HORTUS Fact #2 – Radical Sustainability

From Vision to Mission

The vision was to create a building that would pay back its embodied non-renewable energy within a single generation and become energy-positive after 30 years. To achieve this radical sustainability goal and turn utopia into reality, interdisciplinary teams from SENN, Herzog & de Meuron, ZPF Ingenieure, Blumer Lehmann and the clay specialists at Lehm Ton Erde worked intensively together. Developing the innovative ceiling, made from timber and rammed earth, took around seven months before it met the ambitious requirements, including strict fire safety regulations.

Go local

As a CO₂-intensive building material responsible for around 10% of global greenhouse gas emissions, concrete was omitted from HORTUS wherever possible. The only exception are the short piles driven into the groundm on which the building stands. Unlike a full basement, their carbon footprint is negligible. Instead of concrete, local materials such as timber, rammed earth, and recycled paper were used. The ceiling elements of HORTUS account for only about 7.5% of the building’s total CO₂ emissions. In comparison, a conventional reinforced concrete flat slab would contribute roughly three times as much (around 25% of total emissions).