The technology that makes LISI an eco-friendly model-building is almost invisible. Many visitors do not even notice the tiny engineering room, all the photovoltaics is hidden on the roof, and only a few slits in the floor show that there is a ventilation system. Nevertheless, the technological aspect of the project plays a crucial role. From the very beginning, architecture and engineering had to work hand in hand, otherwise developing an aethetically pleasing plus-energy-house would not have been possible.

There is a lot LISI has to offer when it comes to technology: „Our ventilation system in the floor, which can both heat and cool the room, is definitely remarkable“, says Sabrina Novalin. She studied at TU Vienna, is now working for AIT, and she was one of the masterminds behind the technological concept of LISI. Cold water can be pumped into the pipes in the floor. Air flows past these pipes, cools down and is pumped into the room. In addition to that, the drawing-off air from the warm water heat pump is used to cool the room: The pump produces hot water and cold, dehumidified air, which can be pumped into the house.

The bathroom has a very special feature as well: „Usually, warm water from the shower just goes down the drain – but we wanted to harness its energy“, says Sabrina Novalin. The warm waste water goes into a heat exchanging device, directly in the shower tray: The arriving cold water is pre-heated by the waste water so that less hot water has to be added to arrive at the desired temperature. Also, the building’s warm water tank is pre-heated with waste water from the shower.

There is not only a heat exchanging system for water, but also for air: On cold days, the warm outgoing air heats up the incoming cold air from outside. The heating system just hast to further increase the temperature of the pre-heated air, it does not have to deal with ice cold winter air. The heat exchange system also regulates the humidity: Special materials, which can absorb and release humidity, are used to regulate the indoor climate.

No new technological components had to be developed for LISI. „If we had done that, it would have made the house much more expensive. Apart from that, it does not make sense to give the customers experimental prototypes, which cannot even be properly installed by their local plumber“, says Sabrina Novalin. The big challenge was to assemble the right components and create a complete system in which all the parts work together. It would be easy just to install and show off some fancy piece of equipment – but this has nothing to do with sustainability. Only when all the components complement each other perfectly, the house can be eco-friendly and pleasant to live in.

We know from the public tours at the Solar Decathlon that quite different people from various age groups are equally enthusiastic about LISI. But of course there is a specific audience which is targeted by this building concept. After all, marketability is one of the ten criteria of the competition.

LISI is not a large family home, it is designed for two people – for young, modern couples who put a lot of emphasis on a green lifestyle, or older couples whose kids have moved out.

In Vienna, an interesting development can be observed today, which could have a great influence on LISI’s maketability: Community gardens are turned into residential areas. In the 1920s and 1930s, large areas were made available for individual gardening. These areas were not meant to be inhabited, the idea was to give the urban population a chance to grow vegetables and produce food.

Today, there is no fear of food shortages any more, but the demand of urban living space is increasing. Therefore, many community gardens are rededicated. It is now allowed to live there permanently, but there are size restrictions on the houses which are built in these areas. This way, a demand for small, detached houses for an urban target audience is created – that is where LISI could do very well.

Another great opportunity for a house like LISI is tourism: There is an increasing number of hotels, which do not only provide their guests with a room, but with a suite in a separate building. An ensemble of LISI houses could be a futuristic and energy efficient way of building hotels.

Where is the dividing line between indoors and outdoors? When you are looking at LISI, Team Austria’s building at the Solar Decathlon, this is very hard to say. The main architectural idea of the building is the seamless connction between the spacious living room and the patios in the north and south of the building. When the weather is nice, the glass front on either side can vanish into the wall and a partly roofed living space is created, which is about twice as large as the interior alone.

The floor plan is quite simple: LISI was designed in such a way that the open area for living, cooking and dining is as large as possible. Bathroom, bedroom and the engineering room on the other hand are rather small.

LISI is almost entirely made of wood. Therefore it is fitting that also the architectural concept is inspired by trees: Much like the trunk of a tree, which transports water and provides structural stability, the module consisting of the bathroom, the bedroom and the engineering room forms the core of the house and is rooted in the wooden groundwork.

The structural elements of the exterior wall define the visible form of the house, similar to the large branches of a tree. Instead of leaves, LISI has white wavy curtains made of a robust, weather-proof material. They can be drawn to create a private space, or they can be pushed aside to open the house up.

LISI, Team Austria’s house, was designed to look elegant, simple and inviting. To the untrained eye, it may not look like a high-tech building. „What matters in architecture is the people“, says Karin Stieldorf, the Austrian team leader. „Of course, technology is important too, it has to work perfectly, but we do not show it off.“

The visitors’ attention is not directed to technological devices, cables and sensors, but to simple wooden surfaces. While other teams at the Solar Decathlon use a considerable portion of the building’s space for building equipment and appliances, the size of the engineering room in the Austrian house is quite modest. Most of the other houses have photovoltaics which is clearly visible from the street, LISI’s photovoltaics can only be seen from above. „Using photovoltaics used to be a statement, something to show off. Today, it should be something completely normal, we do not need to display it any more“, says Karin Stieldorf.

Eco-friendly architecture does not need to have „eco“ written all over it – that is what team Austria wants to show. The fact that LISI is a great example of sustainable architecture will be proven by tests and measurements, there is no need for constantly visible reminders. Therefore, the architecture of LISI is more about understatement and simplicity. The visitors at Solar Decathlon seem to enjoy that, we can only hope that the jury likes it too.