finally, a post-occupancy evaluation of the New York Times Building in New York City by the Lawrence Berkeley National Laboratories provides excellent data that confirms significant lighting energy savings attributed to the lighting control and daylighting technologies, and also links performance to building occupants’ reaction to daylight and the quality of light in their workspaces.
According to the Energy Information Administration, lighting is responsible for almost 38% of building electricity use in commercial office buildings. Innovative lighting and shade controls can help save energy by reducing lighting energy use up to 60% or more, while also working to significantly improve the working environment.
Brian Dauskurdas is the director of Global Energy Solutions at Lutron Electronics where he has been intimately involved in the specification, construction, and commissioning of some of the largest buildings in the world. He sat on Chicago’s Construction and Real Estate Council for three years, and is currently an advisor to Realcomm’s Intelligent Building Conference.