© REHAU AG

Close the window. Let fresh air in.

REHAU worked with ebm-papst to develop a ventilation system that provides fresh, warm air with closed windows.


Heat insulation is trending in Germany. But when heat stays in a house, moisture and contaminants stay in as well, and that promotes mold growth. To date, the remedy was provided by central ventilation systems or decentralized units built into a building’s structure. In cooperation with ebm-papst, REHAU AG + Co has now developed an elegant solution: a window with ventilation system and waste heat recovery built into the frame.

The solution faced two challenges: The fan, the heat exchanger and the control electronics all had to fit in the limited space offered by the GENEO series window frames, and the fans had to be as quiet as possible so as to avoid disturbing the residents.

ebm-papst suggested the use of an especially compact centrifugal fan, which the engineers developed in three steps. First they integrated a three-phase EC motor in the fan, which is used in home appliances due to its low noise level. Then, using flow simulations, they changed the number and angles of the fan blades to work out the best compromise between size and noise level. Finally, they adapted the fan to the available space and insulated it. “A window is supposed to last at least 30 years, so we use only durable and reliable components. So for this innovative new product, we looked for a company with an expert development team,” says REHAU’s Dr. Rainer Schork.

The main benefit of these self-ventilating windows, which are primarily intended for energy-saving renovations and new buildings, is that they can be installed quickly and easily. No air ducts need to be installed, nor is any masonry work required. Owners can perform maintenance work easily as they can replace filters and other components themselves. REHAU has already tested the windows in several pilot projects and recently began mass production. “The number of inquiries has already vastly exceeded our expectations. We’re very confident that the entire project will be a success,” says Schork.

How the ventilation system works

mag215_Lüfter-im-Fensterrahmen

In every window in the GENEO INOVENT line, two fan pairs for air intake and exhaust are integrated in the frame. While one fan routes the used, warm air from the interior through a heat exchanger to the outside, the other fan brings in cold outside air through the exchanger and preheats it. Using the waste heat in the outgoing air minimizes energy losses and lowers heating costs.

Read the technical article at mag.ebmpapst.com/techmag_window_fan

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