Dwell Magazine has an interesting article on Passive House. Click on the link below to visit their online site:

Passive Acceptance by Dwell Magazine

3 Bedroom Passive House by bere:architects of London

Two Passive Houses have won an eco-homes design competition for a sustainable development at “The Works Ebbw Vale” in Wales. The two entries, one three-bedroom and one two-bedroom house, use up to 85% less energy, emit 80% less carbon dioxide, use the sun as the primary heating source, and have excellent indoor air quality. The designs, by bere:architects of London (three bedroom) and HLM Architects of Cardiff (two bedroom), also share a commitment to regional sustainability by using locally sourced materials and products such as sheep’s wool insulation, wood pellets for biomass energy, a wildflower meadow roof, dry stacked regional stone walls, larch wood cladding, and products made by Welsh companies such as innovative cement and paper insulation. This is a great example of how Passive House can be adapted to meet regional and cultural aesthetic criteria while still providing an affordable strategy for producing ultra efficient homes.

“Using local craftsmanship, supply and materials and leading edge environmental analysis and design tools we have created a truly vernacular house reflecting the heritage of both Wales and Ebbw Vale. By applying the principles of passive design with cutting edge environmental design tools, we have designed a low energy building at affordable cost.” – Jonathan Jones, HLM Architects Regional Director

The competition houses, sponsored by the Welsh Assembly Government and Blaenau Gwent Country Borough Council in association with the Building Research Establishment (BRE), are to serve as the nucleus of a ‘Future Houses’ exhibition at the master planned redevelopment of the Ebbw Vale steel yard in Blaenau Gwent. Furthermore, the masterplan for Ebbe Vale includes a ‘Learning Campus, a Local General Hospital, a Leisure Center, Sport Pitches (playing fields), a Theater, and high quality office space all surrounded by 500 environmentally friendly homes which includes the two new Passive Houses. A strong connection to the local environment is also an essential concept of the development. As for the two Passive Houses, construction is scheduled to begin sometime in January of 2010.

2 Bedroom Passive House by HLM Architects of Cardiff

Interestingly, the requirements for the eco-homes included meeting both the German PassivHaus low carbon building standard and the Welsh Code for Sustainable Homes (CSH) Level 5 which stipulate methods for waste disposal, use of local materials, water efficiency and use of renewable energy features. In winning the competition, the design teams were able to successfully integrate the two building standards and meet their strictest requirements. This issue of competing building standards often comes up when discussing Passive House because it is being transported globally. In the U.S. for instance, the major force for green building is LEED which has its own set of unique requirements not all in tandem with the Passive House standard. The danger, beyond complicating the design and implementation processes, is that the doubling of standards reduces the major benefit of the Passive House standard, namely that it delivers a building with excellent air quality, low carbon footprint, that uses very little energy at an affordable cost.

“The innovative measures for energy efficiency used in these designs can be replicated in building developments throughout Wales and should cost no more than a standard home when economies of scale are taken into consideration. The new technologies together with the use of local products manufactured from recycled materials, open up a range of business, training and job opportunities for local people which supports our sustainable agenda.” – Leighton Andrews, Local Deputy Minister for Regeneration

The design of the houses still shows variation in the application of Passive House. Both houses are timber framed, highly insulated, nearly airtight and have glazing optimized to admit solar radiation from the south. The two storey, three bedroom, bere:architects home (shown at the top of the post) includes a thick dry stacked stone wall base with larch clad siding on the upper floor. The house is topped in a wildflower meadow roof which ties the building to the landscape. “Evacuated glass tube solar panels provide 65% of the hot water throughout the year, which is supplemented by an energy efficient gas boiler. Electricity is supplemented by Photovoltaic panels, sheep’s wool is used for interior insulation while retractable external blinds provide shade in summer.” (taken from the official BRE press release) The two storey, two bedroom, HLM Architects house on the other hand uses ” [...] PV roof tiles to supplement electricity, hot water is provided by a wood pellet biomass boiler while rainwater is harvested for gardens and flushing toilets. Movement sensors control all fixed lighting. The HLM design also features dry stone walling and uses innovative local products ranging from cement replacement from Cenin in Bridgend to paper insulation from Excel Technology in the Rhymney Valley.” (taken from the official BRE press release)

It is worth noting that these Passive Houses, and the development at large, is an indicator of the emphasis Wales is putting on sustainability. I applaud the effort and look forward to seeing images of the completed houses.

