Window modules to upgrade energy efficiency of residential buildings with minimal disruption

August 20th, 2012 by Fraunhofer Institute for Building IBP

Fraunhofer Institute of Building Physics researchers have developed prefabricated multifunctional window modules to improve the energy performance of residential buildings that offer a more convenient alternative to the usual renovation methods, which can involve messy construction work.

“A form of minimally invasive intervention can be adopted by architects and builders for buildings in need of upgrading to modern energy-efficiency standards,” said Dr Michael Krause, a scientist at the Fraunhofer Institute for Building Physics IBP in Kassel, Germany.

A window module with surrounding insulation is simply inserted into the existing window opening (click image to expand - image ©Fraunhofer IBP)

He and his research team have developed a system of multifunctional window modules that could be used as an alternative to the usual renovation methods that can cause so much inconvenience to the building’s inhabitants.

The “Prefab” project is funded by the German Federal Ministry of Economics and Technology (BMWi).

Normally, building improvement work to reduce energy consumption and CO2 emissions is carried out by separate specialized contractors, including insulation and window installers, heating engineers, electricians, and plumbers. Sometimes these different tasks are not coordinated and this can result in construction defects, which can prolong the duration of the renovation project.

“The inhabitants of the building have to put up with noise and mess, especially if a new air-conditioning or heating system is being installed at the same time,” Dr Krause said

“Sometimes it is necessary to wait for the apartments to be vacated before the renovation work can be started.”

“Our multifunctional window modules enable on-site installation times to be shortened, considerably reducing the stress experienced by the tenants,” he said.

The window and window frame modules are equipped with a technical systems box and a surrounding insulation panel, consisting, for example, of a polystyrene-based composite system.

The self-supporting units are inserted in the existing window opening from the exterior, and provide additional external insulation around it.

An alternative version permits architects to use a solution consisting of a timber frame in combination with a mineral insulating material such as fiberglass or rock wool.

The removable technical systems box is located under the window sill. It provides room for installing components such as heat exchangers, decentralized micro-pumps for heating-system control, air filters, and even power sockets, ventilation channels, or Internet cabling.

Electrical wiring and water pipes are installed on the outside wall underneath the insulation panel and routed into the building through cutouts in the technical systems box.

Numerous additional activities such as installing cable conduits and plumbing systems thus become superfluous.

The entire unit, including the box, is delivered fully assembled by the window manufacturer, significantly reducing the on-site installation time.

Another advantage of installing all these components in an easily accessible box underneath the windowsill is that it simplifies maintenance.

If repairs are necessary, any component can be retrofitted or replaced immediately.

“By integrating heat exchangers and air circulation units in the renovation system, we can limit heat loss through the building envelope and ventilation.”

“By ensuring a high quality of workmanship, we can guarantee an airtight seal, avoid thermal bridges, and stop warm air escaping.”

“The new system reduces energy consumption because the insulation panels are constructed as self-supporting units. They are strong enough to envisage equipping them with solar collectors or photovoltaic cells,” Dr Krause said.

A demonstration version of the prefabricated, multifunctional window module, which was manufactured by the Institute’s industrial partner Walter Fenster + Türen in Kassel, is already available.

Dr Krause and his colleagues at the IBP intend to test the window modules in situ, in the renovation of a real building.

“In principle, they can be installed in many different types of building stock. We have decided to focus on multi-family residential housing dating from the 1950s.”


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