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Refurbishment of a system-built, precast concrete school
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The Max Steenbeck Secondary School in Cottbus will soon move into this building, which dates back to 1974 and is typical of the system-built schools built in the former GDR. It will first of all be completely renovated and will become the new site of the school in 2012.
© Brandenburgische TU Cottbus, Lehrstuhl Angewandte Physik / Thermophysik
A secondary school wants to move. However, the new building is actually an old one. The double-winged system-built school with an assembly hall and gymnasium dates back to 1974. The precast concrete building is currently being gutted and renovated in accordance with the passive house standard. From 2012, it will become the new home of the Max Steenbeck Secondary School in Cottbus. The renovation project is considered to be a model for other schools since the building type is widespread in the region and the new school is relying on innovative concepts and technologies. District heating from a cogeneration system supplies the building with heat while electricity-efficient ventilation systems with heat recovery ensure hygienic ventilation that is energy efficient. The energy concept also includes other innovative approaches, for example decentralised heating pumps for distributing heat and the heat storage in the ground beneath the gymnasium floor.
Building summary
| Project status |  Projected |
|---|---|
| Location | Universitätsstraße 18, 03046 Cottbus, Brandenburg |
| Year of construction | 1974 |
| Refurbished | 2011 |
| Gross floor area | 10,863 m2 |
| Heated net floor area | 9,685 m2 |
| Gross volume | 41,669 m3 |
| Work places | 500 |
| A/V ratio before refurbishment | 0.28 m2/m3 |
| A/V ratio after refurbishment | 0.26 m2/m3 |
| Key aspects |
|
Project description
The Max Steenbeck Secondary School specialises in mathematics, sciences, computer science and technology. The school will move from its previous location into the new building as soon as the renovation work is completed. Located on an 18,800-m² site, the new school is situated directly next to the university campus on the north side of the city centre. The school, which is a system-built school with assembly hall, dates back to 1974. It is based on the last school system to be deployed, which utilised a combined wall and skeleton structure and was still frequently built until 1990. The use of central corridors, which is advantageous in terms of energy use, distinguishes it from the older system-built schools.
The school in Cottbus comprises a double-winged building with an assembly hall and gymnasium. The two three-storey wings, which each have basements, are linked to the assembly hall via a two-storey connection building and have 18 x 48-metre floor areas. The building is badly in need of renovation, particularly in regard to the thermal insulation, building services technology and windows. There are numerous leaks, cracks, concrete spalling and exposed reinforcement bars. The assembly hall and staircases are single-glazed. After 35 years of use, all the materials and building services equipment are fully worn out and to some extent do not work. The building is not wheelchair accessible. The building also fails to comply with fire regulations.
Research focus
With the accompanying building monitoring, innovative concepts and technologies are being investigated in order to test whether they can be applied and transferred to similar types of schools (see the explanation under “Energy concept”). The use of these concepts is being analysed in regard to technical and economic aspects. The two structurally identical and symmetrical school wings enable innovative components to be installed in direct comparison with conventional versions.
Renovation concept
The renovation of the building is aimed at achieving the passive house standard, which corresponds to a maximum heating requirement of 15 kWh/m² p.a. To attain this, it is being stripped back to the structural shell and then thermally insulated with passive house components.
The verification of the passive house standard as part of the passive house project package (PHPP) has showed that the heating requirement is more than 15 kWh/m² p.a. According to the current state of planning, the passive house standard is therefore not achieved. It is therefore being examined how the thermal insulation or system technology needs to be changed in order to nevertheless reach the passive house standard. The building does, however, clearly undercut the “3-litre house” standard in accordance with DIN V 18599, which defines a primary energy requirement of 34 kWh/m² p.a. as the upper limit for the heating, ventilation and auxiliary energy.
The generous central corridor concept with two three-storey school wings is being retained while the entrances are being furnished with additional porches. The previously opened courtyard area beneath the assembly hall is being enclosed and used as the new location for the canteen and library. The corridors are being opened to the windows on the gable ends and thus expanded to form breakout areas. In front of the basement level, an external area is being created for the adjacent music and art rooms. The installation of lifts will make the building accessible for wheelchair users.
Energy concept
District heating from a cogeneration system supplies the building with heat while electricity-efficient ventilation systems with heat recovery ensure hygienic ventilation that is energy efficient.