“Wales has once again shown bold environmental leadership and it will reap the commercial and employment benefits that will undoubtedly come from creating the first Passivhaus skills base in the UK. I believe that Wales now has the opportunity to become the Passivhaus centre of the UK and our practice, bere architects, looks forward to helping with this.” (taken from the official BRE press release)

No Furnaces but Heat Aplenty in ‘Passive Houses’ by the New York Times

You may also enjoy reviewing the following graphic also by the NYT:

So the question is, how did Team Germany manage to pull off a second win in this highly competitive environment? Is it nebulous ‘German precision’ or something more? It appears that Team Germany, based in a wealth of technical and architectural expertise, created a house that took most advantage of the rules and weather on the National Mall. At the same time and to the benefit of the Decathlon, Team Germany, gave the general public a peek at the next generation of plus energy houses.

The key to winning the Decathlon is, not surprisingly, the Sun. A house’s ability to collect and effectively manage solar energy is linked directly to seven of the decathlon contests, making 750 points dependent on the solar strategy. Even those contests not overtly tied to solar energy are affected profoundly by the impetus behind the competition – ‘to design, build, and operate the most livable, energy-efficient, and completely solar-powered house’. It is only natural then to see teams designing projects which react in one way or another to the sun. Pitched roofs, angled roof racks, collector facades, and many other strategies are designed to gulp as much solar radiation as possible. The benefits for teams who have excess capacity are contest winning because they are able to rack up points in contests where energy use is required. The consequences for those who do not generate enough are catastrophic as seen in the performance of teams such as the otherwise excellent Team Louisiana (full disclosure… this is my home town team).

With that in mind, Team Germany’s strategic approach to the competition, their second after winning in 2007, was to maximize their solar collection capacity – building directly on the competition’s mission and strategically paving the way for wins in several of the less conspicuous contests. In total, the house had a 11.1 kW PV system spread over about 2,200 square feet counting the entire roof and all four elevations excluding glazed southern openings and two doorways on the north and east. For the purposes of creating the most exterior surface area possible, the house nearly maximized the amount of height, width and length allowed in the competition’s guidelines. The strategy put Darmstadt out in front in terms of the sheer amount of radiation striking the building’s surface and had the added benefit of making the house, arguably, the most spacious house on the mall.

Team Germany’s tactic did not stop there however. Based on past experience from the 2007 Decathlon and planning for buildings in dubiously ’sunny’ Germany, the team chose to risk some PV efficiency in an effort to prepare for stormy weather. As their design manual states, the German designers were able to imagine, backed up by experience and analysis, a scenario where the Solar Decathlon turned into the Rainy Decathlon and make design decisions to suit. Specifically, this meant that Team Germany put their 40, 18% efficient, single-crystalline roof mounted PV panels at 0°, which amounts to a sacrifice in collection energy of 16%. The roof mounted panels are most efficient at absorbing direct sunlight so this amounts to a major sacrifice on sunny days. The tradeoff is that with no angled roof panels, the exterior walls can come up that extra distance to the allowed 14′, a gain of two to three feet on all sides of the house. Taking advantage of the extra exterior wall area, Team Germany mounted nearly 250 thin film Copper Indium Gallium Diselenide (CIS) PV panels on the vertical facades. Thin film is not nearly as efficient as crystalline PV panel technology, only 11% efficient, but can absorb a significant amount of energy during diffuse light conditions. The two types of PV work hand in hand on the Darmstadt house. The roof slurps sunlight when the sun is shining, and the facades sip diffuse radiation when it is cloudy. The strategy allows the house to generate energy during both conditions with one technology offsetting the limitations of the other.

