Green Solutions Awards 2020/21

Das Eisbärhaus ist in zwei Bauteile gegliedert, die über einen offenen, kalten Erschließungskern miteinander verbunden sind. Als Wind- und Wetterschutz dient ein engmaschiges Edelstahlnetz. Das Gebäude präsentiert nach außen seinen ökologischen und energetischen Charakter. Der Vorarlberger Ökoleitfaden diente als Grundlage für die Auswahl der eingesetzten Baustoffe. Jedes Produkt wurde hinsichtlich dessen „Grauen Energie“, der benötigten Energie bei der Herstellung des Produktes, geprüft. Ein weiteres Kriterium stellte die möglichst geringe Belastung von Mensch und Umwelt sowohl im eingebauten Zustand als auch bei der Herstellung und der Verarbeitung dar. So stammt das ausgesuchte Holz durchweg aus Baden-Württemberg. Die Außenwände des Eisbärhauses sind aus geschosshohen, vorgefertigten Wandelementen erstellt. Diese sind über eingelegte Halfenschienen am Stahlbetonskelett befestigt. Die Wandelemente bestehen aus einer mit Zellulose ausgeflockten Holzkonstruktion aus Wärmedämmträgern. Der gesamte Baukörper ist mit einer Holzschalung (Weißtanne aus dem Schwarzwald) versehen.

In den Gewerbeeinheiten dienen die Betondecken, die über im Rohbau eingelegte Rohre aktiviert werden, als Heiz- bzw. Kühlflächen. Die Wohnungen verfügen über Fußbodenheizungen. Das Erdreich wird als Wärme- bzw. Kühlquelle genutzt. Eine reversible Sole-Wasser-Wärmepumpe ermöglicht die Beheizung und Kühlung des Gebäudes. Die Lüftungsanlage ist vom Heizsystem entkoppelt. Die über das Dach angesaugte Frischluft wird in 3 Schritten auf Raumtemperatur gebracht und in die Räume eingeblasen. Das Dach des Eisbärhauses wurde mit einer Photovoltaikanlage gedeckt. Ziel ist es, energieautark zu werden.

Sowohl das Gebäude als auch der Innenausbau ist in dem im Holzbau gängigen Achsraster von 62,5cm angelegt. Das Büro ist nach dem Prinzip eines Kombibüros aufgebaut. Der massive, aussteifende Kern in der Mitte des Grundrisses beinhaltet alle Nasszellen sowie Technikbereiche. Alle vertikalen Flächen im Inneren haben eine Oberfläche aus Weißtanne (sägerauh). Die horizontalen Flächen wie Ablagen und auch der Boden, sowie deutlich mehr beanspruchte Flächen wie Griffleisten, sind in Eiche ausgeführt. Die Arbeitsplätze sind an den Fassaden angeordnet. Verschiebbare Holz und Glastafeln bieten die Möglichkeit, einzelne Bereiche flexibel abzutrennen.

In the centre of Kirchheim unter Teck (Germany), a building that sets new standards was completed with the extension of the Eisbärhaus (means: Polar Bear House). The project optimises sustainable building in many areas. and therefor, the German Sustainable Building Council (DGNB) awarded the climate-positive residential and commercial building a platinum certificate. With the highest rating ever achieved by a new building in the DGNB certification process, the Eisbärhaus currently ranks as the most sustainable building in the world.

The property "Hindenburgstraße 34" was acquired in 2018 in order to expand the residential and commercial building "Eisbärhaus", which was built in 2009, as new building. Like the Eisbärhaus (components A+B), its extension (component C) was also designed as a passive house.

In addition to two flats, the building also houses a day care centre for children, which BANKWITZ beraten planen bauen GmbH operates together with the Tageselternverein Kreis Esslingen e.V.. In addition, two commercial units can be found in the new building. A special feature here is the glass walkway on the first floor, which connects the offices of BANKWITZ GmbH in the existing Eisbärhaus with the additional space in the new building.

Certified and climate-positive architecture

The DGNB certification system is based on the three pillars of sustainability: ecology, economy and socioculture. With 94.2 per cent, the highest result ever achieved, the extension of the Eisbärhaus (Component C) was officially awarded the platinum certificate during the World Green Building Week 2020. In addition to the platinum award, the Eisbärhaus was one of the first buildings in Germany to receive the "climate positive" award, which confirms CO2 neutrality in operation. According to the DGNB definition, the new Building C is also already climate-positive: after three years in operation, the CO2 savings will now continue to cover the operation and, in addition, the entire production costs of the building.

