Bremen State and University Library

Building summary

Project status
Location	Bibliotheksstraße 1, 28359 Bremen, Bremen
Year of construction	1973
Refurbished	2004
Building owner	Staats- und Universitätsbibliothek Bremen (+ Betreiber, Nutzer)
Investor	Zukunftsinvestitionsprogramm (ZIP)
Gross floor area	27.429 m2
Heated net floor area	25.011 m2
Gross volume	118.972 m3
Main usable floor area	20.794 m2
A/V ratio before refurbishment	0,19 m2/m3
A/V ratio after refurbishment	0,19 m2/m3
Key aspects	Optimised lighting, Ventilation + heat recovery, Active cooling, Regenerative + passive cooling, Control technology, operational management, building automation, Financing models, Optimisation of operations

Project description

Alongside the reference areas, the library from the year 1975 also has administration rooms, workshops, and a lecture theatre. In accordance with the concept of convenience and thermal comfort prevalent at that time, all areas in the building are automatically air-conditioned. Also typical of the time of construction is the facade with fixed glazing. The floor plan is of an almost square design, developed over 5 storeys. The generous reference area inevitably entails large deep rooms. This makes the building also very compact. The building structure is a reinforced concrete skeleton construction with a curtain wall facade. The intricate vertical subdivision of this facade is seen by the university as a distinctive design feature; therefore, it was requested that this be retained in the refurbishment. All measures had to be implemented during ongoing use of the building.

Refurbishment concept

The university's very high energy costs called for significant energy savings. The intention was to save over 50% of the original primary energy requirement. Also, library users complained repeatedly about the interior climate, unbalanced lighting, unopenable windows, the lack of possibilities to make adjustments, and permanent noise emission from the air conditioning and ventilation system. The refurbishment would also have to solve these problems. For the contractor, it was important to ensure a pleasant interior climate all year round, despite  reduced air conditioning equipment. Alongside the energy-oriented refurbishment, the entrance area was to be redesigned, and the interior decoration, as well as the technical and IT equipment in the work areas, was to be modernised. In the administration rooms, openable windows were installed. The neutral solar protection glass (g=0.38), used in combination with the existing sun protection elements, guarantees thermal insulation in summer. The thermal insulation of the roof surfaces was improved.

Energy concept

Demand-oriented (and thus energy-saving) control of heating, cooling and ventilation of different areas was not possible with the old air conditioning and ventilation system. During the refurbishment, the original air only system was dismantled, and replaced by three separately controllable systems for heating, ventilation and cooling. Rooms with exterior walls are now ventilated naturally. A small, controllable air conditioning system with enthalpy recovery ensures that air renewal in rooms with no exterior walls reaches the minimum level. Water is the medium now used to transport energy for heating and cooling. In the glass facade areas, conventional radiators were retrofitted, so the window fan system could be abandoned. At night and on weekends, the air conditioning systems can be almost completely switched off. The higher thermal loads arising in the building's interior are now compensated for by room cooling devices, for which the required cold water is partly provided via free cooling. The waste heat is simultaneously used for preheating of outdoor air via heat exchangers. Despite significantly increased light levels, the connected load of the lighting system was reduced by approximately 40% due to more efficient technology. The building's thermal insulation was significantly improved by replacement of the glazing, and insulation of the roof.

Performance

Experience gathered in the first year of operation after the refurbishment shows that the primary energy consumption was reduced from 831 kWh/m² p.a. in 2002 to 230 kWh/m² p.a., i.e. by around 70%. An accompanying socio-scientific user survey attested to a significantly higher level of user satisfaction than before the refurbishment.

Optimisation measures and possibilities

Due to initiated measures for optimisation of operations, even higher total energy savings are expected for the second year of operation (2006). Evaluation and optimisation will be completed by the middle of 2007.

Construction costs and profitability

The energy-oriented refurbishment cost 7.24 million euros. Much of this was financed by the German federal government's Investment in the Future Programme (ZIP). For the university's own share of the cost, there was initially no investment capital available in the budget. After detailed examination, the contractor rejected the idea of enabling complete financing by means of a performance contracting agreement. Instead, a municipal loan was arranged, to be paid off by means of the reduced burden on the budget which the energy cost reductions entail. Thus, the university itself took on the role of contractor, including the risks, but also the financial opportunities of such a procedure ("intracting"). As yet, due to the fact that the predicted savings were even exceeded, and that energy prices are higher than calculated, this is working out very we

Key energy data

Energy indices according to German regulation EnEV (in kWh/m2a)	before refurbishment	after refurbishment
Heating energy demand		85,00
Overall primary energy requirement		329,00
Measured energy consumption data (in kWh/m2a)	before refurbishment	after refurbishment
Thermal heat consumption	259,00	47,00
Total source energy	831,00	250,00
Power for lighting		35,00
Power for air conditioning plant		33,00
Heat for room heating areas		34,00
Heat for air conditioning plant		13,00
Cooling		7,00

Refurbishment costs

Refurbishment costs in €/m2
Overall costs	467
Energy recovery refurbishment of the building construction	69
Energy recovery refurbishment engineering	171
Modernisation, equipment	226

These figures represent established costs, Related to gross floor area

Operating costs

(Data according to main usable floor area)

Operating costs in €/m2a	before refurbishment	after refurbishment
Total energy costs	23,75	7,70
Heating	7,10	1,28
Total electricity consumption	13,38	6,01
Lighting	3,86	2,42
Infiltration/ventilation/cooling	11,15	2,64

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