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


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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