In terms of the building services technology, various innovative concepts and technologies are being deployed:
- Geothermal heat storage system for utilising surplus solar heat
- Brine geothermal heat exchanger to pre-temper the supply air
- Utilisation of heat from the district heat return pipe
- Small, decentralised, high-efficiency heat pumps
The two structurally identical and symmetrical school wings enable innovative components to be installed in direct comparison with conventional versions. For example, one of the two school wings will receive district heating from the conventional supply flow (70 °C), while in some areas of the other wing the district return flow is used (50 °C). Although this requires larger heating surfaces, the efficiency of the district heating system is improved. In addition, decentralised heating pumps instead of thermostatic valves will be installed on all radiators in this school wing. These will be controlled by means of individual room regulation in accordance with the timetable and thus enable rapid heating as well as other remote control functionalities via the bus system and building control technology. In addition, this eliminates the need for hydraulic balancing with throttle valves, which can be very complicated with larger buildings, causes flow resistance and energy losses and leads to differently warm radiators on each floor.
Geothermal energy is used for the two school wings, the assembly hall, the canteen and the library. 24 brine geothermal heat exchangers every 50 metres enable passive pre-heating of the supply air in winter and cooling in summer. The ventilation with an air volume flow of approximately 20 m³/h per person is regulated using time controls and presence detectors. Ventilation heat losses are minimised by means of heat recovery.
In the area of the gymnasium, it is planned to use part of the floor slab and the ground below it to store surplus heat and low temperature heat from the solar collector. For this purpose a pipe system with three loops is being installed in existing ducts under the floor slab. This will enable surplus heat to be diverted to the ground in summer. In winter, the system will make it possible to reduce transmission heat losses from the floor of the gymnasium. This is because the floor has only been recently renewed, which is why efficient thermal insulation is not possible for economic reasons. Based on dynamic simulation calculations from a comparable project, winter ground temperatures of around 18-20 °C can be expected, which will considerably reduce heat losses via the ground.
The lighting is also being optimised. Although the lights will continue to be switched on manually, automatic switching off at the end of each lesson will prevent unnecessary lighting and the associated use of electricity.
Performance
The operation of the building will be closely monitored for two years. For this purpose the bus system is being expanded so that the energy flows and system parameters can be recorded and stored at 10-minute intervals. It is also intended to enable web-based data retrieval in order to produce energy balances and to scientifically monitor the building operation.
In addition, comfort monitoring will be conducted whereby specific room parameters in a test room with PCM ceilings (such as the indoor air temperature, radiation temperature, airflow and air stratification) will be compared with the values of a reference room.
Information on this subject will become available as the project continues.
Optimisation measures and possibilities
Information on this subject will become available as the project continues.
Construction costs and economic viability
The renovation costs amount to 11.3 million euros. Half of this amount is being provided from funding programmes and the other half is being funded via a municipal credit scheme.
Information on this subject will become available as the project continues.
Educational concept
It will be possible to continue using the monitoring technology once the project has come to an end. For this purpose, the monitoring workplace will be integrated into the “UNEX student experimental laboratory”, which is available to all schools and will move into part of the ground floor. In addition to other student experiments in physics and chemistry, the building energy efficiency can be experienced experimentally, enabling the topic to be incorporated into the lessons of the scientifically oriented school as well as in events held by the BTU Cottbus. The current energy flows will also be depicted on a display panel in the school.
Information on this subject will become available as the project continues.
Key energy data
| Energy indices according to German regulation EnEV (in kWh/m2a) | before refurbishment | after refurbishment |
| Heating energy demand | 260.90 | 27.20 |
|---|---|---|
| Overall primary energy requirement | 214.30 | 45.20 |
| Measured energy consumption data (in kWh/m2a) | before refurbishment | after refurbishment |
| Site energy for heating and domestic hot water (dhw) | 133.20 | |
| Source energy for heating and domestic hot water (dhw) | 93.20 | |
| Total source energy | 132.10 |
All data refer to the school part of building with an energy reference area of 8048 m²
Implementation costs
| Implementation costs in €/m2 | |
| Construction (KG 300) | 650 |
|---|---|
| Technical system (KG 400) | 280 |
These figures represent estimated costs
Net construction costs (according to German DIN 276) relating to gross floor area (BGF, according to German DIN 277)
Refurbishment costs
| Refurbishment costs in €/m2 | |
| Total | 1.040 |
|---|---|
These figures represent estimated costs, According to Gross floor area
