Home » Buildings »

Tubular Daylighting Offers Consistent, Natural Office Light

Sophisticated lenses and controllable dimming work together to deliver a simple result: daylight to work by. Denis Du Bois looks at the Solatube 750DS.

This is a highlight from the Building Priorities Briefing.


Denis Du Bois: ...Daylight, of course, doesn't use electricity. With the right building design, windows provide ample natural light. But many older office buildings and warehouses weren't designed to maximize daylight.
Solatube photo on EnergyPriorities.com

The Solatube 750DS uses fresnel lenses to control how much daylight enters its reflective tube, and a dimmer to control how much light is delivered to the space.

A few companies have come up with creative ways to pipe daylight from the roof into a workspace. These "tubular daylighting devices" aren't new, but their variety and sophistication is making them more attractive for certain types of facilities where windows and skylights aren't feasible.

Tubes harvest sunlight at the roof, channel it down highly reflective pipes, and deliver it to diffusers inside the building.

Solatube is one of those companies. Their tubular daylighting device, or TDD, gathers sunlight very efficiently, and gives occupants the ability to control how much daylight they get.

Solatube's flagship product is the 750DS. I asked Cynthia Sener about it at the company's Greenbuild exhibit.

It uses a Fresnel lens at the top of the tube, to capture more light, but also to sometimes capture less.

Cynthia Sener: Actually that's a good point. We were looking for a consistent light source. You have to think about your occupants. They want to rely on a daylighting system the same way they'd want to rely on electrical lights. You know, it works consistently, I don't have to worry about it, yet you want the benefits of natural light.

So we've added in some proprietary lenses into our dome, which is where it all starts, because that's where the sun is, obviously. So we have two types of lenses in our ray bender technology. We have low-angle lenses that allow you to catch morning and evening, so dawn and dusk, when it's really hard to capture the light because it's furthest out on the horizon.

Then also we have rejection lenses at the top. At really bright times of the year when the sun is directly overhead in the building, you don't want to overwhelm your occupants by having too much light. So we actually go in and minimize the high-level intensity lights and reject that, so it never even goes down the tube to deliver into a room. So we're really harnessing light when it's hard to get and rejecting light when it's overpowering.

"We are in every type of facility you can think of, from schools to retail to warehouses to logistical facilities. You name it, I've seen daylighting in it."
--Cynthia Sener, VP, Solatube.

Denis: You have these super-reflective tubes that deliver a lot of the light to the ceiling in the room where it's delivered, then you have this dimming technology at the other end...

Cynthia: We do. The way I look at it is it's three steps. You have capture, transfer, and delivery. The capture is the dome that we talked about. The transfer is that highly reflective tube. Then the delivery has so many choices. Again because the user may want to go in and turn the lights off. What if I want to have a movie in my conference room? What if I want to go to sleep in my home? There are so many options. We're in a lot of schools. Teacher needs to have the flexibility to control that light based upon what she's teaching, or he.

So we have a dimming device, and you can actually turn the light on and off to multiple different levels. Imagine it just like a dimmer you would have on electrical lighting, only it's actually blocking out the sun.

Denis: So what sort of facility is this ideal for?

Cynthia: Well, there are obvious spots, especially being here at Greenbuild. Anyone that's looking for LEED credits for their building, we actually really help buildings achieve their LEED qualifications because we qualify in so many categories. People assume that we're just in daylighting, but we're actually in a wide variety of credits across every single category of LEED. So if you're looking for sustainable design, that is a very nice sweet spot to consider daylighting. Because it really helps you get very far along the way for your LEED qualifications.

Another very obvious place is education. We see this in a lot of schools. Not only the classrooms, but the gymnasiums, the hallways, the locker rooms. You think about the time of the day that students are in class and it's when the sun's up. So it's a really obvious way to increase productivity and teacher and student happiness while they're learning. You can only use windows for so many things and they transfer a lot of heat. Our product does not. So it's a great way to have light work for schools.

But honestly we are in every type of facility you can think of, from schools to retail to warehouses to logistical facilities. You name it, I've seen daylight in it.

Denis: What if I want to add this to an existing commercial building?

Cynthia: That's actually where we tend to do more of our product installations is in retrofit. Particularly warehouse, because it's quite easy to go into an existing building and drop this product in from the rooftop. So I've seen people go in and workers will actually build all of the tubing above, cut a hole and drop it in and daylight a facility without ever affecting the workers below.

For the most part you can do it in a retrofit, as long as you have a way to deliver that light and plan around whatever else is in the ceiling plane. We have both an open ceiling and a closed ceiling application.

Closed ceiling you have to consider where your HVAC systems and other things are, but our tube can bend. So we can bend and curve around existing obstacles to get that light into the building. It's just you have to plan for it, that's all. But retrofit is very possible.

Denis: Cynthia, thanks for the tour.