Well protected under a pyramid of special glass from Glaverbel

Construction of this attractive new building in Ulm's historical city centre was completed only recently. The building is located right next door to the historical town hall on the bustling marketplace, and it shows that, with the right planning, new and old can set each other off perfectly. The potentially shocking impact of such a large, imposing structure erected there using conventional building materials underlines just how important the choice of glass was as a material in its design.

The brief for this project was to not visually overpower the beautiful old town hall, but at the same time to preserve the character of the surrounding squares and narrow streets. The urban planning objective and aesthetic aim was to produce a solitaire on this conspicuous site that would meet the highest standards. A functional area of 3,600 m² was created to house approximately 220,000 media items. Ulm's central library provides an excellent solution to the problem of using the old without getting carried away with the new.

Construction and access
The building, erected over a frame construction, had a grid dimension of 6.6 m by 6.6 m. The glass skin covering the entire construction was designed as a double glass façade from the third storey upwards.
Access is gained via the main entrance on the east side of the building that opens onto the marketplace. The side entrance, which doubles as a staff entrance, can be reached on foot via the amphitheatre-style steps on the west side of the building.
Inside, a central staircase spirals around two lifts, providing access to the upper floors. A fire escape and a book lift complete the ensemble.

Vertically, the building is divided up into the ground floor, on the same level as the marketplace, a basement with workshops and a lecture room in the west wing, the library levels on the first, second and third floors, offices on the fourth floor, and a readers' café on the fifth floor, affording an exquisite view over the city.

Design of the façade
The building is entirely enclosed in a glass skin that exactly follows the shape of the building, which resembles two overhanging square stories topped with a glass pyramid. From the third floor upwards, the sloping glass is a double façade.
Ingenious measures ensure that a comfortable temperature can be maintained inside the building all year round without high energy costs. Indeed, the coating of Glaverbel's Sunergy solar control glass, combined with the outer layer of patterned glass, allows only a small amount of solar radiation to enter the building.

Moreover, the accessible double façade design acts as a useful climatic buffer. Large ventilation flaps and a moveable sunshade between the two skins of the façade prevent the building from overheating and protect against glare in sunny weather, as well as cooling the structural components with colder night air in order to avoid excessive cooling loads. The outer skin of Glaverbel glass is one of the key features of the building. The outer layer is made of laminated safety glass comprising:
- an outer sheet of 10-mm toughened screen printed glass (colour: RAL 7040 window grey);
- a 1.52-mm PVB film interlayer;
- an 8-mm inner sheet of Sunergy Azur solar control glass coated in position four.

The outer sheet is fitted flush with the façade between the vertical supports via cut-out sections measuring 4 x 18 mm (see figure.). Horizontally, the sheets were sealed with high-quality silicon. The 3,500 m² of special glass used in the pyramid guarantee safety, residual load-bearing capacity in the event of breakage, solar control, an aesthetic appearance and a high level of transparency. The optimally successful glass construction won the Wings of Glass Award in the category of Most Original Building Structure (old – new).

The library's construction called for a solar control glass with low external reflection (7%) that would blend in with its historical setting. In addition, it had to be possible to toughen and laminate the glass, which had to have high light transmission (50%) and a low solar factor (38%, value for non-screen-printed glass).

The product selected was Sunergy, the only solar control glass on the market with a hard pyrolytic coating, a low level of light reflection and a neutral appearance. Other pyrolytic coatings were unsuitable because their external reflection was too high. Soft coatings could not be used either, because they couldn't subsequently be toughened or laminated.

All requirements were fully met by Glaverbel's glasses, produced in cooperation with BGT in Bretten, which did an excellent job of the screen printing, toughening and lamination processes.