Sustainability Report

Sustainability information provided by Allen + Crippa. 

Internal principles and design logic

• For projects such as Gässli5, we do not consider certification systems to be the primary drivers of sustainability. More decisive is a fundamental cultural shift among architects, clients, contractors, and society at large. Sustainability, in our understanding, emerges from a coherent set of values and decisions rather than from compliance with labels.
• In Gässli5, all stakeholders shared a genuine commitment to a resource-conscious approach. This collective mindset formed the conceptual framework of the project and guided decisions throughout the process.
• Certification schemes often address only partial aspects of sustainability and can encourage technically driven optimisation without questioning broader resource implications. Our approach instead relied on internal principles such as sufficiency, circularity, and material-appropriate construction.
• The project was guided less by quantitative benchmarks than by critical questions: What can be preserved? What truly requires new construction? How can materials remain within circular flows?

Embodied carbon strategies

• The historic structure was carefully dismantled following a complete documentation process. Missing elements were sourced from other demolished houses within the village. In this way, not only materials but also local construction knowledge were carried forward. Bricks, beams, and secondary structural members were supplemented from regional demolition sites, creating a form of reuse involving components up to 350 years old. Newly added timber originates from the forest above the village. The spaces between the beams were insulated with sheep’s wool.
• The new building was conceived as a monolithic rammed earth structure, entirely free of cement. Its construction follows the principle of mono-material assemblies. The rammed earth walls and floors were realised in collaboration with Lehm Ton Erde, a Vorarlberg-based specialist in earth construction, using locally sourced soil that was prefabricated under controlled conditions to ensure precision and construction efficiency. 
• Hemp-based insulation materials were supplied by Hanfhandwerk, a Swiss manufacturer specialising in hemp construction materials. 
• The lime plaster incorporating recycled brick dust was developed as a custom mixture by Gebrüder Beck, a regional lime producer.
• Stone elements on the facade were executed in Swiss natural stone, specifically Mägenwil shell limestone. All stone components were dry-laid rather than glued. 
• Nearly all materials were evaluated in terms of life cycle impact, recyclability, disassembly potential, and harmful substances. This approach extended to the interior fit-out. The rammed earth floor is sealed with natural carnauba wax. The ceiling build-up includes a loose fill mixture of cork, clay, and wine-industry by-products. Interior plasters were produced using recycled brick dust sourced directly from the construction site.
• Even the furniture was assembled using wood joinery and a natural fish-bone glue commonly found in instrument making, with no toxins. All timber surfaces remain untreated, including floors, windows, and kitchen worktops.

Embodied carbon overview

• A comprehensive embodied carbon assessment has not yet been completed, although we intend to carry this out in the near future. It can be assumed that the embodied energy is lower than that of a comparable new building. The greatest leverage lay in the preservation and reuse of the existing structure. This was reinforced by the deliberate avoidance of CO2-intensive and cement-based materials and the prioritisation of bio-based materials such as clay, timber, and lime.
• The ambition was to construct a building that generates almost no waste, minimises CO2 emissions, and relies exclusively on natural raw materials. The new building is designed so that, at the end of its life cycle, its materials can be reintegrated into biological or technical cycles with minimal loss.

Operational emissions strategies

• Operational energy was not optimised through technical systems, but through passive strategies, thermal mass, and seasonal patterns of use. Gässli5 is therefore not a high-tech efficiency project, but rather a low-tech sufficiency project.
• Operational energy performance was studied, particularly in relation to whether additional insulation could be omitted. The calculations indicated that annual heating demand would remain nearly comparable, as portions of the exterior walls could be activated as additional thermal mass. The thermal inertia of rammed earth plays a decisive role in this regard. However, due to current building regulations, the house ultimately had to be insulated despite these findings.
• In the historic building, insulation layers, building services, and composite materials were deliberately avoided. This ensures that the house remains repairable and fully reversible in the future.