FACING THE FUTURE OF FACADES: To Become a Model

Renovating existing buildings is a significant global challenge, often complicated by the lack of temporary replacement properties. However, this example demonstrates that with clever and innovative solutions, buildings can not only be refurbished to become more future-ready but can also be expanded while remaining operational.

The urgency is palpable: Climate change demands immediate action. By 2050, annual greenhouse gas emissions must be reduced by 80 to 95 percent compared to 1990 levels. This necessitates prioritizing ecological and economic principles in energy-efficient refurbishments, leveraging existing building materials, preserving values, and reducing energy consumption rather than constructing new buildings. This approach was successfully implemented at the Niederwalgern Comprehensive School in Germany by Rubner Holzbau GmbH.

There is still much to be done, but a great deal can already be accomplished. For example, building as much as possible with wood. The more, the better, as this is considered active climate protection and a significant contribution to climate protection goals. The greatest CO2 binding, and thus substantial savings potential, occurs in the construction industry: Every cubic meter of wood used stores the carbon from one ton of CO2 and also substitutes CO2 from the typically energy-intensive, non-renewable building materials that would otherwise be used.

Rubner has been working with the most sustainable building material by far for more than 70 years. Sustainability also means preserving and optimizing existing buildings. Whether for industrial or commercial construction, every professionally executed building renovation pays off in the long term. In Germany, for example, around one-third of the total energy demand is used for the thermal conditioning of buildings. The demand for heating is high and is often met in inefficient ways. Energy-efficient refurbishments offer significant cost savings through optimal insulation and extend the life of existing buildings. The increased living or working comfort and the associated higher user acceptance provide immediate benefits for the operator or investor.

The commissioning of the Augsburg-based company Rubner was prompted by the exemplary and successful implementation of the energy-efficient renovation of the comprehensive school in Wetter in 2015. This project served as a model for the renovation of another school in Hesse. The new project in Niederwalgern included the complete building envelope for the two four-story concrete skeleton structures from the 1970s. In addition to aesthetic improvements, an extension for a media library, an additional story, and the renewal of the building technology, the primary goal was to significantly reduce energy consumption using passive house-compatible components, thereby surpassing legal requirements.

A crucial factor in selecting Rubner was the requirement to carry out the renovation while the school was in operation. Noise and vibration-intensive work that occurred during school hours was restricted to break times. This was made possible by the proven, factory prefabrication of all construction elements. For instance, fixed glazing and windows were integrated into the façade elements under controlled workshop conditions at Rubner’s facility in Ober-Grafendorf, Austria. The advantage of this approach includes the highest possible degree of prefabrication, incorporating CNC machining and integration of building services under optimal climatic and technical conditions, ensuring quick and precise on-site assembly, and immediate weather protection.

The method is attracting attention: In preparation, the old reinforced concrete façade beams were dismantled, while the inward-set aluminum windows were removed only after the new façade elements were installed. The new façades were placed on their own foundations in front of the existing structure and anchored to these foundations to bear the vertical loads. To accommodate horizontal loads, additional glulam posts were mounted onto the existing reinforced concrete columns, compensating for tolerances of up to seven centimeters. For the ventilated façade, the wall element was constructed using a timber frame structure with various configurations. For structural reasons, the hollow box beam integrated into the wall elements was clad with OSB panels on both sides.

The large glass façades were integrated as post-and-beam elements. With a Ucw value of 0.8 W/m²K, the post-and-beam façade meets the high thermal protection requirements necessary for passive house compatibility. For summer heat protection and room darkening, electrically operated external venetian blinds are incorporated into the façade elements. The timber engineering specialists at Rubner in Augsburg, in coordination with the planners, developed the manufacturing and assembly concept, managed the production, transported all components with only thirteen truckloads, and assembled the complete building envelope. This project stands out as a showcase in every respect.

All pictures: © Rubner / www.krall-photographie.de