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Lightweight “triple-zero” house produces more energy than it uses

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NEW YORK—Overlooking the city of Stuttgart in southern Germany, a four-story modern glass house stands like a beacon of environmental sustainability. Built in 2000, it was the first in a series of buildings that are "triple-zero," a concept developed by German architect and engineer Werner Sobek, which signifies that the building is energy self-sufficient (zero energy consumed), produces zero emissions, and is made entirely of recyclable materials (zero waste).

Since the construction of the first triple-zero home, Werner Sobek’s firm of engineers and architects, based in Stuttgart, has designed and built five more in Germany, with a seventh planned in France. The energy used by these buildings, including the four-story tower where Sobek resides, comes from solar cells and geothermal heating.

The most recent addition to the triple-zero series raises the bar for energy efficiency: It produces more energy than it uses, Sobek said. The one-story glass home, which seems to float in front of a backdrop of pine trees, "is a tiny power plant [which] feeds electricity into the public grid," he said during a lecture on his work on December 2. The lecture took place at The Cooper Union for the Advancement of Science and Art.

Sobek thinks that planners, builders and policy-makers must think about how to reduce the environmental impact of buildings at the same time that they try to reduce the footprint of the automobile and other industries. The building industry is responsible for 35 percent of the world’s energy consumption and carbon emissions, and 50 percent of the waste produced in North America and Europe, Sobek said. His engineers and architects are working to reduce the energy required to maintain houses, office buildings, airports and bridges, as well the energy that goes into constructing and disassembling these structures.

Following the 1979 oil crisis, German engineers started to build "Passivhauses," or passive houses. These buildings retain comfortable interior temperatures without the use of active heating and cooling systems. Instead, passive houses receive warmth from sunlight through its south facing windows and underground air ducts in the winter, while the airtight seals prevent warm air from entering in the summer. But with the scant number of windows and 300 millimeters of thermal insulation, "you live like you are in a Styrofoam box," Sobek said.

Sobek strives for just the opposite effect of the Passivhaus, using thinner walls and bigger windows or, in the case of triple zero houses, all-glass walls. "I invented the so-called ‘Aktivhaus’ [or active house]—buildings which open your soul, which open your mind, which open your heart," said Sobek, who is also head of the Institute for Lightweight Structures and Conceptual Design (ILEK) at the University of Stuttgart and is the Mies van der Rohe professor at the Illinois Institute of Technology. These glass walls still provide insulation, however, because they are triple-glazed, meaning they have three layers of glass with air space in between the layers.

To achieve the lightweight quality of the triple-zero houses, Sobek and his architects and engineers minimize the use of steel and concrete, both of which are energy-intensive to manufacture. The carbon emissions caused by the production of cement, which is an ingredient in concrete, are greater than emissions from the aircraft industry, Sobek said. At his firm, engineers developed a technique to inject bubbles into concrete, halving the amount of concrete used, Sobek explained. The triple-zero houses also use less steel. Sobek’s home, for instance, has a thin steel frame, which includes the cables in between the glass panels.

Perhaps what truly sets the triple-zero homes apart from zero-energy buildings is how their materials are put together. Glue is avoided wherever possible because, when it comes time to take down the building, glue makes it too difficult to disassemble the materials for recycling. "[In] passive buildings, between 15 and 20 materials…are all glued together. This is nothing but a toxic waste," Sobek said. "Nobody will ever sort those materials so the result is that you put them in a waste dump and hope that the next generation will not find them."

Instead, Sobek decided that the recycling requirement for buildings should be no less than what German law decrees for the cars manufactured in its country: Ninety percent of parts in German cars must be recyclable. Borrowing the automobile’s assembly strategy, Sobek’s engineers and architects put their triple-zero houses together with stainless steel bolts, which can simply be unscrewed using wrenches. These buildings are as safe as conventional buildings, Sobek said.

While Sobek’s triple-zero houses are so far only in Germany, zero-energy buildings, which use only renewable energy—have begun cropping up in parts of the U.S., U.K. and China. Zero-energy homes in a neighborhood called BedZED, in the London Borough of Sutton, to the south of London, are made of glass and other recyclable materials and have solar photovoltaic cells that provide electricity. In Boulder, Colo., developers are planning to build 12 new zero-energy homes, which will be one of the first "eco-communities" in the country.

Image of the interior of a triple-zero building courtesy of

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  1. 1. creatorofstuff 2:03 pm 12/5/2009

    Indeed. While we are distracted with nonsensical debates over issues long ago resolved in European countries, the so-called "socialist" societies are kicking our butts in solving real problems.

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  2. 2. K.Silver 2:05 pm 12/5/2009

    Does it really matter where or who designed the buildings first? As long as the concept is out there spreading.