It is to Darmstadt’s credit that they were able to imagine and design for multiple weather conditions. All the houses do this in one way or another, but the German house takes the approach to a new level. Luckily for Team Germany the weather turned out to be awful for a good portion of the week which gave them a significant advantage over other houses. As for my home town team of University of Louisiana at Lafayette, I can only guess that their energy balance analysis did not take into account an extended period of rain. Such conditions are very unusual in Louisiana and maybe that accounted for the ill preparedness. In the end Germany generated nearly three times the amount of energy needed to run the home and used that wealth of electricity to shine in a number of contests.

At the same time, all of this photovoltaic equipment comes at a high price, as noted on Elizabeth Evitts Dickenson’s blogpost, Solarama!, in Metropolis. The final cost bracket for Team Germany is over $850,000 which makes it impractical to implement on a large scale. Darmstadt presents a compelling vision for the future, but at this time another solution is needed to affect widespread change. One clear example is the University Illinois. Their home was built for around $300,000 and just barely lost the competition. Interestingly, both Germany and Illinois designed their house to meet Passive House standards (Illinois actually received certification through PHIUS).

So is it feasible or ethical to clad all our new ‘energy plus’ buildings in photovoltaics? Maybe so. Maybe not. But it is a good way to win a Solar Decathlon. We should all design this cunningly so that our own projects perfectly suit the ‘rules’ of our local environments.

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

(above) exterior rendering by Karin Adalbert

Villa Åkarp is a positive net energy house (plusenergihus in Swedish) being built outside of Malmo, Sweden. The house, brainchild of doctor of building physics, Karin Adalberth, will generate more energy on an annual basis than it consumes by combining energy conservation, energy recovery and energy generationtechnologies, an amazing feat given that Sweden is hardly known for gratuitous solar energy. Improvising to find a solution, the designer created a partnership with local ‘green’ utility company, E.On, so that the house can purchase energy in the long dark winter months and sell electricity back to the grid during sunny (energy intense) summer months, maintaining a positive net energy ratio with the grid. The project illustrates distributed energy production and individual building energy efficiencies’ potential to revolutionize the energy industry.

Partnerships, an important aspect of groundbreaking projects such as this, are a hallmark of the villa project. The official list of collaborators includes primeproject(construction), roxull (insulation), elitfonster (windows), exoheat (solar panels), rec indovent (mechanical system), benders (roof), airglass (aerogel insulation), andaquapanel (cementboard) to name a few. Oftentimes teaming with product manufacturers and service providers affords experimental projects such as this an advantage through using cutting edge materials and strategies. In the case of Villa Akarp, sophistication and performance is certainly achieved using advanced materials, but even more important is the integrated design process which ties all the disparate elements together into a super efficient, energy producing, home.

(above) first floor plan

(above) second floor plan

The villa uses a variety of strategies to achieve excellent energy performance, but it must be noted that the design is as dependent on time-tested, traditional building, strategies as it is on high-end technological or material solutions. Dr. Adalberth lists eight strategies on the project website: 1) insulation, 2) ventilation with heat recovery, 3) low infiltration, 4) collect heat, 5) collect electricity, 6) guarantee heat generation in the wintertime, 7) install water saving devices and fixtures, 8 ) install electricity efficient devices and systems. You will notice that the project parameters are particular to a Scandinavian climate as it puts the strong emphasis on heating and none cooling. Adapting this project to a more temperate climate would mean changing some of the strategies, but the basic strategies of energy conservation, recovery and generation would still hold true regardless of location.

Insulation

The integrity of the building envelope is a crucial design element in Villa Akarp. The walls and roof have a total of 5.5 decimeters of insulation with an overall U-value of 0.08 w/m2. Karin notes that in Sweden a badly insulated wall with only 1 decimeter of insulation has a U-value of 0.5 w/m2 and that the difference could save a family 75% in energy costs for a typical house. Roxull mineral wool fiber was used throughout the house, inserted between wood framing members, because of its excellent insulation and fire resistance properties. In addition insulation, a continuous infiltration barrier was installed to prevent energy transfer due to air movement. The result is a well insulated, tight envelope that does not unnecessarily shed energy.

(above) Karin Adalbert shows off the house insulation (ROXULL); photo by Lars Bartas

The continuity of the envelope was maintained well beyond the fundamental wall assembly. Windows and doors were designed to reduce energy transfer and air leakage. The front door uses a vestibule to control the air as occupants enter or leave the dwelling. A special slues system on the door prevents air from exchanging with the exterior. Windows are high U-value triple glazed units which are deployed sparingly to bring in the maximum amount of natural light without compromising the efficiency of the envelope.

