Low-tech ventilation for double-glazed facades
Philipp Molter and his team at the Associate Professorship for Architectural Design and Building Envelope at the Technical University of Munich have, together with the facade company Frener & Reifer, developed a ventilation system for double-glazed facades that opens automatically when the temperature rises above a certain value and closes again when it becomes cooler.
Efficiency thanks to less technology
The heart of the Ventflex technology developed by Molter is a paraffin-filled thermal cylinder. The wax-oil mixture inside the cylinders expands when the temperature rises above a certain value. The increase in volume generates a pressure that pushes the cylinders apart like telescopes. If the temperature drops, they contract again. Until now, thermal cylinders have only been used to open and close ventilation slots in greenhouses. In his research project, which has just been completed, Molter is able to show that the technology is also suitable for cooling double-glazed facades efficiently, cost-effectively, energy-efficiently and without the need for complex electronic control systems.
Thermal cylinders control the low-tech facades
The elements of the new low-tech facade do not differ visually from conventional facade elements. However, the outer pane of the double-glazed box window is not fixed, but connected to the frame at all four corners via the thermal cylinders. If the temperature between the panes rises above 23 degrees Celsius, the cylinders push the outer glass-front 5 cm outwards. The slot between the frame and pane allows cooler outside air to enter and naturally ventilate the space between the panes occupied by the heated sun protection. If the temperature drops below 23 degrees, the gap closes again automatically. The reaction time is only a few minutes. In winter, the facade module remains closed on cold days to prevent the offices from cooling down.
Positive energy balance
Simulations at the Chair of Building Technology and Climate Responsive Design at the Technical University of Munich show that the new low-tech concept is very efficient: Compared with modern facades, up to 50% of the energy required for heating and cooling can be saved. For high-rise buildings from the 1970s and 1980s, which have not yet been renovated and therefore consume a lot of energy, the savings can be considerably greater.
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