Fenstermaschine I & II – Prefabricated Renovation Windows with Integrated Technology: “Window Machine” & Demo Project

According to a forecast from 2015, around 230,000 new homes per year are to be created in Germany over the next few years and the requirements for building envelope renovation are much greater. Germany's population is increasing and residential construction activity is growing. Forecasts assume that this rising demand will stabilize in the coming years. At the same time, climate policy, which aims to reduce energy imports and greenhouse gases, offers economic potential for Germany. The two projects “Fenstermaschine” (window machine) and “Fenstermaschine II” (window machine II) dealt with the topic of an accelerated, disruption-minimized construction process with the integration of typical window technology, but also with the integration of building technology into the window element for typical buildings from the 1950s to 1970s.

The aim of the window machine is an industrially prefabricated complete system for window installation in both renovation and new build projects. It includes all circumferential connection points around the window, e.g. between window and external thermal insulation composite systems (ETICS), window and existing masonry, window and roller shutter box, etc. Other systems are also integrated into the window machine in modular design. While exterior wall constructions and thermal insulation glazing are now of high energy quality and fully developed, design, construction, building physics, functional and organizational problems are concentrated between the window and the wall. The construction process for conventional window replacement is made more difficult by the interfaces between the trades involved at geometrically and physically demanding points. Thus, “complaints in the area of (window) connections to the building structure are one of the most frequent features in legal disputes in construction.” [STI 2009]

The window machine is based on the principle of the window frame, a circumferential component into which a window is inserted, a construction method that has not yet gained widespread acceptance. Apart from a few suppliers, window frames have generally been developed on a project-specific basis to date. In line with the idea of prefabrication, the window is planned as an integral part of the element. Although the use of purchased window elements would allow for a wide variety of solutions, it contradicts the desired simplification and standardization of the overall product and thus the rationalization of the manufacturing process. If the principle of the window machine becomes widely accepted, the variety of solutions will increase due to the number of suppliers.

As part of the first project, 3 variants of a prefabricated window module for refurbishment were developed and then tested in a second project using a demo building. The following key aspects and components were taken into consideration:

• Simplified construction process / modularity
• Adoption of tolerances from the existing building
• Relocation of the window level to a new insulation level
• Opening types / electric opening of the windows
• Influence on daylight / natural ventilation in the interior
• Effects of new materials on insulation and cladding
• Integration of:
  • Sun, blind and privacy protection
  • Insect protection
  • Mechanical ventilation
  • heating
  • Photovoltaics
• Life cycle: manufacture - installation – recycling