(above) Karin shows off the triple glazed fenestration; photo by Marin Lindeborg

The foundation is also well insulated as can be seen in the sketch below. The reinforced concrete slab is insulated by expanded foam insulation to the tune of 4 decimeters below and 2.5 decimeters on the perimeter. I don’t recall seeing a more robustly insulated slab in any building section.

(above) section detail of the foundation edge insulation; grafik by Krister Kronkvist

Heating

The house is based on the concepts of Passiv Haus and so can generate much of its heating from energy that is already being generated in the house itself. Bodyheat, lighting, refrigerators, computers and many other things generate heat within the house and can go a long way to preconditioning the house before designers need to bring true ‘heating’ systems online to cover the difference. The heating system itself includes an 18 m2 solarthermal collector, an accumulator tank (the heart of the building – a big circle in the first floor plan), and traditional radiators. The solar thermal system both heats the house and (pre)heats the domestic hot water. The 2,000 liter accumulator tank (storage tank) retains enough heat for use during the evening and mornings while a connected fuel pellet heater is used to heat the house’s radiator and domestic hot water during the winter or any other time the solar thermal system cannot meet demand.

A particularly innovative system uses the tempered sanitary lines exiting the house to preheat the incoming water lines to help reduce the amount of energy needed to bring the cold exterior water up to usable temperatures.

(above) water / sanitary line heat exchanger

Solar Panels and Energy Balance

32 square meters of solar panels are used to produce energy for the house. Of course, because this is Sweden (I don’t mean to knock the weather but since I am Swedish I am just being realistic… the weather is hardly Mediterranean), the solar panels are used primarly between April and October. The calculated energy balance is 4,000 kwh sold back to the grid and 2,600 kwh purchased annually, leaving a net positive energy balance. The extra energy purchased is ‘green’ so the house also has a minimal carbon footprint.

Villa Åkarp is a terrific example to architects, clients and builders out there about what can be done to increase energy efficiency, improve occupant comfort, and reduce green house gas emissions. The house cost is estimated to be almost $100,000 more than a traditional home, but I suspect a disproportionate amount of that costs is going to pay for solar panels, an item that should be seeing significant cost reductions in the future as production becomes more efficient. The basic strategy of using energy conservation, energy recovery and energy generation technologies applies to all buildings. Congratulations to the team and especially Karin Adalberth for challenging the rest of the design community to make better buildings.

For more information please visit the official Plusenergihus website.

Om du kan forsta svenska spraket ar du valkommen at kolla pa “Energihus kapar elkostnaden helt” fran SVT

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

Energy Recovery Ventilation (ERV) refers to the recapture of energy typically lost through the building ventilation process. Conditioned air that is routinely being exhausted from both residential and commercial buildings contains significant energy in the form of heat or coolth and humidity which is lost into the exterior environment. As part of a preconditioning process, ERV systems transfer the energy from the exhaust into the incoming air stream, which can also be described in terms of enthalpy. The use of ERV can have significant benefits both directly and indirectly in terms of energy efficiency, indoor air quality, and downsizing of the remaining HVAC equipment.

It is important to note the difference between Energy Recovery Ventilation (ERV) and Heat Recovery Ventilation (HRV). ERV exchanges both temperature and humidity between the exhaust and incoming air. HRV only exchanges thermal energy. The difference can also be stated as Total and Sensible or just Sensible energy exchange.

ERV systems are gaining popularity for a number of reasons. First, the technology and manufacturing processes are making the systems more affordable. Secondly, increased awareness of energy efficiency and sustainability both for environmental and economic reasons are causing more building operators to request such energy saving measures. Last and perhaps significant, increased ventilation to prevent Sick Building Syndrome (SBS) and promote healthy indoor environments results in a dramatic rise in energy consumption. Heavy ventilation or air changes requires the use of ERV technology, especially in the case of Passive Houses, high LEEDcertifications and most high performance buildings. In the United States ventilation standards are set by ASHRAE 62 which are used for both LEED and a general standard for high performance buildings. There is a growing body of data to suggest the health benefits of healthy indoor environments and updates to ASHRAE 62 are a recognition of that evolution.

