Practices

Grundschule and Gymnasium Reutershagen: Plus-energy school retrofit

A Subliniat Caz July 2016
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The Reutershagen schools; Europaschule Gymnasium Reutershagen secondary school and the Grundschule Reutershagen Nordwindkinner primary school have been grouped together in one educational center. The pupils are now taught in one centrally located building rather than attending two different school sites in the Rostock suburb of Reutershagen. This school is comprised of a new build as well as a refurbished (in terms of plus-energy efficiency) existing building. The new school has taken on diverse extracurricular activities which have consequently placed considerable demands on a flexible room use.  As a result, a new spatial concept was also developed as part of the energy-based refurbishment.

 

The secondary school was previously housed in two identical school buildings that were located, respectively, in Mathias-Thesen-Strasse 17 and Bonhoefferstrasse 16. The original buildings were constructed around 1960/61. As of October 2015, all primary and secondary school pupils attend the refurbished plus-energy school building “Grundschule und Gymnasium Reutershagen” in Mathias-Thesen-Strasse.

 

According to the energy-plus standard, the entire school complex is designed to generate more energy than it actually needs for space heating, domestic water heating, lighting and for running the technical building systems. To provide higher thermal insulation for the solid external walls of the existing building, timber elements were mounted on the external facade. The area between the new annexed constructions (primary and secondary school classrooms) and the existing building (main building classrooms) were covered with a transparent roof and used as an unheated intermediate climate zone. The energy supply is based on district heating combined with an Organic Rankin Cycle (ORC) power plant, a solar Building-Integrated PV (BIPV) system and two wind power plants.

 

The design of the new external envelope which combines the existing external construction components and efficient building technology, will minimize the energy requirement while simultaneously expanding the usage possibilities. The project provides an exemplary model of replication for schools with similar characteristics located elsewhere.

 

 

Location

 

Mathias-Thesen-Str. 17, 18069 Rostock, Germany

 

 

Project team

 

Project name: PLUS-Energieschule Rostock

Building owner: Hansestadt Rostock Amt für Schule und Sport

Project management and architect design: Institut für Gebäude + Energie + Licht Planung, (IGEL), Wismar

Structural engineering: IPS Ingenieurbüro für Baustatik Dipl.-Ing. Peter Schenk, Wismar

Systems engineering: K&S Ingenieurplanung GmbH, Rostock

Energy concept: Fraunhofer Institut für Solare Energiesysteme (ISE), Freiburg / Fraunhofer Institut für Bauphysik (IBP) Abteilung Wärmetechnik, Stuttgart

Simulation and monitoring: Kompetenzzentrum Bau, Mecklenburg Vorpommern, Wismar

 

 

Time schedule

 

Built: 1960-61

Design: August 2008 – August 2010

Building renovation: August 2010 – August 2015.

Construction phases:

  • August 2011 - October 2012: Expansion of the primary school and buffer zone “Marktplatz” (intermediate climate zone)
  • October 2012 - August 2015: Expansion of the secondary school, buffer zone "Schulstraße” (intermediate climate zone) and renovation of the main building
  • August - October 2015: Validation measurements and monitoring
  • Spring 2016 (still pending): Completion of outdoor area and new construction of sports hall building (see design draft)

 

Delivery: October 2015

 

 

Surface areas / building use

 

The Grundschule und Gymnasium Reutershagen consist of 3 three-storey building sections which are arranged around an indoor schoolyard ("Schulstraße” and  “Marktplatz” areas). This unheated intermediate climate zone has been created between the buildings and is made of a timber structure with a transparent covering of glass. This alledged buffer area divides the resulting larger building into climate zones while at the same time provides double-sided connections with communication, circulation and recreational areas. Each building section use is described below:

 

Main building (South): the only existing construction that has been retained where multipurpose rooms and large classrooms are located. This section faces south and makes up the front view of the complex.
Grundschule Reutershagen Nordwindkinner (West): New construction where primary school classrooms are located.
Europaschule Gymnasium Reutershagen (North): New construction which is parallel to the main building and has the same length. Secondary classrooms are located here.

