LET THE SUN SHINE IN — THROUGH LIGHT TUBES
Read full article by Sandra Henderson
On a recent guided tour of sustainable homes in Boulder, Colo., I had the opportunity to see first hand the incredible illumination effects of so-called light tubes. The brochure had dubbed this stop on the tour “Deep Green Remodel.” The interior of the home – even the space recessed from the windows in the front of the house – was flooded with natural light. I set out to learn more about the high-quality, daylighting effect of light tubes.
The idea of capturing sunlight through a tube is not new. The ancient Egyptians came up with the concept. Today, however, it is the modern reflective materials and advanced optics combined with the fact that light tubes use no electricity that make this technology so attractive for residential and commercial green-building projects.
Light tubes – sometimes also referred to as sun pipes or scopes, or solar light or daylight pipes – are an affordable way to bring natural light into spaces, especially deep interior spaces where skylights would not be an option. The optical technology in these daylighting systems harnesses sunlight from the roof, transfers it through mirrored tubing and effectively diffuses the light in the building interior.
As it turned out, “Deep Green Remodel” was the home – and green-building project – of Boulder Architect Ron Flax, Associate AIA, LEED AP, of Rodwin Architecture. The house was built in 1956, was 1,100 square feet and had a dreadful HERS rating of 190 before the remodel. To minimize cost and impact, Flax kept the remodel modest, only expanding the home to 1,455 square feet. He not only wanted the smaller carbon footprint inherent in a small house, he and his wife also wanted to encourage more conscious living for their family of four by intently requiring that all spaces are used to their fullest.
Among energy features like a 5.4 kW PV system that provides nearly 100 percent of the family’s annual electrical usage, a geothermal system and a high-efficiency tankless water heater, Flax describes the six lighting tubes he installed as a “splurge.”
I caught up with him to talk about the energy efficiency benefits of light tubes. “Skylights, by fact of their horizontal alignment, perform very poorly in terms of energy efficiency – a lot of heat comes in during the summer and escapes in the winter,” Flax says. “Light tubes don’t do that.”
Flax has two kinds of light tubes in his home: Two light tubes that come straight through the cathedral ceiling of the front sitting room, where traditional skylight could have been installed into the roof alternatively, and four light tubes in the interior space that is set back and does not have direct access to the roof, which would have made it impossible to install traditional skylights. “Instead, we snaked a 10- to 12-foot long light tube through the attic and out the roof, which was a fairly affordable option with very low loss of light,” Flax said.
The two types of light tubes Flax used in his own home are also the two alternatives the architect commonly uses in his projects – for daylighting, much in the same way a skylight would be used, and to bring natural light into deep interior spaces by snaking long tubes up to the roof. “We like them in closets a lot,” he said.
In the remodel of his home one-and-a-half years ago, Flax chose a daylighting product by Solartube International, as “they were the first of this style to comply with Energy Star requirements for glazing at the time,” he said.
Since then, a number of different products have come on the market. The Boulder architect explains, many light tube options now have decorative terminations to look more like light fixtures.
“The light itself is more of a cool light on the bluer side,” Flax said. While he personally likes that, he said there are now filters available to put over the terminations to soften the color of the natural light. The light from the tubes can be completely “shut off,” and dimmers and damping features are available as well. What’s more, you can choose light tubes with integrated electrical lights to use after sundown.
The benefits of light tubes are easy to see. Literally. The light-spreading systems bring sunlight into interior spaces where natural light isn’t available otherwise – at zero energy cost and with extremely low light loss. Even in spaces where traditional skylights would be an option, light tubes still offer the advantage that they don’t come with the energy penalty skylights carry. The latest systems available on the market “work well with pretty much any roofing material,” according to Flax.
By using light tubes and other energy-saving measures, Flax was able to reduce his total energy consumption and associated annual CO2 emissions by more than 90 percent. His home’s HERS score today? An impressive 5.