An Opinion on ERV

ERV technology will likely develop further as awareness of occupant health, environmental sustainability, and energy cost grows. Right now we can recover up to 85% of the energy from the exhaust air, maybe in the future it will be possible to recapture even more. Costs will be reduced. The systems will be easier to integrate.

But to me the most exciting aspect of ERV technology is the idea that we can harvest latent, waste energy from our buildings, systems, occupants and environment. Renewable energy sources do roughly the same thing except they recover energy from the largest system of all, the planet itself. Wasting renewable energy supplies is unwarranted but probably inevitable. Entropy will occur in a system, but blatant waste of energy we have already generated elsewhere is shameful. Buildings use energy generated from coal fired plants, nuclear facilities, and other carbon and pollutant producing sources. This energy pollutes our environment when it is created. Costs real money. And therefore should not be thrown out into the environment. On a larger scale, projects like the Zollverein School and Hammarby Sjostad are have started to engage the idea that buildings can recover waste heat energy but the technology has not advanced far enough.

Who knows, maybe an adoption of ERV systems will cause a sea-change in the way people think about energy!

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

The Gilmakra House is the first of many new residences designed to meet the Nordic Svanen Miljomark certification of environmental and social sustainability. Features of these homes include super insulated envelopes, earth tubes to precondition outdoor air, solar electric / hot water panels, super efficient appliances, insulated glazing oriented to take advantage of solar radiation, and high outside air exchange rates for good indoor air quality. Modern architecture is also being used as a way to distinguish the homes from more traditional red painted Scandinavian homes nearby and also in the hope that urbanites from the larger coastal cities nearby will be attracted to this smaller city. It is important to note that because of its energy efficiency, the test house is being submitted for the German PassivHaus certification!

The Development

The development is actually part of a much larger regional development of southern Sweden which is occurring as a result of the new Oresund Link bridge from Sweden to Denmark. New housing and business opportunities are springing up all along the shoreline within driving or commuting distance of the connection. Energy House, the Danish development company, believes that there is a market in southern Sweden for modern environmentally friendly homes and plans to build 20+ houses beginning in the coming summer. One good sign is that over 2,000 visitors have toured the house during the winter both to see the modern architecture and study the sustainable features of the house. There is some debate in the mostly traditional (architecturally) town of whether or not to welcome the modern building into their city. That said, the overall reception is good.

Another sticking point is the cost of the house. 25,000 Kronor per square meter (roughly $380 SF) is a very high price for the area. Then again, it is of course one of Sweden’s first super efficiency houses. The developer builder, Johan Juncker, does however admit that the construction of this first super efficient sustainable house was in their words, “hellish, with many sleepless nights.” And goes on to say that, “next time it will be much easier (to build).”

The Design

The rectangular layout of the small house is very simple and modern. Half of the building appears to rest on a hillside and the remainder is held on steel columns. The one story structure is wrapped by a broad deck for outdoor living space and large window/door openings are provided to allow spaces to spill outside. The glazing is also placed mostly on the south and west sides to maximize the amount of solar heat gain in the wintertime. Interestingly, the house requires no additional heat (besides the sun) for 10 month of the year. The house is of course superinsulated with walls up to 50cm which are clad in durable wood shingles. The entire assembly is rated to last a minimum of 50 years! In the summer time an earth trench under the building stores coolth from a nightflush and uses it to cool the house during the daytime. The article does not mention anything about a energy recovery ventilator but I suspect that based on one note about high air change rates that the house is likely using 100% outside air for ventilation.

For more information please visit the original articles in Sydsvenskan and Helsingborgs Dagblad. Original post found at ByggExpo.

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

The Smith House, located in Urbana Illinois, is an all electric house built to the German Passive House Building Standard. To achieve the passive standard, architect and owner, Katrin Klingenberg, created a clean, efficient and comfortable house design using many of the passive house design strategies used in German model buildings. She describes the house as a “simple shed-roofed house insulated on all six sides to at least R-56.”