 

The original two single-storey buildings (sports hall and nursery) were demolished and a new sports hall has been built. No data on new build has been provided up to date.

 

 

Values

Before renovation (each building)

 

After renovation

Total Constructed Area (m2)

5.258

9.136

Total Usable Area (m2)

4.697

7.032

Total Conditioned Area (m2)

3.422

4.159*

Total Non-Conditioned Area (m2)

1.275

2.798*

Total Volume (m3)

26.709

26.629

Total Conditioned Volume (m3)

-

16.892

A/V ratio (1/m)

0,4

0,38

Airtightness

-

0,4

(*) Usable floor area according to German standard EBF – Energiebezugsfläche.

 

 

 

Renovation costs

 

Total cost: 11.8 M € (net 8.8 M €)

 

Public investment support (applied only to the eligible actions):

 

65% Bundesministerium für Wirtschaft und Technologie (German Federal Ministry of Economics and Technology) according to support program “Energetische Verbesserung der Bausubstanz” (Energy Improvement of Buildings)
25% Landesministerium für Energie, Infrastruktur und Landesentwicklung (Federal State Ministry of Energy, Infrastructure and Regional Development) according to support program “Aktionsplan Klimaschutz” (Climate Protection Action Plan)

 

 

 

Envelope performance

 

With the exception of the walls in the intermediate zone, the main building keeps the existing façade composition with solid masonry structure, but it has been completely thermally insulated with timber cladding. Double windows are installed on the south and east side. The existing pitched roof structure will be built back to form a flat roof which has been correspondingly sealed and insulated. The floor plate is insulated with PS rigid foam and vacuum insulated panels.

 

The new building sections adjacent to the buffer zone are constructed using a plate structure made of lime-sand brickwork and reinforced concrete slabs, whereby the roof structure and the internal walls have been executed using a lightweight structure. Wood-aluminum windows have been used.

 

 

U-values (W/m²K)

Before renovation (each building)

 

After renovation (renovated parts)

After renovation (new parts)

External wall façade

1,06

0,15

0,15

Wall of intermediate climate zone

-

1,70-1,90

0,15

Windows (wood frame)

2,80

0,80

0,80

Windows (plastic frame)

2,60

-

-

Ground floor

-

0,34

0,27

Roof

1,91

0,12

0,12

Roof of intermediate climate zone

-

1,96

1,96

 

Composition details:

 

 

-External wall façade:

Before renovation: 430 mm brickwork, plastered on both sides
After renovation (renovated parts): 15 mm interior plaster / 430 mm brickwork / 84 mm timber post structure / 240 mm mineral wool between the timber posts / 16 mm wall insulation / 30 mm vertical support battens / 30 mm counter battens / 24 mm vertical boarding
After renovation (new parts): Prefabricated timber modules: plasterboard / 4 cm insulation / timber frame construction with 24 cm mineral wool insulation

 

-Wall of intermediate climate zone:

After renovation (renovated parts): 17.5 / 36.5 cm plastered solid brick.
After renovation (new parts): Pulley construction of sand-lime brick masonry

 

-Windows:

After renovation (renovated parts): Double windows with heat-insulating glass
After renovation (new parts): triple glazed wood and aluminum windows

 

-Ground floor:

After renovation (renovated parts): vacuum insulated panels
After renovation (new parts): 10 cm polystyrene foam insulation

 

-Roof:

After renovation (renovated parts): 24 cm mineral and vegetable fiber insulation (WLG 035).
After renovation (new parts): 28 cm mineral and vegetable fiber insulation (WLG 035).
Roof of intermediate climate zone: 3-layer glass with ETFE film cushions.

