In fact glass plays a central role across Europe in the attainment of high energy-efficiency standards in many low-energy houses.
Modern glazing solutions are more energy-efficient than non-transparent materials, as glass lets solar heat into the house for free (g value) and at the same time offers good thermal insulation (U value). In this way, increasing the area taken up by high-performance glass surfaces can contribute to heating and reduce the need for cooling. Furthermore, correctly oriented windows improve daylight autonomy and reduce the need for artificial lighting. Depending on the local climate, a ratio of glazing to living area of between 20 and 30% is optimal for good daylight autonomy and for ensuring high energy efficiency. It is not surprising, therefore, that the most energy-efficient and sustainable buildings constructed in Europe over the past few years have had above-average levels of glass surfaces.