It is worth noting that Klingenberg ‘tweaked’ the Passive House standards to meet the unique climate conditions of Illinios, but that doing so did not compromise the strict energy efficiency criteria required to meet certification. The measured performance of the house is in fact below the level set by the Passive House standard. “The program specifications were written for Germany,” she notes. “But the climate here in Illinois is way more severe.” In designing Smith House to meet the Passive Standard in Illinois, the architect used several sophisticated computer models to refine the details of her thermal envelope including consideration for solar heat gain, internal heat gain, occupancy patterns, and energy loss through the skin of the structure. Klingenberg notes, “The surface/volume ration has to be very good… you do not want to have a lot of nooks sticking out of your house… because you lose energy.”

The Smith House design contains all the typical elements of single family home but with modifications to meet the Passive House Standard.

Envelope Design

The building foundation is uses a concrete slab poured over a 14″ thick layer of expanded polystyrene insulation (EPS). To keep heat from entering the slab at the edges, Klingenberg uses a 10″ thick concrete-block frost wall with 6″ of EPS on the exterior. Above grade this EPS block wall is shielded by a slate finish.

Exterior walls of the house are constructed using 12″ “Trus Joist” I-joists (TJIs) filled with blown fiberglass insulation. The wall cavity is sealed using OSB on both the interior and exterior sides. The exterior layer of OSB is covered completely in a 2″ layer of EPS secured with strapping back through the TJIs. A result of this thick wall is that it overhangs the foundation by 4″ and naturally provides a shield for the slate finish below.

To reduce infiltration into the interior, Klingenberg placed no electrical boxes in the exterior envelope. Instead the electrical boxes are all mounted on the the floor. In addition, light switches needed on the exterior are not hard wired. In leiu of hard wired systems, the architect found wireless light controllers that can be installed in shallow surface-mounted boxes. These two strategies were very important in maintaining the integrity of the air barrier.

The roof of the house is a “shallow-pitched single south facing plane framed with 16″ TJI rafters and insulated with blown in fiberglass.” Standing-seam galvanized roofing is installed as the exterior finish because of its thermal mass and reflective properties. There is a vent channel located between the roofing material and the insulation to allow built up heat in the summer to escape.

190 SF of fixed and operable triple-pane, argon, low-e windows allow natural daylight into the home. Most of the glazing is located on the south facade of the building both to admit daylight and solar heat in the winter months. In order to facilitate heat gain on the south facade glazing was chosen for its high Solar Heat Gain Coefficient (SHGC) of 0.51. That was varied on the west facade to SHGC 0.31 to reduce the impact of the hot western sun in summer months. Overall the glazing is rated to U-factor 0.17, which is roughly double the insulation of even the most efficient typically used glazing panels.

Systems Design

The Smith House uses a typical $450 instantaneous domestic hot water heater by German manufacturer, Stiebel Eltron. Klingenberg chose to use a low-cost low-tech tech system because of the relatively long payback and high maintenance attributes of Solar Domestic Hot Water systems.

Co-Creator of the Passive House Standard Dr. Feist agrees with this decision in principle by saying:

“We don’t calculate payback times—not on houses and not on solar thermal systems,” says Feist. “Instead we look at the annual energy cost and at interest costs. We can calculate the cost per kilowatt-hour saved from adding insulation, and compare that to the cost of including a solar thermal system. Solar thermal is by far the highest cost of any of the features we are discussing at the moment.”

The conditioning and ventilation system is designed to be simple and efficient. First, Smith House uses a Heat Recovery Ventilator (HRV or ERV) chosen because of the sophisticated climate controls available on the unit. The ERV uses the control / monitoring system to choose (using a damper) whether air comes preconditioned from an earth tube (8″ diameter x 100′ long) or, when outdoor temperature allows, directly from the outside. On very hot days air is also taken in using the earth tube to pre-cool the air. The house has no air conditioning (cooling). Heat is provided by an electric resistance heater located in the ERV unit. It is worth mentioning however that in most months the house requires little or no additional heating. “Last January the electric bill totaled only $35 despite the fact that the month included two weeks of -10° cloudy weather.

