Two French companies, construction giant, Vinci and solar specialist, Sunpartner Technologies, have formed an equal joint venture to produce a smart-glass window that can generate electricity, become opaque, sense its surroundings and communicate over the internet. According to Sunpartner, this combination of qualities can cut a building’s energy consumption up to 30% by reducing its exposure to sunlight and therefore its need for air conditioning. The ability of the window to alter its opacity in response to external conditions can be controlled by a building management system or by smartphone app. The Horizon windows can passively save energy and actively generate it. Sunpartner has invested €8m euros on a factory for the Horizon windows. Production is scheduled to begin in the first quarter of next year, and it is forecast to rise to 150,000 square metres a year. It is expected that the market supplied by this output will reach $3.5bn by 2020. The companies say that the capital cost of the window will be the same as a traditional system, but that it will be 20% cheaper to clean and maintain.