Daylighting—A Key Component of Energy Savings

OHSU and Mt. Angel, mentioned earlier, are not isolated examples. With its energy savings benefits, daylighting has been used effectively in sustainable buildings all over the country. In fact, in a survey of over 100 buildings saving more than 40% on their energy bills, daylighting was used by 98% of the projects.

Quite simply, the closer you get people to light generated by the sun the less energy you consume. Using natural light from the sun costs nothing to the environment but pays big dividends to building occupants. What’s more, people thrive in naturally lit environments. Studies show that office workers are more productive and absent less often, shoppers linger longer and buy more, and students do better on tests. The three biggest financial benefits of daylighting are 1) it reduces lighting costs, 2) it reduces cooling costs, and 3) it does not increase construction costs. Of course the real savings comes from turning off the electric lights, so good lighting control is a very important part of the design.

Durant Road Middle School in North Carolina was one of the American Institute of Architects “Top 10 Green Projects” in 2005. Daylighting with controls was the key design element in the LEED rated building. Energy savings from daylighting alone are 25% to 30% when compared to a conventionally built school of Durant’s size. And it was built for a lower cost than a conventional school.

At the high end, the 110,000-square-foot Alberici Headquarters Building in St. Louis, Missouri also incorporates daylighting into its LEED Platinum sustainable rebuild of an industrial plant. The optimal daylighting was achieved by reworking the façade to provide proper orientation, installing a building-wide clerestory, shading and light shelves to direct the light, automatic controls to balance daylight and electric light levels, and careful selection of glazing coefficients to block heat and glare. Energy costs have come in at or around 45% lower than a comparable conventional building.

Daylighting & Lessons Learned

After reviewing a significant number of buildings using sustainable technologies, some lessons have been learned. According to Joel Loveland, Daylighting Consultant LDL and Associate Professor University of Washington, daylighting can be best integrated into a building by observing the following ideas:

You don’t need to trade LESS building area for BETTER performance. With daylighting, the savings cover the cost.
Don’t over-glaze for daylighting. Remember: daylight is 20 times stronger than conventional fixtures. Don’t concentrate daylighting as large glass areas.
Always model the daylighting design to ensure it works as expected.
Let the building and its windows tell the story of the daylight/sunlight
Make sure the window specifications meet the use for daylighting as well as insulating
Match the daylight with where people need it most AND where they spend the most time.

Key Questions to Ask Your Daylighting Team

Developers who have used daylighting in an integrated approach to sustainable development say there are some simple questions to ask. Here are some of them:

What is the daylighting and lighting goal of your project? Can a quantitative goal be set for each type of space—labs, offices, public spaces, meeting rooms and so on?
How will you evaluate daylighting in the overall design to ensure that this project saves energy and dollars? Lighting and cooling cost impacts?
How will you simulate or model light levels to ensure the daylighting strategy works?