Cost

Building costs were higher than what could be expected for a comparably sized traditional home. Klingenberg notes that the construction is essentially a traditional ballon frame but that the build quality is higher. She estimates a 10% increase in cost to build such a home once contractors and designers become accustomed to the Passive House building standards. Klingenberg does note however that such a premium would be covered in about 10 years when calculating energy savings. The Smith House itself was built for roughly $110 per SF.

Smith House Project Details:

For more information read the original article or visit the Katrin Klingenberg / E-co Lab website.

For more information on Passive House design please visit Greenline’s previous post on the Passive House Building Standard.

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

(above) The original Passive Houses in Darmstadt

The Passive House (Passiv Haus) standard is an ultra-low energy building design system which uses extremely efficient building envelopes to significantly drive down energy consumption in structures. The standard is completely voluntary but does have a rigorous set of requirements that must be met in order to be classified as a Passive House. To date between 15,000 and 20,000 buildings of all varieties including houses, offices, schools, kindergartens, and supermarkets have been certified. Of the total number of buildings, the majority are however houses.

The Passive House standard was conceived during a series of conversations between staff at the University of Lund, Sweden, and the German Institute for Housing and the Environment. Their initial ideas were flushed out in research papers and then proof of concept housing models were built at the University of Darmstadt, Germany, in 1990. These first buildings were a group of four row homes that proved to be 90% more energy efficient than comparable housing using traditional building methods. The standard is now being supported by the EU sponsored CEPHEUS program and has been adapted for use in several other countries throughout Europe and even the United States. (The American examples include the Smith House and the Waldsee BioHaus)

To be certified a building must meet a strict set of standards. These include:

1. The building must not use more than 15 kWh/m² per year (4746 btu/ft²) in heating energy.
2. With the building de-pressurized to 50 Pa (N/m²) below atmospheric pressure by a blower door, the building must not leak more air than 0.6 times the house volume per hour.
3. Total primary energy consumption must not be more than 120 kWh/m² per year
4. The specific heat load for the heating source at design temperature is recommended, but not required, to be less than 10 W/m²

(The guidelines are flexible to a point depending on regional and climatic variation)

(above) The above thermal image shows heat loss from a Passive House (right) compared to a traditional house (left)

The comparisons between typical building codes and the Passive House standard are quite dramatic. For instance, in the United States, a house built to the Passive House standard results in a building that requires space heating energy of 1 BTU per ft² per heating degree day, compared to anywhere form 5 to 15 BTUs over the same period for a house built to meet the 2003 Model Energy Efficiency Code. This translates to between a 70 to 90% reduction in energy consumption for space heating and cooling. One Passive House home built in Waldsee Minnesota (at the Concordia Language Village) uses 85% less energy than a typical house its size.

Design and construction of these houses naturally follows a much more rigorous methodology than that used in traditional buildings (I would like to note however that as with most things, familiarity breeds efficiency and I would assume the same is true for new building methodologies). It is also worth mentioning that Passive Houses are documented to be no more costly than traditional houses of the same size. Designers are provided a “Passive House Planning Package” and use specially designed computer simulation software to predict the behavior of the building. Some of the design and construction strategies used in these houses are:

1. Passive Solar Design – leverage the sun’s energy by strategically lighting or shading the interior space
2. Superinsulation – high R-values for walls, floors and ceilings that are thermally broken whenever possible
3. Advanced Window Technology – usually employing triple glazed argon filled double low-e units with super insulated and thermally broken frames
4. Airtightness – minimize the amount of heat or coolth that escapes the envelope
5. Ventilation – including heat recovery ventilator systems and earth warming tubes
6. Space Heating – minimizes the size of heating components and maximizes internal heat gain from other heat sources in the building
7. Efficient lighting and electrical appliances

For more information on the Passive House standard please visit: The Passive House Institute, E-co Lab Passive House Projects, and Wikipedia.

The two US Passive Houses are posted on Greenline as Smith House: A Passive House in Illinois.

(This post was originally published on Greenlineblog by Ziger/Snead Architects)

Darmstadt wins #1 at the Solar Decathlon!

