Ask the Expert: Daylighting

Can TDDs impact funding?

As more states move from enrollment to performance-based funding systems, colleges and universities need to find ways to fuel student achievement.

Numerous studies have shown that daylight in classrooms plays an important role in student performance. Its natural brightness, variability and perfect color rendition help students stay alert, work more productively and perform better.

Yet unlike conventional daylighting options (e.g., windows and skylights), tubular daylighting devices (TDDs) deliver natural light without solar heat gain. The result is a brightly lit, comfortable learning environment that allows students and instructors to excel.

When looking for systems that bring in the most light with the least amount of heat, the light-to-solar-heat gain (LSG) ratio is a key metric. It quantifies the amount of usable light to solar heat transmitted into a space. The higher the LSG ratio, the better. A high-performing fenestration system will have an LSG ratio between 1.0 to 1.5, although recent technological advancements have resulted in breakthrough ratios of 3.0 and higher for TDDs.

Innovations prompting this include patented and proprietary daylight-collection domes, lenses and reflectors that maximize light capture and reject heat at the rooftop. Reflective tubing with integrated heat-filtering (cooling) properties further increases performance by transferring large amounts of daylight while minimizing heat gain.

Systems with daylight collectors raise the LSG ratio even higher because they capture natural light that typically bypasses the daylight collection system. In such instances, previously unattainable values nearing 5.0 are possible.

With TDDs, higher education facilities now have a viable solution that promotes student achievement and offers an advantage when it comes to performance funding.

This article originally appeared in the issue of .

About the Author

Neall Digert, Ph.D., MIES, is vice president of Product Enterprise for Solatube International, Inc., Vista, CA (