Smart, energy-saving glass solutions for large windows and glass façades

A lot of the energy transferred through the outer shells of modern buildings happens through glass windows. This energy transfer causes interior spaces to lose heat in winter and become uncomfortably hot in summer, thus increasing a building’s heating and cooling costs. While helping to keep interior spaces cooler in the warmer months, solutions such as blinds and shutters often affect light conditions and also detract from the spaces’ aesthetics. On the other hand, more advanced glazing solutions aiming to address the aesthetic problem are costly and consume a lot of energy.

To overcome these shortcomings, the EU-funded Switch2Save project is developing affordable, smart glass solutions that are suitable for large windows and glass façades. One year into the project, initial results have shown that these energy-smart insulating glass units (IGUs) can achieve as much as 70 % reduction in the primary energy use of buildings with extensive glazing.The Switch2Save smart glass solutions combine electrochromic (EC) and thermochromic (TC) window technologies with intelligent switching protocols. According to a press release posted on the project website, “EC switching relies on materials that change their light transmittance by applying a low electrical voltage, while TC cells are based on materials that change their infrared reflection properties with increasing temperature.”

Through these lightweight IGUs, the transfer of radiation energy can be easily controlled, therefore making it possible to substantially reduce the energy used for heating and cooling large buildings. A further advantage of this technology is the superior indoor lighting comfort it provides compared with conventional window blinds.

The TC and EC cells’ switching protocols were developed to set a switching strategy for the IGUs from bright to dark, with the ultimate aim of maximising energy savings, as well as visual and thermal comfort. To determine the optimal switching protocols, the project team used a virtual office building as their model. Based on this, they developed a switching strategy with three levels of automation: fully automatic, semi-automatic and predefined IGU operation. “The indicative implementation of the automatic switching strategy in the Switch2Save IGUs in two different climatic zones (Athens and Stockholm) suggests a variable heating-cooling energy saving potential between 10% and 70% in comparison to typical triple glazed windows with internal shadings,” the press release states.

“The developed models and simulations show that this switching protocol is able to optimize the switching behavior of our new IGUs, leading to the maximum possible reduction of primary energy use, ensuring or even improving visual and thermal comfort. We are pleased to present these results to the public in detail for the first time in our online workshop,” observes Dr John Fahlteich of project coordinator Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP in the same press release.

The Switch2Save (Lightweight switchable smart solutions for energy saving large windows and glass façades) solution will be demonstrated in two buildings: a large hospital in Athens, Greece, and an operational office building in Uppsala, Sweden. The project team will replace over 50 windows and balcony doors and 200 m2 of glass façades at these demo sites, following which it will conduct a year-long comparison of the buildings’ energy demand before and after the replacements.

For more information, please see:

Switch2Save project website