Daylighting is a powerful force. When a building is properly daylit, occupants feel and perform better. The environment and the building owner’s bottom line are healthier, too.
Harnessing this power requires careful design to ensure light is directed where it’s needed and the building delivers the right thermal performance to keep occupants comfortable, meet building code requirements, and manage operational expenses.
This article offers tips to strike the right balance.
Benefits of Daylighting
Daylighting has climbed on building owners’ priority lists, thanks to a growing understanding of its benefits.
“Research shows that, when a building has good daylighting, people perform better,” says Richard Braunstein, vice president of research and development for Oldcastle BuildingEnvelope. “Students’ test scores improve. Hospital patients go home sooner. Retailers’ sales rise. In office settings, productivity increases.”
Using daylighting sources can cut the electricity used for daytime lighting in half and reduce total electricity consumption by 13 percent, according to the U.S. Department of Energy. The energy needed for daytime cooling is lowered. And the savings come during daytime hours, when the demand for and cost of energy are highest.
Finally, projects seeking LEED certification can earn up to three EQ (Indoor Environmental Quality) credits.
A Holistic Approach
Daylighting should be discussed at the outset of planning, with the building owner, architects, engineers, and manufacturers all participating, says George Kolano, skylight sales manager for Oldcastle BuildingEnvelope. This enables a holistic approach to planning that encompasses everything from building orientation to how various parts of the building will be used and the daylighting options available. This helps ensure that the resulting design meets agreed-upon daylighting and performance goals while staying on budget and no one says “If only we had …” months later when making changes is time-consuming and costly.
Building Orientation and Geometry
“Building orientation and geometry are vital,” says Rick Wright, director of technical services for Oldcastle BuildingEnvelope. The building should take advantage of the sun’s angles. Natural and built structures—such as overhangs, sunshades, fixed and movable exterior louvers, and silk-screened glass—can be used to limit glare and solar heat gain.
Complementing Mother Nature
The team can then draw from a deep toolbox of products and systems to complement the building’s positioning and geometry.
A seemingly limitless array of glasses, ceramic frits, and tints are available. Generally, low-e, high-performance, double-glazed glass provide a sufficient U-factor. Commercial projects are beginning to follow the residential market’s use of two low-e coatings in the same double-glazed unit to enhance performance, Wright said.
In southern locales, a darker tint and reflective glass coatings will help manage solar heat gain. In the north, it may be appropriate to use a darker tint on southern exposures to help control summer cooling costs and a lighter tint on northern exposures to balance cooling costs and maximize visible light.
The choice of framing is also essential, Braunstein added. Effective thermal comfort, condensation resistance, and energy efficiency can only be achieved when the glass and framing solutions are in sync.
Reflected daylighting redirects light from one part of a building to another without causing glare or overheating. Options include installing light shelves on the inside of windows and including exterior sunshades or window overhangs with downward-facing reflective surfaces.
Performance Modeling Tools
Simulation apps allow architects to test daylighting system designs, helping to ensure that they will perform as expected. The architect enters details of the building’s orientation, size, geometry, and glazing features. The app factors in location and weather patterns and predicts the building’s daylighting and thermal performance. Any necessary design adjustments can then be made.
Daylighting enhances occupant performance and comfort and reduces energy consumption. Harnessing its power simply requires early planning by the broader design and construction team to tap into the array of solutions available.