Collegium Academicum IBA | DGJ Architecture | Media - Sustainability

Custom Certificates

NaWoh

Sustainable Housing

2024

Low Carbon

Embodied carbon overview

Collegium Academicum is based on ‘Open Architecture’, a prefabricated timber system developed by Hans Drexler, founder of DGJ Architektur. The primary structure uses solid and glue-laminated timber and is assembled with form- and force-fit carpentry joints, without metal connectors. The timber construction was carried out by ZÜBLIN Timber.
Beyond the visible timber construction, key carbon-related decisions included the use of timber as a carbon store, a recycled concrete foundation slab, recycled on-site fill, and prefabrication to reduce waste and on-site construction time. The courtyard facade, which also serves as the escape route and had to be non-combustible, is an aluminium-sheet facade made from 90 percent recycled raw material.
The project is certified under NaWoh, the German Quality Label for Sustainable Housing, which includes the life-cycle assessment. The whole-life global warming potential over 50 years is 20.2 kg CO2-eq/m² net room area/year, based on NaWoh/eLCA and Ökobaudat data. The manufacturing phase is near-zero owing to the timber structure’s biogenic carbon storage, meaning the operational phase dominates the balance.
Ecological target specifications were written into the tender and verified by accompanying research. Collegium Academicum is part of IBA Heidelberg and was developed within publicly funded research frameworks, including BBSR ZukunftBau Variowohnungen and Holz Innovativ/EFRE.

Low Carbon

Operational emissions overview

Sufficiency guided the project’s approach to living space, with a per-capita living area of about 23 square metres, roughly 20 square metres below the German average. This reduces both embodied and operational footprints.
The building meets KfW/BEG Efficiency House 40 Plus and Passive House principles. Energy performance certificates, EnEV/GEG, exist for all building bodies. Indoor-air quality was also tested against the AgBB scheme after completion.
In operation, the residential buildings achieve final-energy class A, with final energy of approximately 37–39 kWh/m²·a, primary-energy demand of about 12–14 kWh/m²·a, and CO2 emissions of around 11.5 kg/m²·a.
A rooftop photovoltaic array of 180.4 kWp, combined with a 138.6 kWh battery, covers at least 100 percent of residents’ electricity demand on an annual balance.
Heat is supplied by district heating, with EEWärmeG coverage of 94.1 percent for the residential buildings, complemented by mechanical ventilation with heat recovery.

Adaptive Reuse and Flexible Design Considerations

Adaptability is central to the design. Internal walls sit on a structural grid and can be built and moved by residents themselves — within hours and while the building is occupied — using the in-house workshop. Each individual room is divided into a 7-square-metre fixed core and a 7-square-metre flexible zone.
Four-person flats can be combined into larger shared flats or adapted for assisted living. Bathrooms are pre-reinforced for later barrier-free use, allowing the building to remain useful across its life cycle.

Disassemblable Elements for Circular Economy

The project’s material strategy is based on generic, widely available, and cleanly separable material categories rather than proprietary technical systems. For glazing, insulation, building services, and interior fit-out, the project description deliberately remains at material level rather than naming specific proprietary products. This reflects the project’s ‘as simple as possible’ approach, with the sustainability rationale lying in recycled content, recyclability, and separability.
The timber primary structure was designed for disassembly and reuse. Its form- and force-fit carpentry joints allow components to be separated cleanly and reused, while the aluminium-sheet courtyard facade can also be separated into its individual material components.