This is made possible by the implementation of a holistic building concept:

Ventilation concept

Each utilisation unit is ventilated by a decentralised comfort ventilation unit, which ensures hygienic air exchange and allows for free ventilation. In Building C, the amount of air supplied is controlled by a CO2 sensor. This sensor continuously measures the air quality in the room and then supplies the appropriate amount of fresh air.

A heat exchanger extracts the heat from the exhaust air in winter and passes it on to the fresh air drawn in (heat recovery efficiency approx. 85%). Thanks to this heat recovery, the building has very good thermal comfort and pleasant indoor climate conditions. Since the air is blown in at room temperature due to the pre-heating, there are no draughts. In addition, the fresh air is fed through a pollen filter, which is particularly advantageous for allergy sufferers, as it prevents pollen from entering the interior.

The exhaust air is released into the environment via the underground garage. This means that the residual heat in the exhaust air can be used to heat the underground car park. The internal heating loads of the polar bear house, such as people or technical equipment, are thus fully utilised.

Heating/cooling the building

All units in Building C are additionally heated by means of a building component activation system. The heat required for this is drawn from components A+B, as there is usually a surplus of energy there due to the internal heat loads (local heating network). In the existing polar bear building, the rooms are heated via geothermal energy and a brine-water heat pump. The cooling supply for Building C is provided by four geothermal boreholes.

Already during the planning phase, alternative floor plans were developed for Building C in order to be able to meet future changes in user requirements without interfering with the building services. Due to the central shaft routing and the arrangement of the heating/cooling supply in the walls and ceilings, any conversion measures can be carried out without (or with only minor) adjustments to the building services.

Further ecological measures

A photovoltaic system with a nominal output of 25.92 kWp was installed on the roof of Building C. The electricity produced is mostly used in the building itself. Most of the electricity produced is consumed in the building itself. Before feeding electricity into the public grid, the existing e-bikes and electric vehicles are first charged. In addition, the self-produced electricity can also be consumed at a later time by using a battery storage system (40.96 kW). The Eisbärhaus achieves an electricity self-sufficiency rate of about 40%.

Solar collectors are used in the Eisbärhaus to heat the domestic water. The hot water supply in Building C is also provided by the existing building. The water for flushing toilets and watering the garden is taken from cisterns (components A+B = 29,300 litres capacity; component C = 12,000 litres capacity). These collect all the water hitting the sealed surfaces. All open spaces remain unsealed and thus as infiltration areas.

The heat, sun and glare protection is controlled via a central weather station. The exterior screens are automatically raised or lowered depending on the position of the sun and the strength of the light and wind.

The entire building technology is controlled with the help of a measurement and control system. All consumption figures are recorded and continuously monitored via the central data acquisition system. Malfunctions or optimisation options can thus be detected and corrected at an early stage.

Selection and recyclability of building materials

It is not only from an energy perspective that the Eisbärhaus and its extension set standards. The choice of building materials is also exemplary.

Building C was constructed as a reinforced concrete-wood hybrid building. The Vorarlberg eco-guideline and DGNB quality level 4 served as the basis for the selection of the building materials used. Each product was tested with regard to its "grey energy", the energy required in the production of the product. Another criterion was that the products used should have as little impact as possible on people and the environment. And this not only in the installed state, but also during production and processing. Regional products and materials with sustainability labels always had priority. Wood as a naturally renewable raw material fulfils all these conditions and creates a healthy feel-good climate in the interior due to its warm and lively effect.

A total of around 100 cubic metres of wood were used in the project. This is roughly equivalent to ten spruce trees with a height of 40 metres. The wood takes two and a half days to regrow on the 1,000 hectare forest area in the town of Kirchheim unter Teck.

Recycled concrete (RC concrete) was used for all concrete work, including the water-impermeable concrete (WU concrete). In addition, a floor slab in recycled concrete was also constructed for the first time in Building C as a pilot project.

Prefabricated façade

In order to increase the degree of prefabrication and to shorten the assembly time on site, all exterior walls were prefabricated in the factory. This meant that the building could be erected within just a few days. The different depths of the silver fir profiles create exciting plays of light and shadow on the façades (depending on the time of day and the weather). The exterior walls consist of wooden elements with cellulose insulation and untreated, rough-sawn wood cladding. The window sashes and frames are also untreated.

Due to the elemental exterior walls and the reinforced concrete skeleton, the façade can be deconstructed and recycled without interfering with the supporting structure.