The use of wide expanses of glass in modern, energy-efficiency focused architecture requires holistic planning as well as multi-disciplinary cooperation between architects, technical planners and facade installers.


For some years now, glass has characterized modern architecture like no other material. Provided they are incorporated in an overall planning concept in line with their performance potential, glass materials not only characterize the appearance of facades but also make a decisive contribution to the energy efficiency of buildings. Based on experiences acquired with initial major projects involving a high percentage of glazing, the aspect of thermal protection in summer plays an especially important role today. Solar protection devices compensate for a disadvantage that often goes hand in hand with the transparency of glass architecture – much to the architects' regret – the undesirable build up of room temperature in summer. The use of the latest generation of coated solar protection glass can substantially reduce but not entirely avoid this effect. In winter, these solar gains are desirable by all means but in summer they can result in unpleasantly high air temperatures in building interiors.

Optimized Interplay

To avoid the undesirable heat build-up in interiors, a wide variety of solar protection systems are installed in glass architecture. They are an essential component for the productive interplay between efficient thermal protection, maximum use of daylight and reliable ventilation of interiors. Controlling the complex correlations between external and internal influences on the building in such a fashion that pleasant temperatures prevail indoors throughout the year, is one of the biggest challenges for modern glass architecture. Prof. Anton Maas, Head of the Construction Physics Faculty at the Kassel University, forecasted that solar protection in summer would increase in importance while also stressing the performance of windows and facades as highly efficient energy "winners" suitable for saving massive amounts of heating energy.

The glass facade of the Düsseldorf Stadttor is a twin-skin structure. The internal element facade with timber windows that can be opened and the outer glass skin in 12 mm TSG is set off by a 1m wide climate buffer. Air supply and exhaust openings are located at floor/ceiling level. Photo: Messe Düsseldorf

Experts principally agree that integral planning is required to efficiently leverage the energy and architectural potential of large-surface glazing in building skins. Planners and facade installers must, where possible, already cooperate in the development stages of a project. Only this multi-disciplinary collaboration and the consideration of the given climatic conditions at the location can ensure an optimised interplay of summer-time solar protection, ventilation and heating and/or cooling technologies.

New Opportunities through building-integrated PV

Building-integrated or to be more precise facade-integrated photovoltaics will also play an increasingly pivotal role in boosting energy efficiency in the future. Although numerous product solutions are already available in the market, installed systems can only be found in isolated cases. The reason for this is lack of consideration on the part of architects – something which solar industry experts discovered at the international Solar Summits congress. Even so PV modules can now be installed as systematically as conventional facade elements made from other materials.


Against the background of the amended European Directive on Total Building, efficiency facade-integrated photovoltaics will necessarily gain importance. The Directive requires a Near-Zero-Energy Level for newly erected public buildings from 2019 and private buildings from 2021 with the remaining energy requirements being largely met by regenerative sources. This provision will drive the development of corresponding systems and give architects the incentive to include integrated PV elements in their planning concepts.

Even today PV elements featuring the latest thin-film technology can be ordered in various colours thereby providing more design freedom for facades. Prof. Eike Weber, Director of the Fraunhofer Institute for Solar Energy Systems ISE, assumes that these new coloured solar cells will bring the desired breakthrough for building-integrated photovoltaics over the next few years. These cells, which were co-developed by the ISE, are based on completely different principles to the semi-conductor technology used so far. Since the technologies for their production are very similar to those already used in industrial glass processing, efficient manufacturing is possible. In addition to their use in new building integration-enabled photovolatics modules also have multiple applications in facade refurbishment.

The glass facade elements of the Capricorn Haus in Düsseldorf are multi-functional. Next to each countersash window with integral solar protection there is a 1.80 m high red glass panel. It conceals a facade module with cooling, heating and ventilation functions including heat recovery as well as lighting, sound dampening and interior acoustic elements. Photo: Messe Düsseldorf

Comprehensive Market Overview

Knowledge of the available glass products and their working principles is imperative for realising sustainable, energy-efficient glass architecture. Only by considering any glass versions that qualify for a building project can multi-disciplinary cooperation come up with holistic building concepts that live up to the high requirements made by both legislators and building owners. Glasstec the world's biggest trade fair for the glass provides an excellent overview of the latest developments in glass facades.