    Less carbon emissions, less waste, less energy consumption etc benefits the planet, the whole planet.

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  3. 3. slvrwraith 2:51 pm 12/5/2009

    Doesn’t really matter who designed/implemented it first… what matters is that we *all*, all over the world *follow suit*, quit sitting on our hands while corporate lobbies pretty much man-handle legislation… as is seen nearly every day in the hallowed halls of congress here in the US. Friggin’ foolish that, in most places in the US, you can’t install solar, wind, geothermal or even rainwater harvesting systems without jumping through 6-18 months of bureaucratic hoops, plus whatever the utility companies throw at you. Most of which costs more than the initial systems in the first place.

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  4. 4. jm666 6:25 pm 12/5/2009

    I finished building a house for a customer in North Carolina near the VA border. I installed an air core floor using a south facing glazed porch. The house was very tight and I installed an air to air heat exchanger for ventilation. A radient heat barrier in the attic finished the house and now the heat pump doesn’t run wven when there is snow on the ground. Details? email me and I an share.

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  5. 5. jerryd 10:29 pm 12/5/2009

    We have built these kind of homes here for decades, just not enough of them. Our only problems is builders don’t like doing different than they are use to and customers don’t demand them.

    You can buy some, mostly kit, manufactured homes, especially SIP where structural insulated panels/SIP are delivered and put up in a day or 2. Then just add RE depending on site and you have zero energy homes is just one example.

    I built my own for far less than the badly built home most buy.

    One can retrofit many homes with say 4" of foam insulation, better windows, doors or even build new insulating shells. It’s just not hard, just takes thinking, doing. If done right it can cost less. I’ve never figured out why people buy the car- homes out there for such high prices when they could do so much better and not only have no power bills, but a check from the power company instead!!.

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  6. 6. LarianLeQuella 1:21 am 12/6/2009

    I just wish that there were more incentives for builders to build the homes in this manner, and of course incentives for the buyers to request this. The problem for many people is that it’s much more expensive of an initial outlay than they can afford (even though they will realize cost savings in the long run).

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  7. 7. doug 1 8:05 am 12/6/2009

    Employing the characteristic German approach to efficiency and attention to detail, this seems like a natural developement and one that could lead the way internationally when integrated into mass production and begins to contribute to the power grid on a large scale. The use of geothermal is particularly promising as engineered/enhanced geothermal is starting to show promise in areas not previously thought of as having potential. Looking forward to seeing more of Herr Sobek’s designs and am interested in how the aesthetics would be expressed particularly in an urban environment.

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  8. 8. Recovering Vegetarian 9:43 am 12/6/2009

    Actually the America was the first to build passive energy efficient homes…the Germans seem to have taken it to another level.

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  9. 9. Recovering Vegetarian 9:46 am 12/6/2009

    Actually the first passive energy efficient homes were designed and built right here in the good old USA. It seems that the Germans have taken it to another level though.

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  10. 10. weingibz 2:33 pm 12/6/2009

    That’s been my dream for years. To build an energy efficient house like this. Still waiting for the building costs to come down though. Yes, it would pay for itself in energy savings, but the costs are up front.

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  11. 11. rams 4:47 pm 12/6/2009

    The technology is here and available, there is nobody keeping you from using it except the cost. Talk to your government to lower taxes and give monetary incentives to people who would like to use them.

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  12. 12. 5:41 pm 12/6/2009

    What is not clear, at least in this article, is, one: what is the ambiebnt climate? A mild climate is much easier to build in than one with extremes in summer or winter. And two, what is the structural integrity of the building under stress? Where there are prevailing occasioanl high winds, for example, how well can something that looks to be mostly glass hold up against shear forces?

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  13. 13. jaqcp 7:38 pm 12/6/2009

    Great idea for a MUSEUM PIECE or in the FREAKIN COUNTRY! Try this idea in a standard urban setting and all that glass will attract a cadre of rock-throwing teenagers and you-tube posting video-peepers/cyber-stalkers in minutes.

    I would greatly prefer 12" masonry walls (with insulation on the OUTSIDE) that will hold giga-BTUs for years AND can stop a stray 9 from a drive-by.

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  14. 14. DarthTofu 9:39 pm 12/6/2009

    Eh, I find that, while this solution would not be viable in an extreme climate (i.e. Mid-East, Parts of Canada, Siberia), the idea is very good and innovative. A town made of these houses located in the central states/parts of europe could severely reduce our use of electricity produced through nuclear and hydro power plants… not to mention the coal-burning ones.

