Sustainability Report

Timber construction and reduced structural load

A key environmental strategy lies in the use of lightweight engineered Austrian timber for the rooftop construction. This choice reduces structural load on the existing building, a critical consideration in vertical extensions, while lowering embodied impact in comparison with more conventional concrete construction. 

In adaptive reuse projects of this kind, material weight and buildability are inseparable from environmental performance, and the use of engineered timber allows the addition to remain technically feasible and materially efficient.

High-performance envelope and energy compliance

PR33 was designed to perform within the constraints of an inherited early twentieth-century building while complying with Germany’s tightened EnEV 2014 standards at post-2016 level. Its primary energy demand is 74.27 kWh/m²a, equivalent to 85 per cent of the reference building requirement, while transmission heat losses are reduced to 48.6 per cent of the allowable maximum. The project achieved Energy Efficiency Class B, indicating a strong level of thermal and operational performance within the context of rooftop residential construction.

This performance is supported by an optimised envelope. The addition uses high-performance insulation rated WLG 032 / 035, detailed to reduce thermal bridging and improve continuity across the building fabric. Triple-glazed systems by Velux for roof windows and Schüco for façade glazing provide a U-value of 1.10 W/m²K, while external shading measures ensure compliance with German summer heat protection requirements. Together, these strategies support lower operational demand, improved indoor comfort, and consistent year-round performance.

The building incorporates high-efficiency heating systems that combine condensing technology, solar-supported domestic hot water, and the later integration of heat pump solutions. This layered energy strategy reduces primary energy demand while aligning the project with Germany’s renewable energy requirements and contemporary expectations for residential performance.