Giving old buildings a (almost) new lease of life

Research in focus September 2012

On a hot summer’s day, a visit to the Fraunhofer Center for Energy Efficiency of Historic Buildings and Conservation of Cultural Heritage Benediktbeuern (German website) always feels like a blessing. Pleasant coolness greets the visitor inside, behind the thick walls of the Old Cooperage of Benediktbeuern Abbey (German website). However, the same thick walls that make for refreshing coolness in summer make for a bitterly cold interior on frosty winter days. Until now, that is. Ensuring that buildings have appropriate insulation is a crucial factor for obtaining pleasant temperatures throughout the year and also for making energy savings. And this also applies to old buildings. But retrofitting insulation in these buildings, which is often a delicate task on account of their age, presents their owners and also planners and architects with major challenges. Tackling these challenges was the motivation behind a project in the Fraunhofer Center in Benediktbeuern. Over a period of several years, scientists from the Fraunhofer Institute for Building Physics IBP had tested various kinds of interior insulation for their applicability in old buildings. “This represents an important step in the further development and in some cases establishment of modern methods in the energy-saving renovation of old buildings,” explains project manager Ralf Kilian. And Christine Milch, building works and research coordinator at the Fraunhofer Center in Benediktbeuern, adds: “This project exemplifies in many respects the fundamental idea of what we want to achieve in Benediktbeuern. It is a wonderful example of how we can bring new technology to bear on old buildings while at the same time respecting historic preservation principles.”

If the walls of the Old Cooperage could speak, they would have an interesting tale to tell. The building was originally constructed in 1760 to accommodate the barrel-making shop for the abbey’s brewery, and continued to serve this purpose for many decades. Subsequent changes in the use of the historic building bear witness to turbulent times. For example, families of refugees moved into the upstairs rooms at the end of the Second World War and lived there until well into the 1950s. In the latter years before Fraunhofer IBP took over the building and established the Fraunhofer Center for Energy Efficiency of Historic Buildings and Conservation of Cultural Heritage in July 2010, the ground floor housed a smithy and the abbey’s janitorial services and building maintenance shop. “Naturally, the previous occupants had made various structural alterations and renovated parts of the building from time to time, but the historic preservation aspect was never the main focus of these undertakings,” says Milch. This has changed under the direction of the former Preservation of Historic Monuments and Preventive Conservation working group in the IBP’s Energy Efficiency and Indoor Climate department.

The Fraunhofer Center in Benediktbeuern is a long-term research project involving an extensive range of construction measures. While it has been renovated in a way that satisfies historic preservation and energy-saving imperatives, it was a “glass building site” that served as an educational object. “Here we want to investigate traditional and innovative techniques for use in heritage buildings and other old buildings that are worth protecting,” explains Milch. The biggest individual project was the painstaking restoration of the roof, which involved retaining as many of the old roof tiles as possible and firing new ones to match the original design, as well as replacing the rotten beam ends and the shed dormers – all following historic preservation and restoration principles. Further structural measures followed, such as insulating the ceiling below the attic and repairing the façade.

The "interior insulation project", for which funding has been granted by the German Federal Ministry of Economics and Technology, has been one of many aspects of the research that had been carried out in the course of renovation work at the Fraunhofer Center in Benediktbeuern. In keeping with the experimental nature of this project, which did not focus on any particular type of insulation, the walls of the over 200-square-meter upper story had been lined with ten or eleven different insulating materials. Given the historic importance of the building, any changes must be reversible. “This means that we have had to ensure that the installed insulating materials can be easily removed without causing any damage to the masonry or, failing that, only minimal damage that can be quickly repaired,” explains project manager Kilian. The first preliminary tests were carried out in one of the test houses at Fraunhofer IBP’s outdoor testing site in Holzkirchen. In addition to taking damage-free removal into account, the scientists involved were also committed to using either very thin materials with very good heat-insulation properties or else insulation made from renewable raw materials or recycled material.
To this end, the scientists have compiled a portfolio containing three insulating material groups:
1. Mineral insulation systems, based on materials such as calcium silicate, clay, or brick.
2. Insulation made from renewable resources (for example, wood fibers, cattail or other plants of the Typha genus, cellulose, hemp, or flax) or from recycled material (for example, polyurethane from car seats).
3. Thin insulation systems (for example, vacuum insulation panels or aerogel blankets).

“Sample measurements and computational analyses had been carried out on the building before, during, and after the insulation measures in order to compare the advantages and disadvantages of different systems and determine the practical limits of each application,” says Kilian. “Our objective is to determine which thicknesses of insulating material were acceptable and suitable without risking moisture damage and the associated health problems or damage to the fabric of the building.” At the same time – in order to consider the issue of sustainability as thoroughly as possible – the Life Cycle Engineering department carried out a life cycle assessment of the individual insulating materials. “With innovative approaches, new materials, and interdisciplinary cooperation, we will be able to generate valuable scientific data, which can then be put into practice,” says Kilian. 

However, plenty of work has been done at the Fraunhofer Center in Benediktbeuern, for example: a roof demonstration center was created in the north end of the building; various wall heating systems had been studied in relation to energy, exergy, and hygrothermal aspects; and an elevator was installed to improve barrier-free access within the building. The focus of all activities at the Fraunhofer Center in Benediktbeuern will be on networked, interdisciplinary cooperation with various institutions and project partners. “The interactive element is very important to us,” explains Christine Milch. “We want to create a lively and active center, and so we have founded our work on four pillars: research, demonstration, acquiring knowledge, and spreading knowledge.” To meet these objectives, a program of regular seminars and public information events has been launched. “These do not merely address scientists, but also tradesmen, contractors, and interested members of the general public,” says Milch. “But we would especially like to inspire young people and want to organize specific events for them.” An educational exhibition had been created bit by bit, which documents the individual steps involved in restoring the historic building and make the results of Fraunhofer IBP’s research more generally available. 
“Historic buildings are more than just bricks and mortar. They are windows to the past and also an important part of our present and our future. As such, they help us to define our historical and cultural identity,” says Milch.

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