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Frankfurt sets benchmark – construction of the first passive house school

Grundschule am Riedberg (primary school "Am Riedberg")

Background

The energy management of the city of Frankfurt has the challenging job of reducing the costs of energy, water and heating for its 1000 municipality buildings.
In spring 2003 the city council decided to build a primary school with a nursery using the passive house construction method. "Grundschule am Riedberg" primary school was opened on the 1st November 2004 after a construction period of 14 months. Since then it is identified as "Qualitätsgeprüftes Passivhaus, Dr. Wolfgang Feist" (certified passive house, Dr. Wolfgang Feist).


Building details

Gebäudetyp: Primary school
Year of construction/ Floor area/ Operating hours:
  • Year of construction: 2004
  • Floor area: The building complex consists of a primary school, with a capacity for 400 pupils, a nursery for 100 children and a sports hall. The school and the nursery building are constructed as passive houses with a total surface area of 6300m² at A/V 0,35.
  • Operating hours: The school is opened from 7.30 am to 1.30 pm and in case of events also in the evening. The nursery is open from 7.00 am to 5.00 pm.
Heating and cooling installed
  • 2 x kWB 60 kW sawdust boiler
  • 4m3 hot water storage
  • pellet reservoir
  • 30 kWp solar cells (PV) on the roof
Energy label/CO2 emissions The building was tested by Display® in 2004 and it performed as follows: energy and CO2 class A; water class B.

Project description

Aim _ The main objective of the building project was to achieve the passive house standard. _ Furthermore it had the following aims:

  • finding a rational and economic solution due to a low budget,
  • minimizing the total costs (sum of investment costs, operating costs for the next 50 years) at the given conditions of use,
  • developing or using an innovative and certified energy concept,
  • guarantee of the necessary air quality or air exchange without any loss of heat or comfort.


playground


Key points _ Because of the natural ‘heat output’ of children, schools and nurseries are generally predestined to be built as passive houses. For example, at an outside temperature of –12 °C the heat of 25 pupils and one teacher is sufficient to keep the classroom of a passive house warm.
Ventilation system and heat insulation: _ During the lessons, most heat gets lost by ventilation and not by heat loss through the walls. That is why in addition to the normal ventilation through the window, a mechanical basic ventilation system with good heat recovering was installed.

At the same time, this technique ensures that the air quality during a lesson is not seriously downgraded. The window’s U-value of about 0,85 W/m²K guarantees even pupils who sit near the window are comfortable. In order to use the daylight which comes from above, the lintels were minimized.

In addition to the passive house standard for insulation and an air density n50 of about 0,64/h heat loss through the floor are reduced by an insulated frost-protection tarpaulin. The summer protection from heat is realised by thicker wall construction, outside window shutters and night time heat loss.

The heating system: The heating system is quite simple and does not require maintenance very often. Small radiators, which are situated near the doors, heat the classroom sufficiently. The corridors are only heated by the air from the classrooms. On the sports hall’s ceiling, radiant panels were installed. This efficient technique guarantees a heat requirement, that does not exceed 15 kWh/m²a.

The heat production is realized by a fully automatic sawdust boiler plant (2x 60 kW). In bigger rooms there are temperature sensors. That allows these rooms to be heated separately. When the windows are opened, the temperature sensor cuts off the heating system.

Hot water and effluent water: _ For hot and effluent water a decentralised solution was preferred. Because during times of low water consumption, the circulation losses of hot water are higher if there is a central system, than the primary energy costs, needed to produce hot water electrically.

_ The decentralised and electrical hot water boilers are especially adapted for several requirements. The hot water supply is reduced to the minimum. Toilets and caretaker rooms only have cold water connections. Consumers who are situated far away from the central boiler, have their own electrical hot water boilers. The kitchen and sports hall are strategically situated near the central boiler plant and are supplied by it.
Electrical installation: _ Even the electrical installations are cheep and function on low-current requirements, according to the technical standards of the Hochbauamt (for further information please have a look at www.stadt-frankfurt.de/energiemanagement. You will find the document under "Dokumente">"Leitlinien" or "Deutscher Städtetag">"Energieleitlinien Planung"). That leads for example to a lighting system in the classrooms, which consumes 6 W/m² at 30 lux.

_ The solar photovoltaics on the roof were installed by an energy supply company who are still responsible for the maintenance. The solar panels are fixed by metal bars which are weighed down with gravel, so that the roofing did not have to be touched.

