Built for the sun: Solar thermal collectors as architectural elements

The application of renewable technology in buildings offers one of the greatest hopes for reductions in fossil fuel consumption, and the use of solar thermal for architectural integration has enormous potential. Christian Fink, Thomas Mueller, Charlotta Isaksson and Dagmar Jaehnig report on some examples from this rapidly growing sector.

Solar collectors are an excellent technology for heating spaces and producing hot water. Modern solar thermal systems not only meet high technical standards but are also becoming increasingly used as architectural design elements in roofs or facades, as can be seen from the multitude of such systems constructed to date.

Solar thermal is a mature technology and its reliability is evident from the ever-increasing number of newly built houses with systems installed. In addition, the use of solar plants has gained increasing importance in the provision of hot water and for space heating in large-volume buildings such as apartment blocks and hospitals, as well in as the hotel and restaurant industry and many kinds of industrial buildings.

The blue facade of this apartment building in Tyrol, Austria shows that collectors do not always have to be black holleis, austria

Indeed, the time when collectors were tacked on to buildings for the sole purpose of producing energy have long since passed. Today, collectors can be used for a range of additional functions such as protection against the elements, providing shade and thermal insulation. In fact they have become a completely new element in architectural design. The solar industry has already reacted to these trends and now offers optimized solutions for the architectural integration of collectors into the roof and facade, including a variety of colours, shapes and materials.

In this article we will look at some of the main ways of integrating solar thermal into buildings, including roof and facade-mounted systems. It will also go on to discuss some examples of building-integrated solar thermal systems in Austria, Germany and elsewhere.

The collector as part of the roof

The most basic types of built-in systems known as in-roof collectors can be integrated simply and quickly into the cladding of the roof. Here, the individual modules with surface areas of up to 16 m2 are fastened directly to the battens of the roof. Collectors can be supplied in a wide range of sizes and shapes, and made fit to the exact shape of the roof. This is a relatively simple process and helps to keep costs within limits.

Facade collectors – active and passive gains

Increasingly, solar collectors are being integrated into the facades of buildings. In this position they can not only generate energy, but can also take on design functions. What’s more, they are much more visible than when mounted on the roof. Accordingly, facade collectors have level, and sometimes structured, surfaces, which can be coated to provide further architectural features.

Since the architecture defines the dimensions used in the design of the facade, collectors with specially tailored dimensions are the rule rather than the exception in this market.

Home for disabled people in Salzburg, Austria, with solar domestic hot water and space heating aks doma, austria

More and more, architects are coming to grips with the new challenges and possibilities associated with integrating sustainable technologies into the fabric of their buildings, and increasingly looking at renewable technologies like photovoltaics and solar thermal. Facade collectors become a part of the external skin of a building and take on the functions of protecting and sealing the building from the elements. Non-rear ventilated facade collectors also contribute to lowering transmission heat losses since the absorbers warm up even at low levels of sunlight in winter, thereby reducing the temperature difference between the internal space and the outer walls of the building.

Questions to do with the physics of buildings and above all to do with condensation on the rear wall of the collectors, have now been intensively researched and answered. The solar industry offers specially designed facade collector modules, which can be integrated into the building shell with no condensation concerns.

Multi-family building in Dornbirn in Austria with facade integrated solar collectors aks doma, austria

Up until now, solar collectors have always been black for maximum absorption of radiation, which did not always fit in with the aesthetic of a particular building. New developments in coatings mean that coloured collectors are now available with only low losses in collector efficiency. Practical examples of these collectors demonstrate the path towards a successful combination of architecture and sustainable provision of heat using solar plants.

Six sample buildings in Austria, Germany, France and Norway

Six built examples of buildings with facade and roof-integrated collectors and collectors, some of them integrated during retrofit, are discussed below. These aim to illustrate how solar thermal collectors can be a part of a building.

Facade integrated collectors in Salzburg, Dornbirn and Oslo
The first example is from Salzburg, Austria, where a solar thermal system has been installed to provide energy for domestic hot water preparation and space heating in a home for disabled people. In this case the solar thermal collectors have been integrated in the building facade, as can be seen in the image above. The architect, Josef Brandmüller, wanted to provide the building with clean and sustainable energy and solar thermal collectors were the first choice. Speaking about the project he said: ‘An all-too technical appearance as a result of the facade integrated collectors was avoided through the selection of wooden window frames. In addition, safety barriers in front of the balconies and windows were installed in coloured glass to soften the appearance and provide a positive atmosphere.’