“Made in Germany” is the slogan of the Technische Universitat Darmstadt’s entry in the 2007 Solar Decathlon. It is hard not to stereotype Germans as orderly, precise, and thorough after you see their house. It is evident from just walking down Decathlete Way (the mainstreet for the Solar Decathlon on the Mall) that the Germans have taken the competition up a notch. I will leave it open though when it comes to winning the overall competition! The Decathlon is, afterall, about more than just architectural presentation, though good architecture is many times synonymous with all-round quality design.

The most striking aspect of the house is how un-solar it appears! There are no sloping PV panelized roofs. No hot water tube walls. No rain harvesting tanks. No futuristic material facades. It is just a simple modern cube of wood and glass. That is where the simplicity ends. In this regard, the house is a triumph in the integration of energy generation technology, computer simulation and modeling, and passive design.

Description (in their own words)

” For our house we focused on a passive energy concept. That means it is designed to demand a minimum amount of energy to be comfortable. For meeting the German “Passivhaus”-standard we developed a type of house especially made for the local clime. That means for Washington to design for a humid and hot subtropical atmosphere. The building is arranged in three layers.

The outer layer consists of oak louvered frames which, same as the roof, are equipped with photovoltaic. Thus they serve to generate electricity as well as providing protection from overheating, burglary and unwanted in sights. So the is an interesting relationship between inside and outside. In the south, between the outer and the second layer, the porch is situated. It serves as enlarged living space in the summer, and is protected and shaded by a roof of glass-embedded, translucent photovoltaic cells. The second layer is the thermal envelope, consisting of highly-efficient windows and walls. The third layer is the core in centre of living space. It is incorporating kitchen, bathroom and a major part of the building systems. Its walls are made of ACRYLITE. All devices are always serving several functions: The floor incorporates the lounge and the bed and building systems, the ceiling includes lighting systems and radiate cooling, the walls, beside storage spaces and integrated consumer electronics, furthermore contain thermal mass through phase changing material, a new material which can store energy like a massive stone wall. The light-weight wooden post-and-beam structure combined with the core ensures stability. To allow recycling and reconfiguration we avoided insolvable connections and favored renewable or local materials as much as possible. The flexible interior space meets the demands of multiple users’ requirement. Therefore the floor integrated lounge and bed can be opened and closed, the bathroom is expandable. Everything can but doesn’t have to be changed. The occupant has almost unlimited freedom to adjust the house to his way of life.”

PV Louvers

All sides of the house are faced with operable louvers. What makes these louvers unique is that each oak louver has a small solar panel placed on it. The louvers are geared so that they operate in unison and can be closed off to give privacy or opened to allow light into the house. I did not see any automated control systems on the louvers and I suspect the intention is not to have them track the sun, rather they sacrifice a percentage of efficiency so that the louvers can function as a privacy screen. Amazing is the way the PV panels are installed. Each louver must be connected to the house power system. The photos below show carefully these elements were detailed. Beautiful!

Perforated PV Ingots

The Darmstadters also impressed me with the first application I have ever seen of perforated crystaline PV ingots. The team contracted with a German company to die-cut the crystaline PV ingots so that they let light through. For those of you unfamiliar with crystaline ingots, it is usually opaque because of its thickness. Amorphous silicone can be translucent but is less efficient. The result is a functional and beautiful space. See the photos below.

Phase Change Materials (PCM)

The house also uses phase-changing microcapsules of paraffin in the ceiling and walls on the east and west sides where the envelope is opaque. The microcapsules change state from solid to liquid as they are heated by the sun during the day, then slowly release this heat back into the house during the night. The paraffin is a lightweight alternative to such things as trombe walls which use water or concrete for thermal mass. Paraffin is low cost, non toxic, hydrophobic and has a phase change range which makes it suitable for application in houses. PCM materials do not contribute directly to the energy efficiency of a home, but by reducing the high diurnal temperature swings inside a home they keep equipment from running at peak and therefore save energy.

Overall the house is a wonderful example of how energy efficiency, energy generation, and good design can all work together to create spaces for living. I hope more sustainable projects take cue from this project.

For more information please visit the Darmstadt Solar Decathlon website.

(This post was originally published on Greenlineblog by Ziger/Snead Architects)