News – What`s happening in energy research

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The window module with the insulation edging can be inserted in the old window gap.
© Fraunhofer IBP
Prefabricated, multifunctional window elements

Window module shortens building refurbishment

When residential buildings undergo energy-oriented refurbishment this often entails prolonged construction measures. However, the researchers at the Fraunhofer Institute for Building Physics (IBP) in Kassel have now developed a new window element that is designed to shorten the installation time. The prefabricated, multifunctional components also enable conventional renovation processes to be optimised. 

"Buildings can be refurbished in a minimally invasive manner and carefully modernised in terms of their energy efficiency," says Michael Krause, a scientist at Fraunhofer IBP. In the "Prefab" project, the researcher and his team have developed multifunctional window elements that are intended to replace conventional but laborious renovation methods that can be particularly burdensome for the residents. Until now, the construction measures designed to reduce energy consumption and CO2 emissions have been separated according to the respective trades, such as the facade, window and heating installation and electrical and plumbing work. However, these individual measures are often not coordinated with one another and can lead to construction faults and long refurbishment times. "The installation of plant-related components such as ventilation and heating systems can particularly impair the living quality of the residents. It is often even necessary to wait until the apartments are empty before conducting the necessary repair work," explains Krause. "With the multifunctional window elements we can shorten the installation times on site and considerably reduce the stress for the tenants."

Prefabricated modular components

In addition to the window and the window frame, the element consists of a technology box and insulation edging, which can be produced as a thermal insulation composite system made of polystyrene. This self-supporting module is inserted into the old window gap from outside and insulates the old facade in the window area. As an alternative to the thermal insulation composite system, architects can also use a timber frame structure with mineral insulation such as glass or rock wool. The technology box is located beneath the windowsill. Within the removable box it is possible to install components such as heat exchangers, decentralised heating micro-pumps and ventilation filters as well as electrical connections, ventilation ducts and Internet cables. Electric cables and water pipes are laid across the outside of the facade under the insulation and, via inlets in the technology box, are connected with the inside of the building. This eliminates the need for numerous works within the building such as laying pipes and cables. The window manufacturer supplies the elements including the technology box preassembled, which considerably accelerates the installation process at the building. A further advantage: Because the windowsill can be opened, this enables all components to be easily maintained, retrofitted or replaced, such as when repair work is required. "Integrating the heat exchanger and the ventilation technology within the refurbishment system enables us to reduce heat losses caused by the building envelope and the ventilation. In addition, the sound design of the system prevents air leaks and thermal bridges, i.e. the heat cannot escape to the outside. All in all we lower the energy consumption," summarises Krause. Last but not least, the support structure of the insulation elements makes them very stable, so that it is even possible to cover them with solar collectors.

The prefabricated window element is already available as a demonstrator. It has been manufactured by an industrial partner in Kassel. In the next stage the Fraunhofer researchers want to test the facade element under real conditions in a residential building requiring refurbishment. Although in principle it can be installed in many different existing buildings, the researchers have particularly set their sights on early post-war apartment blocks. The project is being funded by the German Federal Ministry of Economics and Technology.



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