Re-face: Refurbishment strategies for the technical improvement of office façades

Two thirds of all office real estate in Europe is older than 30 years. While the load bearing structure of a building can last for a century, the interior design is renovated at relatively short intervals. Practice has shown, however, that at the age of twenty to thirty years the facades and climate installations of a building do no longer fulfil today’s demands. They are out-of-date on technical, optical and comfort matters. Particularly these building components hold the potential to improve the energy performance of a building significantly. The façade of a building is also responsible for its exterior appearance and thus the public perception of it owner, as well as for the interior climate and the well-being of the occupant. Consequently, more and more office buildings come into consideration for refurbishment. However, currently the building economy is lacking innovative refurbishment strategies for office facades. On the one hand, most of the current renovation projects tend to substantially refurbish a building, which causes major interference with the building’s interior and the load bearing structure, and consequently a major investment. On the other hand, only little is known about the various façade types, which have been built in different eras. This leads to certain reluctance in initiating a refurbishment project. The market is obviously lacking an overview of practical refurbishment strategies and their applicability to different existing façade typologies. The present thesis intends to fill this gap of knowledge. After an introduction (chapter 1) and overview of the 'state of the art' of façade refurbishment (chapter 2), this research project is set up in four steps. In the first place, chapter 3 evaluates the existing stock of office facades in Western Europe. It defines the typical office facades and sorts them into 22 categories, which are characterised by structural features and similar refurbishment challenges. With this typology at hand, the distribution of these office facades is evaluated in different locations in the Netherlands, the United Kingdom, and in Germany. The local market analysis shows that the three countries, although being in the same climate zone, have developed very different office façades. Thus, an overview is created, which estimates the amount of facades of one typology for certain locations and eras. The common refurbishment tasks become evident. The following step (chapter 4) elaborates the demands and restrictions of façade refurbishment planning. In order to compare different concepts for one given building with each other, this chapter also evaluates existing assessment methods and generates appropriate tools for the special task of refurbishment. These tools compare the quantifiable features energy consumption and life-cycle-cost, as well as quality aspects such as the construction process and the interference with the function of an office, and possible improvement of indoor comfort. For these 'soft skills' an evaluation tool is developed, which facilitates the comparative rating and graphical visualisation. Chapter 5 takes in the central part of the research and intensively assessing five case studies that can stand representative for the most common façade types. Among these cases there are office buildings in the Netherlands and Germany, as well as the campus of Bielefeld University. In these studies, the typical problems of each façade typology come to light. For each case, different refurbishment concepts are developed and evaluated in order to define the most promising solution. These concepts look at the building in general and at the façade construction in detail. Furthermore, two product developments are part of this research, which propose solutions for the most common façade types. For the typical post-and-beam façade, an adapter profile has been developed, which permits upgrading existing façades of different manufacturers with new standardised products. It brings the façade to an up-to-date insulation level without alteration of connections to dividing walls and interior finishings. The second product development looks at the typical load bearing facades with window units. The concept proposes to replace the windows and renew the building services within the façade. By combining these features in new façade components it is possible to renew the building envelope and installations entirely from the outside with minimal disturbance of the interior. The system is highly modular, which allows future adaptations. In the fourth step (chapter 6) the results of the case studies and further assessed best-practice examples are combined. This thesis thus gives an overview of the common existing façade types and their typical challenges. The possible refurbishment strategies are evaluated in terms of architecture, function, comfort, investment, material consumption, and energy saving potential. It is possible to choose those refurbishment strategies that are most promising for the various refurbishment tasks. This analysis results in a matrix, which presents the features of each refurbishment concept and relates the concepts to the different existing types of façades. Thus, it will be of use for architects and specialist consultants in the early planning stage to clarify the building task and to identify the first refurbishment concepts. This work is also intended to provide decision makers, such as owners and investors with the necessary background knowledge of the topic. The façade industry can gain insight into the market for office refurbishment and can find inspiration for future product developments. With these goals in mind, this thesis aims to structure the complex task of façade refurbishment and visualise its possibilities. Thus, it wants to motivate real estate stake holders to step into the planning and initiate more buildings to be refurbished. The presented refurbishment strategies permit reducing the energy consumption of an existing building, while the life-cycle costs are reduced. At the same time, they give the chance to improve the comfort of the inhabitants and the quality of the urban environment. In this sense, the refurbishment of office façades takes its share in improving the sustainability of the building stock.