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Building Construction
The building of the Bremen state and university library is a concrete skeleton structure with a curtain wall facade. An exterior metal frame construction includes fixed and movable louver blinds. In some areas concrete cladding had been applied without any additional insulation. Window frames had some thermal insulation, the original glazing had a U-value of 2,8 W/m²K.
Interior partitions were lightweight constructions tiled with coated chipboard. Suspended ceilings had slats of coated sheet metal.
The superposition of different floor plans results in several roof areas and ceiling soffits. These areas had been insulated using expanded polystyrene. While the U-value of the roof garden was only 0,84 W/m²K other roof areas had a U-value of 0,48 W/m²K.
The building had a surface to volume ratio of 0,2 m^-1.
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Heating / Ventilation / Cooling and Lighting System
The building was fully air-conditioned without operable windows. Heating, cooling and humidification was exclusively provided by supply air. The building had 10 air handling units with maximum loads from 4 000 to 91 000 m³/h. Exhaust fans were typically separated from these plants. Heat recovery was not installed. The heating load was 5.000 kW, the cooling load 3.200 kW. In the perimeter area 2 pipe induction units were used, additionally an air-curtain was installed at the windows. Some of the plant allowed vitiated air to be recirculated. Steam humidification was used. The air flows before retrofitting significantly deviated from the design levels.
Ceiling mounted luminaires mostly equipped with two 38 W fluorescent lamps and magnetic ballasts had been installed. A few incandescent lamps were still in use. The installed specific lighting load was 20 W/m².
Problems / Damages
Generally the building was in a good state of repair. The main problems – high energy consumption and poor user acceptance – were on a conceptual level. Since heating, cooling and humidification could only be provided by the ventilation system, the air change rate was significantly higher than necessary. This resulted in a high energy consumption. The pneumatic control system did not allow optimisation of the HVAC system operation. The HVAC system included no possibility to link the energy consumption to the individual plants. Users complained that private offices have no operable windows.
In some areas the lighting level was too low and the space appeared dull although the specific electric lighting load was high. In window areas glare could not be controlled efficiently.
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