Innovative solutions for the energetic retrofitting of historic glass and glass windows - practical tests in the Alte Schäfflerei, Benediktbeuern Monastery

Content and aims

From our point of view, historic buildings are worth preserving in their entirety. Essential components of their historic appearance include the windows and their panes, which still characterize the facades today. 

Within the scope of the project, the life cycles of glazing will be assessed. Key criteria are the consumption of resources, the expenditure of primary energy and the recycling rate. The latter deserves special attention. Due to different manufacturing processes as well as qualities of the raw materials used, historical glass panes usually have an unknown composition, especially with regard to heavy metals. Therefore, a return to modern production chains is not possible without further ado. As a result, large quantities of waste glass are produced. 

Secondly, the project will test the retrofitting of existing windows using the example of adaptively installed windows and evaluate the results using measurement technology. The test site for this is the Alte Schäfflerei in Benediktbeuern. The advantage of the retrofit variants would be the resource-saving preservation of the existing windows. Heat losses are minimized and thus the heat demand and CO2 footprint are lowered. 

Thirdly, the preservation of existing windows through minor modification of their structural and surface properties will be investigated. This includes proposals for modified frame constructions and the application of films and coatings.

The key questions of the project are: 
What is the relationship between upgrading existing windows to conserve resources and replacing them? 
What are the options for preservation?  

The project is thus closely related to the UN's Sustainable Development Goals (SDGs), not only with regard to the protection of cultural heritage, but also with regard to the efficient use of natural resources.

The aim is to develop solutions for the retrofitting of existing glass and window constructions from before 1960 so that they meet today's energy and monument preservation criteria and can continue to be used. Central fields of activity are the development of contemporary constructions and their model installation and metrological evaluation in the Alte Schäfflerei of the Benediktbeuern monastery. 
For the historical glass manufacturing processes, not only were the production sites and, where applicable, associated raw material sources determined, but process sequences were also compiled with regard to life cycle assessment. The use of firing agents and furnace designs also played a decisive role. 
The research results are supplemented by a guide. At the end of the project, the handbook is intended to show a suitable procedure for quality assurance in the handling of the stock and to take into account aspects of resource conservation and environmental balance. The transferability of the results to other building types plays a key role within the project. Finally, the findings will be didactically prepared at the Fraunhofer Center Benediktbeuern and visually presented to the general public. 

Research project video