Almost only 15 % of Europe's windows contain energy-saving glass. EU-funded scientists are improving the energy efficiency of buildings and extending their functionality beyond the state of the art by promoting advanced glazing solutions.

Nearly 40 % of energy consumption in the EU goes to heating, cooling and lighting buildings. Their energy demands account for large amounts of carbon dioxide emissions. In the EU-funded project 'Harvesting solar energy with multifunctional glass-polymer windows' (HARWIN), scientists are developing new materials for producing advanced, multi-purpose windows. The improved solutions will reduce window weight, heat conductivity and energy consumption.

By using innovative glass-polymer composite materials, scientists are developing lightweight structures for glazing and window frames with tailored properties. The components of the new glass-polymer composite materials will allow a greater amount of light in the visible portion to pass through. Intelligent phase-changing materials will be capable of storing large amounts of energy. The new materials will also regulate humidity, decrease thermal conduction and ensure acoustic insulation. The challenge is to combine these functional characteristics into the new window pane with sufficient transparency.

So far, scientists have developed a lightweight glazing structure based on 2-mm glass panes that are laminated with glass-flake-reinforced polymers. A lightweight frame material has also been developed based on polypropylene. Other achievements have been the development of composite foils with visible transmittance around 95 % and improved stiffness, and of a new luminescent glass for down-conversion. Thanks to down-conversion materials, ultraviolet light is being converted into visible light. Refinement of the polyvinyl-butyral-laminated glass will further improve the hitherto-achieved degree of thermal conductivity of glass panes.

Scientists have demonstrated improved functionality of laminate glazing with the help of coatings, achieving a weight reduction of 25 %. Furthermore, they have shown the potential for further reducing the amount of glass needed for laminate glazing without compromising its mechanical performance.

Several laminated glazing elements of 0.5x0.5 square metres have been produced. Although their optical properties are good enough, the thermal insulation properties and the glazing weight need further improvements.

Project activities should contribute to a reduced greenhouse warming potential thanks to glazing and frame materials in windows and a lighter construction of buildings due to lightweight materials.

Anh Tuan