Environmental dimension of sustainability in architecture means the conservation of resources through the optimized use of building materials and products, reducing the need for heating materials, electric power, etc. Socio-cultural dimension of sustainability in architecture means ensuring adequate comfort such as thermal insulation, lighting, soundproofing, etc. In Europe, for instance, potential energy savings for buildings are to be developed in a new version of the EU Directive on the Energy Performance of Buildings (2002/91/EC). The Directive, due to come in force in spring 2010, specifies amongst other things that all new buildings must be "nearly zero energy buildings" from 2021 onwards. The fulfillment of such high energy requirements make it indispensable to use innovative, energy-efficient building products. This applies especially to windows and façades (Building Envelope). Their performance largely depends on highly functional glass products which deliver highly efficient heat insulation, channeling light into the depth of the room where required.