_ According to the passive house calculation with the "Passivhaus Projektierungspaket" (PHPP), the school’s primary need of energy is about 59 kWh/m²a.


court from above


Monitoring and evaluation: _ In order to evaluate the functioning of the building, a monitoring system was implemented, which will run for 2 years and be scientifically analysed at the end. In addition to that, the "Passivhaus Institut" measures the energy and cold water consumption, the air change rate at the entrance areas of the building, the efficiency of the ventilation system, the air quality and the temperature inside the classrooms compared to the outside conditions and the performance of the frost-protection tarpaulin.
Reason for inclusion as Shining Example _ The "Riedbergschule" is one of the first primary schools in Germany built entirely using the passive house standard. That is why this project can rightly be called a pioneer in this domain.

Furthermore, the "Riedbergschule" highlight the successful and exemplary energy management of the city of Frankfurt. The city council aimed to build as many new buildings as possible in the passive house standard. Altogether the city decided to achieve the passive house standard for 3 new elementary schools.

_ Last but not least, one has to highlight that the project was completed very quickly and with very few problems. From foundation till the completion of the project did not take more than 14 months.


Costs & Benefits

Costs & Funding _ The investment costs of the whole project amount to 16.7 mil Euro. In order to build the school in passive house standard, the extra costs amount to 5.3% of the construction costs (This is even 30-45% less than the "Energy Saving Regulation" dictates).

According to the energy costs of 2003, the pay back period of the passive house was estimated as 38,6 years (without any sponsorship). Through the augmentation of energy costs in the last three years, the pay back period is now reduced to 10 years.

_ The project received an aid of about 250.000 Euro from the "Deutsche Bundesstiftung Umwelt". A further 10.000 Euro were sponsored by the Land Hessen in order to finance the sawdust boiler plant, which cost 45.000 Euro.




main entrance of the school


Benefits _ Thanks to the passive house standard, the running costs of the building are very low. In 2003 the financial savings of the passive house amount to 570.000 Euro (present value) over a period of 30 years.

_ As a result of the reduction of energy consumption, it is possible to keep the CO2 emission quite low. Compared to the standard given by the "Energy Saving Regulation" (which already demands very low CO2 emissions), during the next 30 years the Riedbergschule can save 1000 t of CO2 emissions. The savings are even much higher if it is compared to the CO2 emissions of the already existing buildings in Frankfurt.

_ The energy savings of the school building compared to standard buildings of the city of Frankfurt (EnEV 30-45%) amount to 260 kWh/m² per year or 28.000 Euro per year.

_ The building needs 59 kWh/m² per year of primary energy for heating and electricity. The need of energy for heating alone is limited to 15 kWh/m² per year, which means a heating oil consumption of about 1.5 l/m² per year.

_ A further advantage is given through the compliance with the norm DIN 1946 T2 (limitation of CO2 concentration in rooms to 1500 ppm). This means better working and learning conditions for pupils and their teachers. The ventilation system ensures that the air quality inside the rooms does not degrade. In addition to that, this allows air humidity to be controlled the noise to be minimized.

Partnership details

Partners & roles _ Project management :

Hochbauamt der Stadt Frankfurt

_ Planning and architecture :

Architekturbüro 4a (Stuttgart)
Energetische Qualitätssicherung,

_ Energy quality management, energy concept :

Passivhaus-Institut, Energiemanagement Hochbauamt, Transsolar

_ Building services management :

ICRZ, Hochbauamt Stadt Frankfurt, Ingenieurbüro Rösch, SHL Planungsbüro

_ Structural physics management :

Kurz + Fischer

_ Static management :

Deutsch-Buckert-Thomas
Bauphysikalische Beratung, Baubegleitung, Zertifizierung und

_ Structural physics advice, Project manager, certification and measuring :

Passivhaus Institut Dr. Wolfgang Feist



playground - area of the gymnasium


Recommandations

Identification of obstacles overcome _ Main difficulties appeared regarding the detailed planning (standard structural physics management details) and construction. The management of construction during the building stage could have been better.
Lessons Learned _ Success factors for future passive house project are:

  • Well versed and engaged planner, who are specialized in passive house construction
  • Involvement of each planner already at the begin of the project
  • Energy quality management
  • Specifications regularly updated

    All in all the project is seen as a great success. At the moment the city of Frankfurt is building two other passive houses: the primary school Preungsheim and the nursery in Schwanheim. These municipal buildings should be trend setting! The objective has been confirmed by the new city council: In may 2006 the decision was made to construct all new municipality buildings if possible in passive house standard.


To know more

Organisation Hochbauamt der Stadt Frankfurt/ Energiemanagement
Contact Axel Bretzke
Phone +49-69-212-38697
Email axel.bretzke@stadt-frankfurt.de
Homepage www.stadt-frankfurt.de/energiemanagement/

Useful info

Link www.stadt-frankfurt.de/energiemanagement
Arrangements to visit Every year at the International Day of the Passive House and on request (have a look at our homepage)

 
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