Atrium as Green Oasis
The building is accessed by means of a wide passageway leading into an open-air atriumâthe green oasis at the heart of the building. Spaces for public use on the ground floor, such as a restaurant, a gym, and rentable event and meeting spaces, all open onto an arcade that leads to a ring of office spaces on the upper floors, totaling approximately 10,000 square meters. The atrium, an outdoor recreational space for employees, houses a biotope irrigated by collected rainwater which also serves as a habitat for a variety of plants and animals; climbing vines growing along the courtyard facades filter CO2 and other pollutants, contributing to a comfortable and healthy atmosphere.
Flexible Use
The design focuses on the premise that the innovative and productive exchange of ideas is an important prerequisite for productivity. Open layouts offer flexibility and accommodate diverse uses; open lounges on each floor allow different users to meet without the need for formal collaborations. The publicly accessible ground floor features a long terrace for outdoor gathering which extends southwards and visually links to a park in front of the building.
Materials in Circulation
HORTUS stands for House of Research, Technology, Utopia, and Sustainability, and is focused on innovative and ambitious sustainability concepts. Hence, the design process began with an extensive scientific material analysis, in which construction materials were tested and compared for their environmental and physical characteristics. A key criterion is that the materials should originate from natural and renewable resources as much as possible. Along the lines of a âcradle-to-cradleâ principle, all building components employed are to be catalogued and made available for reuseâif not able to be reused, they must be biodegradable. A reduced palette of renewable materials such as wood, compressed clay, and cellulose, along with glass for windows and solar panels, underscores the ecological tenets of HORTUSâs modular timber-frame construction. Timber joinery is employed to avoid metal connections, so that at the end of the buildingâs life span, the components are easily dismantled and reused. Spaces are ventilated naturally, and the compressed clay inserts on the ceilings and parapets ensure a comfortable and healthy interior climateâcompressed clay regulates humidity and absorbs excess heat, which is released through the windows at night during the warmer months.
New Floor System
In collaboration with ZPF engineers, the Herzog & de Meuron team developed a hybrid floor system of rectangular timber elements and compressed clay. The ceiling modules were perfected with the additional, further collaboration of Blumer Lehmann and Lehm Ton Erde. Each individual hybrid element consists of a prefabricated wooden frame, using timber harvested from various forests in the immediate vicinity. Clay is compressed between the frameâs inlaid wooden beams in the form of a vault. The dense clay acts as fire protection and at the same time ensures a comfortable indoor climate.
The production of the hybrid clay-timber floor slabs is conducted locally: clay is extracted from excavated earth from the construction site, while each clay-wood floor slab is manufactured in the field factory on the neighboring property. Using a process specially developed for HORTUS by Lehm Ton Erde, the clay mixture is produced directly on site and tamped into the wooden modules. The production of the clay-timber floor system results in ten times less CO2 emissions than a conventional flat concrete floor.
Clean Energy and Minimization of the CO2 Footprint
The design targets a drastic minimization of the buildingâs CO2 footprint and aspires to a holistic sustainability concept. By doing so, it substantially exceeds guidelines for environmentally sustainable building, such as SIA 2040. The compact form reduces energy loss and, without a concrete basement, excavation remains minimalâthe building essentially floats over the landscape. The air underneath the building is cool in summer and warm in winter. This advantage, together with geothermal energy for heating and cooling, is used to regulate the buildingâs temperature. A photovoltaic surface of approximately five-thousand square meters on the roof and along the parapets enables the independent provision of renewable, resource-conserving solar energy; this system simultaneously generates such a surplus that the embodied energy necessary for constructing the building is offset within thirty-one years. HORTUS thus becomes a fully energy-positive building after one generation.
Sustainability at HdM
Herzog & de Meuron understands sustainability as an important benchmark of quality and a fundamental value of our office. Sustainability should be a feature not only of our built environment but also of how we live within it, with a focus on a holistic approachâaway from generic statements and towards action. In the development and realization of projects, the goal is to create a balance of environmental, economic, and socio-cultural conditions that allow buildings to address todayâs issues in meaningful ways.
The construction sectorâaccording to studies by the IEA (International Energy Agency) and the WEF (World Economic Forum)âis responsible for the consumption of approximately 40 percent of all raw materials and energy and is simultaneously one of the main producers of CO2 emissions worldwide. As architects, we see it as our task to influence this statistic. The question of how to plan a climate-neutral building is an architectural challenge that not only requires environmentally sound building principles, but also the adoption of an incisive, ongoing process, which entails finding the best possible approach for each individual situation. This requires a high level of innovation and solution-oriented design, custom-tailored for each geographic, urban, and cultural context.
The example of HORTUS demonstrates that future-oriented architecture can act as a local source of energy and raw materials, while simultaneously being aesthetic, healthy to build and occupy, and useful for the economy, the environment, and our society.