 

 

 

Energy consumption

 

Energy consumption values (kWh/m²a)

Before renovation (each building)

 

After renovation

Heating and DHW (Final Energy)

398,9

84,6

Heating and DHW (Primary Energy)

103,7

21,7

Electricity (Final Energy)

21,4

57,8

Electricity (Primary Energy)

14,7

39,7

Total Final Energy consumption

420,3

99,4

Total Primary Energy consumption

161,5

61,4

Ventilation system
(incl. Power supply)

 

 

33,3

(*) Average values are measured over 3-year consumption data related to total conditioned area (1.659 m2 before and 4.008 m2 after) and the primary energy factor for heating network is 0,26.

 

 

 

Energy systems

 

Centralised and balanced ventilation system using heat recovery

The centralised ventilation plant is regulated by a demand-responsive control system. Each space can be controlled separately as every room has been provided with a CO2 sensor. The air is supplied through textile air-hoses, reducing the flow noise and introducing the supply air free from draught. The stale air from the classrooms passes into the unheated corridor (buffer zone) which is located between the two buildings. From there, the exhaust air is centrally extracted to the ventilation units which recover heat from the air and transfer it to the supply air.

 

Heat emission into spaces provide by wall and ceiling heating systems

There are two systems that are intended to transfer the heat into the spaces: (1) a wall heating system, which generates the energy required to cover the base load and heats the spaces up to a temperature of about 17 °C, and (2) a ceiling-mounted radiant heating system to provide further heating for the spaces.

 

Summer heat protection

Summer heat protection is ensured by external blinds. Additional PV modules are mounted above the windows, serving as a permanent solar protection.

In the summertime, when indoor air temperatures are high, the ventilation system will be operated briefly at night in order to discharge the high thermal load. Night-time ventilation via windows is not possible, as the windows must remain closed at night for safety reasons.

 

District heating system combined with ORC plant

The Building is connected to a district heating network in Rostock, supplying the building with heating at a low temperature level using a transfer system. The heat from the district heating network, supplemented with a solar thermal system, is used to produce electricity using an Organic Rankine Cycle power turbine specialised for these low temperature differences.

 

Electricity production

A PV system (138 kWp) and two wind power plants (3.5 kW each) are installed on the roof of the building. The electricity generated by the PV modules is entirely fed into the public grid, while all of the electricity that is produced by the wind power plants is consumed on site. When wind is not available, the ORC plant produces the electricity needed.

 

 

 

Awards and recognitions

 

Award in the category “Restoration” from the BMWi Prize 2014 "School 2030 - Learning with Energy” with the title “Renovation of the school in Reutershagen to plus energy school” (http://www.enob.info/fileadmin/media/Forschungsfelder/Begleitforschung_Schule/Schule_2030/2_Rostock/2_Poster_Rostock-Reutershagen.pdf)

 

 

Additional links

 

Project description: http://zebau.de/fileadmin/Redaktion/Bilder/Veranstaltungen/4._Passivhauskonferenz/121128_C1_3_Ingo_Volmering.pdf

 

Project status: http://www.koe-rostock.de/projekte/plus-energie-schule.php

 

Case study of Renew project: http://www.renew-school.eu/wp-content/uploads/2014/10/7_Reutershagen_folder.pdf

http://www.iea-ebc.org/fileadmin/user_upload/docs/TD1406/15_IEA-EBC_Technical_Day_June_2014_-_Rostock_PLUS_Energy_School_Mainka.pdf

Lessons learnt

The project can be transferred to other schools as this type of building is widespread in the former East German federal states and also exists in a similar form in the West German federal states. The intermediate climate zone is envisaged as a flexibly used recreational and communication zone and also provides a suitable space for exhibitions and joint activities. These could include spatially based experiments, sporting activities, art exhibitions and musical performances. This area will be heated only by means of passive solar gain and exhaust heat.

Award labels

Available link languages

Funding description

The city of Rostock pays for the renovation, subsidies were granted by the German Federal Ministry for Economic Affairs and Energy and by the federal state, Land Brandenburg.