    As for use in urban settings, just use a thick layer of plexiglass over the outside… or maybe add a 4the pane of glass on the outside, with a filling of hydrofluoric acid (or some transparent but highly-irritating substance) between it and the 3rd pane. Anyone trying to smash it would set an example as to why vandalism is not the best idea of a pastime.

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  15. 15. DarthTofu 9:39 pm 12/6/2009

    Eh, I find that, while this solution would not be viable in an extreme climate (i.e. Mid-East, Parts of Canada, Siberia), the idea is very good and innovative. A town made of these houses located in the central states/parts of europe could severely reduce our use of electricity produced through nuclear and hydro power plants… not to mention the coal-burning ones.

    As for use in urban settings, just use a thick layer of plexiglass over the outside… or maybe add a 4the pane of glass on the outside, with a filling of hydrofluoric acid (or some transparent but highly-irritating substance) between it and the 3rd pane. Anyone trying to smash it would set an example as to why vandalism is not the best idea of a pastime.

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  16. 16. scots engineer 5:47 am 12/7/2009

    The traditional alpine farmhouse was pretty efficient for it’s time. Built on three levels with the gable end southfacing with most of the windows.The lowest level housed the farm animals whose body heat, and that produced from the rotting manure, helped warm the middle level where the people lived.The top level was the hay loft which gave good insulation to the lower levels. Hay was dropped down shafts to the animals. The shallow pitch of the roof combined with some large stones spread across it kept a further layer of insulating snow until the spring thaw. All the materials would be locally grown, except the glass for the windows and metal nails, hinges etc. One way planners could help would be to give preference to designs that had a large southfacing roof in the northern hemisphere in anticipation of cheaper solar panels.

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  17. 17. Biodiversivist 1:00 pm 12/7/2009

    Some details appear to be missing. You can’t solar heat a glass house at night or when the sun isn’t shining. Even triple paned glass has very little insulation value compared to fiberglass or foam.

    When they say geothermal, are they talking about siting these homes over hot springs?

    Sometimes articles at this site read like lay press newspaper articles instead of real science.

    Something just isn’t right here. This reads like a fairy tale, all glass houses that produce more energy than they consume?

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  18. 18. Forlornehope 1:12 pm 12/7/2009

    Our house was built, or at any rate started, in 1560. It hasn’t moved much in that time so it probably has at least another 450 years in it. The roof has to be replaced every 20 to 30 years, but that’s made of water reed (thatch). I’m not sure how relevant recycling is for this kind of building. There’s more than one way to kill a cat, as the saying goes.

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  19. 19. popminer 1:27 pm 12/7/2009

    This is a great idea for architecture! My only concern is that these aren’t necessarily safe houses: would they last through heavy weather? Would they last through burglary?

    These are great houses that would improve the environment, but would they keep us safe from the environment itself?

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  20. 20. DrPhysics 3:52 pm 12/7/2009

    Before condemning the U.S. for not making these houses you might consider a few facts. First, the technologies in these houses are nothing new. Any company in the U.S. could easily take solar and geothermal technologies and then build them into a house made of recycled material. Second, and this is why they aren’t in every neighborhood in America, is what do they cost??

    You people are simply missing the point. We have the technology to make things efficient. However, we do NOT have the technology that makes it cost effective.

    The ground breaking stuff is NOT seen in these little rinky dink outfits putting together pieces of well known technology and claiming it to be revolutionary. The ground breaking work is being done in labs across the world. The day solar cells can be painted onto class for pennies is the day you’ll see a revolution. Until then this is really just eccentric b.s.

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  21. 21. Graybeard 5:09 pm 12/7/2009

    Very good, how much does it cost? Is it more than the price of an ordinary home of the same size? If so, how much energy will the difference in price buy?

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  22. 22. eco-steve 6:38 pm 12/7/2009

    Having south-facing walls made of glass is interesting. Such walls can have processor controlled and insulated wind-up blinds to control lighting and especially heat exchanges.

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  23. 23. Psmith 5:43 am 12/15/2009

    The first time that i read about this very building was over a decade ago. That text then emphasised – beside it being a ‘passive’ house, that it was a ‘cyber’ house, in the sense that it was stuffed with sensors that made sure sliding doors were closed and blinds open etc.

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  24. 24. pquerub 7:34 am 12/15/2009

    Does anyone know how much such a building costs? I can’t imagine it being "cheap."

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  25. 25. ckc1 12:54 am 01/7/2010

    Beautiful and innovative building!
    Not true that Passivhaus equals Glue and Styrofoam and limited windows. Most current Passivhaus projects use cellulose insulation and neoprene structural gaskets which can be completely disassembled and recycled. They don’t use glue or caulk to be air tight. And as window and glass technology improve it is possible to have an all glass Passivhaus, as long as shading is introduced to prevent overheating.

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