Techstyle Haus Puts Hybrid Energy Future to the Test.

Posted on September 1, 2016

When we ponder the infrastructure of the future, our expectations weigh heavily on our imaginations. We know that in light of climate change and diminishing natural resources, we will have to overcome our reliance on fossil fuels. But we expect that one renewable technology, perhaps solar or wind, will dominate our design decisions. And we fear that, in acting responsibly, we may be forced to sacrifice aesthetic beauty for utilitarian efficiency.

But could the true future be both more flexible and more beautiful, defying our assumptions? Starting in 2012, Jonathan Knowles, associate professor of architecture at the Rhode Island School of Design (RISD), served as faculty advisor to a team of artists, architects and engineers determined to test their best ideas at the Solar Decathlon Europe 2014. International in scope and held in Versailles, France, the decathlon challenged contestants from 20 universities to design solar homes—structures with net zero energy consumption—that would be evaluated both for their aesthetics and their efficiency.

Knowles’ team, composed of students and faculty from RISD, Brown University, and the University of Applied Sciences of Erfurt, Germany, with support from manufacturers Viessmann, Schneider Electric, and Saint-Gobain, took an unconventional approach to an unusual contest, basing their design, not on heavy walls, but on a lightweight, fiberglass textile, and their energy requirements on a hybrid mix of renewable sources.

Textile leads to “Techstyle”

Tensile membranes have been an architectural option for decades. But Knowles’ team chose to push the figurative envelope on their literal envelope, the fiberglass and Teflon textile that served as the core of their aptly named, “Techstyle Haus.” In their design, the membrane would have to contribute to the Passive House Standard, the highest international benchmark for energy efficiency. Because the contest rules require that participating structures meet the weather and climate demands of the teams’ home locations, the Techstyle Haus, with a net floor area of 825 square feet, was designed to withstand the 130 MPH winds that can blow in Rhode Island, a coastal state within a hurricane zone. To make the challenge more interesting, and more complicated, the membrane was also turned into an energy source: flexible monocrystalline PV cells, laminated to vinyl fabric, were applied to the membranes exterior.

The resulting design, prototyped and tested in Rhode Island before it was shipped to Europe and reassembled for the contest, incorporates a three foot high “foundation” of solid bookshelves capped with another three feet of decorative textile runners; the remainder of the structure is an attractively undulant tensile membrane, contributed by Saint-Gobain, that includes a three layers of four-inch fiberglass insulation sandwiched between the exterior and interior membranes. The objective, Knowles notes, was to “tighten the envelope so that we wouldn’t lose a lot of energy; the lower the loss, the less energy needed to heat the house.”

To bring natural light into the structure, the north and south walls were fully glazed with high-performance, triple-pane, argon-filled glass windows with an R-value of 10, also manufactured by Saint-Gobain.

Viessmann contributes a coordinated, hybrid energy solution

The “guts” of the structure proved to be as innovative as its shell. Working closely with Viessmann, the Techstyle team applied a hybrid energy model that would perform efficiently under changing seasons, temperatures, and sunlight exposures. The heart of the design is a Viessmann Vitovent 300-F Heat Recovery Ventilator served by both solar thermal panels—Viessmann Vitosol 200-T evacuated tube collectors—and an air-to water heat pump, the Viessmann Vitocal 242-S.

Stephen David, Viessmann US sales director, explains the system. “It’s all intelligently coordinated,” he says, driven by temperature sensors on the solar thermal panels. “When sufficient solar is available, the panels carry the load and the heat pump is off. When there’s not enough solar, the load’s shifted to the heat pump.” With a coefficient of performance (C.O.P.) of 4, the pump is capable of extracting heat from exterior temperatures as low as 30°F.

The solar collectors, which also serve the Techstyle Haus’ domestic hot water needs via an insulated tank supplied by Viessmann, were hung on the structure’s deck railings so that the tensile membrane would not be disturbed. Unlike flat panel collectors that must be located carefully for optimal solar orientation.The evacuated tube collectors offers  “tunable” elements that can be oriented for maximum solar exposure, regardless of location, enabling the “off the membrane” design.

A winner for the future

In the contest’s “objective” categories, based on data collected over two weeks of measurements, the Techstyle Haus performed well, ranking third in overall comfort conditions. Subjectively, the Haus was a big hit with visitors. “Most of them were awestruck by the quality of light, by how quiet it was inside,” says Knowles. “Over and over they asked, ‘How do I get one of these?’”

After the contest, Techstyle Haus was reassembled at Domaine de Boisbuchet in Lessac, France, where it serves as a guest house for visiting artists-in-residence.

In its press materials, the team summarized the structure’s significance by saying, “Yes, the house works. Yes, it can be reproduced. But at its core, Techstyle Haus is a call to playful innovation and a celebration of creative thinking.”

Viessmann’s David draws a complementary conclusion. “Most of the technology we contributed to Techstyle Haus isn’t available yet in North America,” he says. “But the Techstyle Haus does point the way for our energy future. It’s not going to be about one solution, but a hybrid of many technologies—solar, photovoltaic, heat pumps, heat recovery—integrated together for one goal: smart energy consumption that’s as comfortable as it is efficient.”

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