Terraced houses with solar domestic hot water preparation and space heating in Oslo in Norway ståle skogstad

Another example of facade-integrated solar thermal collectors is in a multi-family building in Dornbirn, Austria, which uses solar for domestic hot water preparation and space heating. The architects Roland Gnaiger and Udo Mössler described the homes, saying: ‘The collectors are directly integrated into the building. It constitutes the south-west facade and integrates the windows in the winter garden. Further, the black, reflecting glass surface is “art for construction” – it is continued on the ground in the form of a water surface reflecting the black colour of the collectors.’

Collectors can also be curved and therefore can fit ideally into the shape of the roof, as shown in this manufacturing hall in Berlin, which is a listed building. energie solaire s.a., switzerland

The final example is of a terraced house with solar domestic hot water preparation and space heating in Oslo, Norway. The solar collector facade combines an innovative heating system with modern design, providing green energy, high comfort, a healthy indoor climate and ultimate user-friendliness for the inhabitants. The solar collector facade helps give the building an architecturally modern and stylish design. The dark, reflecting surfaces are attractive building elements, simultaneously giving life to the building’s south-facing facade, producing energy and acting as a barrier to road traffic noise. The architects (Christian Dahle and Kurt Breitenstein, Norway) said: ‘It is important for the integration of solar thermal building elements that standardized industrial products, such as solar thermal collectors, in the design work are accepted by the architect. The building and construction sector’s development of industrial products and building methods should never be an obstacle, but a challenge for good architecture.

Solar collectors form the entire south side of the roof of this apartment building in the Tyrol, Austria, and emphasize the appearance of energy-efficient buildings Arch mathoy/tisun, austria


The integration of solar collectors can also lead to additional functions. The modules in this apartment building in Graz, Austria provide shade for the uppermost row of balconies aee intec, austria




Roof integrated systems in Hamburg Bramfeld
Solar collectors were integrated in the roofs of terraced houses in Hamburg Bramfeld, Germany, to prepare domestic hot water with solar energy. The Austrian architect, Tobias Weiss, thinks that the applied solar technology is a positive component for the project: ‘The pretty location inspired the architect to develop 18 terraced houses and two storey residential buildings. The urbanistic design follows the topographic profile very well. Four rows of terraced houses were oriented north-south and slightly displaced so that a good view is possible for all the inhabitants. The aesthetic integration of the solar collectors was shown to be a profitable assignment for Architect Phillipi (Hamburg, Germany). He took the creative opportunity to use the large continuous roof area available to integrate a total of 3000 m2 solar collector area. The collectors, as they are integrated into the roof, have a positive architectural effect and thereby an influence on the building’s architecture.’

Balcony-integrated solar thermal collectors siko, austria


Roof integrated solar thermal in Hamburg Bramfeld wagner & co solartechnik gmbh


Retrofit collectors in Liepzig and Val Thorens
Integration of solar collectors during a retrofit was realized in Leipzig, Germany – a multi-family building with collectors for solar domestic hot water preparation integrated into the balconies. This 11-storey multi-family residential building, originally built in 1973, was constructed with precast concrete slabs, and has 167 apartments. It was renovated in 2004-2005 and ensuring an energy-focused renovation was a priority. The facade was given a ‘face-lift’ with added insulation and nine pre-fabricated balcony blocks, on which the solar thermal collectors were mounted.

Multi-family building with solar domestic hot water preparation in Leipzig, Germany schüco international kg


Coloured absorber coatings for solar thermal collectors can place an emphasis on the facade aee intec, austria

In Val Thorens in the French Alps, a multi-family residential building was renovated in 2001 with the addition of solar domestic hot water technology. Architect J.P Chiantello, described it: ‘The existing facade and the balconies were very worn by the rigorous climatic conditions at the high altitude. The new metal “crowning” of the roof, which protects the architectural elements of the facade, made it possible to integrate solar collectors in the south side of the building and to fit harmoniously in the sculptural play of the cover.’

A multi-family residential building in Val Thorens in the French Alps retrofitted with solar thermal panels clipsol



Christian Fink, Thomas Mueller, Charlotta Isaksson and Dagmar Jaehnig work for AEE INTEC in Gleisdorf, Austria,
website: www.aee-intec.at.

The examples in this article were gathered within the EU-supported project ’NEGST’ (New Generation of Solar Thermal Systems). The overall objective of ’NEGST’ is to provide a framework for research in order to bring more cost-effective solar thermal systems, particularly for domestic hot water preparation and/or space heating on the market. This is necessary in order to contribute to the European Union’s Action Plan with regard to the reduction of CO2 emissions and the cost-effective supply with renewable energy sources.

Part of the project ’NEGST’ is concerned with the evaluation and preparation of efficient methods of integrating solar thermal collectors into buildings.

See the project homepage for more information:

NEGST is a project financed by the European Commission DGTREN within FP6.


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