Architecture and Identity
In the future, the expanded vocational school in Bülach will be perceived as an ensemble of distinct buildings. Visually, the buildings are connected through their façades, which—despite differing in materials—relate to one another through vertical reliefs, horizontal ribbon windows, and striking sawtooth roofs. Functionally, each part of the ensemble has a separate entrance with generously sized forecourts to manage traffic flow and enhance safety. Internally, however, both buildings are directly connected at ground level, ensuring circulation and enabling spatial or functional synergies. 

Aesthetics of Reuse
The design of the new building expresses its dismantlable concept. Space is defined through the addition of individual components—from shell to fit-out—and through the distinct separation of materials. This creates an aesthetic and atmosphere that is immediate, straightforward, and easy to understand. The structural frame, or primary system, provides the basis and organizational logic for the interior fit-out, which can be adapted to functional and spatial requirements. Where possible, façade panels from the deconstructed pavilions may be reused as interior wall cladding. All newly used materials are durable, certified, recyclable, and, where possible, of natural origin.

Thermal Comfort and Wellbeing
To avoid overheating in summer, classrooms are oriented northwest and southeast. Roof overhangs fitted with photovoltaic panels and a continuous parapet provide additional shading and largely glare-free workspaces. The interior corridor that runs crosswise through the floor plan also supports cross-ventilation.

Cost Efficiency
Cost efficiency in both construction and operation is driven by a strategy of sustainable planning. The compact design saves space and results in an optimized and energy-efficient ratio of volume to envelope. The near-complete avoidance of a basement reduces both construction costs and the use of CO₂-intensive concrete. A prefabricated structural system, designed for a strict load path, enables resource-efficient disassembly and future reuse. In operation, modular prefabrication combined with separated systems facilitates cost-effective changes in use and resource-friendly structural adaptations.

Structural System
The structural design is based on systems commonly found in industrial construction. In the interest of sustainability, the most efficient material is used for each structural component depending on its location. Structural bracing for seismic safety and wind loads is provided through cross-shaped shear walls at the façade, emphasizing the industrial character of the structure.

Designing for Disassembly
The core concept of the structural system is its complete disassemblability, enabled through consistent separation of components. All joints are designed as demountable bolted connections. In addition to this fundamental reversibility, the grid and dimensions of all components are standardized, making the system suitable for future buildings with different uses. In line with circular construction principles, this ensures that all structural elements can be reused wholly or in part at the end of the building's life cycle.

Sustainable Foundation Design
Since the building is constructed without a basement, the foundations rest on weak, settlement-prone hillside deposits. Traditional methods using lean concrete or deep pile systems are avoided due to their high CO₂ emissions and impact on groundwater flow. To transfer building loads to compact moraine layers and address potential settlement issues, cement-free soil improvement techniques with favorable environmental profiles—such as bio-consolidation or vibro stone columns—are used. The system is optimized in collaboration with a geologist.

Building Systems
Building systems are increasingly important, especially regarding energy demand and embodied energy. At the same time, modern buildings are expected to offer maximum comfort and wellbeing—standards now taken for granted. This project demonstrates how conscious decisions can reconcile high comfort with sustainable solutions. Energy standards such as Minergie or SNBS are naturally met, but the focus is on interdisciplinary collaboration between architecture, building systems, and usage, going far beyond off-the-shelf solutions.

Integrated Heating and Cooling
The new building is designed for optimal integration with a potential energy center, e.g., using reversible heat pumps and geothermal probes. An internal substation ensures efficient energy distribution. Underfloor heating with integrated sensors and valves enables both heating and cooling without additional investment in cooling systems. The system is compatible with alternative heat sources such as woodchip heating.

Innovative Ventilation Concept
A minimalist ventilation strategy ensures maximum efficiency with minimal technical complexity. The wide corridor between classrooms acts as the building's "lung." Depending on external temperatures, this area is ventilated via mechanically operated windows. Classrooms individually draw fresh air from the corridor, regulated by CO₂ sensors to ensure optimal air quality.

Photovoltaics and Façade Integration
Photovoltaic systems on the roof and façades cover 94% of the building's annual electricity demand directly on site. In summer, the PV system can supply 100% of the electricity for both the new and existing buildings, with surplus power fed into the grid.

The façade elements also provide shading, reducing summer heat gain—ideal when combined with underfloor cooling. In winter, low sun angles allow sunlight to enter the rooms, supporting passive solar heating.

Rainwater Use
Rainwater is collected in a tank and used for irrigating the outdoor areas. This saves water and contributes further to resource conservation.

Sustainability Through Interdisciplinary Planning
The interdisciplinary planning of building systems, structure, and architecture results in a building that balances sustainability, aesthetics, and low-tech solutions. The goal is to meet energy and sustainability standards through architectural and structural means—not purely through technical systems. Orientation to the sun and adequate shading ensure minimal heat gain in summer. The compact form, simplicity of the structural system, and principles of component separation and disassembly support the needs of a school, allowing future adjustments or renovations with minimal effort and low energy and material use.

Validation with the provided calculation tool confirms a GHG value of 8.8 kg CO₂/m² GFA/year. A refined calculation with the Eco-Tool corrects this to 6.0 kg CO₂/m² GFA/year for construction and 0.6 kg CO₂/m² GFA/year for operation.