The community hall is a two storey reinforced concrete construction. The external walls are made of 24 cm thick concrete. In some areas the walls of the lower level have a layer of 11.5 cm sand-lime bricks in front. Some other wall areas (both levels) on the inside were lined with 3 cm insulation panels. The U-values lie between 0.83 W/m²K and 4.70 W/m²K. The flat roof was insulated with a 6 cm insulation layer. In the lower level between the floating floor and the concrete fundament are 3 cm insulation panels. The U-value being 0.95 W/m²K. The windows had wooden framing and a U-value 2.5 W/m²K.
The kindergarten construction is a mixture of in-situ concrete and prefabricated components. The roof and upper floors are built on concrete beams which run from inside to outside and pose problems as thermal bridges. Three apartments make up the upper level while the kindergarten is in the lower level. The apartments cover approximately 40% of the kindergarten. The flat roof and windows are the same as described above for the community hall. In front of the upper level’s reinforced concrete wall is a curtain wall. The 5 cm space is filled with insulation panels. The lower level’s walls are insulated on the inside with 3 cm panels.
The rectory is also a reinforced concrete construction. There are three levels. The exterior walls for the two upper levels are constructed from an inner layer of 14 cm concrete, a 6 cm insulation layer of polystyrene and an outer layer of 7 cm concrete. The U-value is approximately 0.55 W/m²K. The 24 cm thick reinforced concrete walls of the lower level have a layer of 3.5 cm thick insulation panels. Inner walls from heated to non-heated zones are only partly insulated. The flat roof has an insulation layer of 6 cm. The U-value being 0.57 W/m²K. The windows are similar to the other buildings and in the floor of the lower level is a layer of 3 cm insulation. In Figure 6 can be seen the site plan while in Figures 7-9 the buildings before retrofitting can be seen.
One problem was the large energy losses due to the long and poorly insulated piping between the buildings and losses in the heating transfer station. Another problem was the openings in the building envelopes. A Blower door test for the kindergarten (without apartments) measured an air change by 50 Pa of 4.8 ACH. The main problem was around the window frames and at the ceiling connection to the outside. In the rectory 3.1 ACH was measured with the main contributor to the air leakage being the windows, external blinds and sliding doors.
Previous Heating, Ventilation, Cooling and Lighting Systems:
The buildings of the community centre are heated by district heating. The delivery takes place in the installations room in the community hall. The house installations are connected directly to the district installations without heat exchangers between. From the installations room the church, kindergarten and rectory are then supplied. The pipes are either in installation shafts or run directly through the earth. In all buildings the heat is distributed with radiators. In the church is additionally floor heating. In the rectory is a 130 l DHW tank while in the kindergarten there is a 200 l DHW tank which is for the three apartments as well as the kindergarten. The DHW tanks are both located in the installation rooms of their respective buildings and heated by the district heating. In the community hall both apartment and hall DHW heating is electric.
The concept was the theme of an architectural competition. The energy reduction aims were set as an outline for the competition. After the competition the draft plans from the architect offices Günter Hermann and Gesellschaft für bauphysikalische Objektplanung (GFO) were used as the basis for the final conception. In the final conception planning the following institutions and offices took part
- Katholische Kirchengemeinde „Zum Guten Hirten“, Ulm-Böfingen
- Fraunhofer-Institut für Bauphysik, Stuttgart (IBP)
- Bayrisches Zentrum für angewandte Energieforschung e.V. (ZAE Bayern), Würzburg
- T.P.I. Trippe + Partner, Karlsruhe
The ZAE Bavaria was responsible for the planning and installation of the vacuum insulation panels, whereas. Trippe + Partner was responsible for electric and heating installations. Over several workshops including IBP and representatives of the community centre Ulm-Böfingen the final planning took place. The calculated heating energy demand was made by GFO.
Retrofit System Description:
For the community hall insulation could only be added to the inside of the external walls as a prerequisite was that the exterior facades remain untouched. Additionally there could be no change to the inner side of the foyer north wall, as no change in the room usage was possible. Only the walls under the windows on the south side could be removed. The apartment was left untouched. On the inner side from the exterior wall 10 cm mineral wool replaced the existing insulation. The replaced south side walls received a rear ventilated curtain facade with 10 cm insulation. The roof insulation was replaced with 22 cm hard foam insulation panels. In the lower level of the building apart from the corridors all the floors were renewed with an insulation thickness of 7 cm. The windows were replaced with wooden framed double low-E glazed windows.
The entrance area of the three apartments over the kindergarten was closed of with glass. A part of the terrace was incorporated into the living space. These two measures meant that the concrete beams did not reach the outside anymore. For all exterior walls a new curtain wall system with 14 cm insulation and fibre cement elements was installed. The roof is the same as for the community hall while the windows have triple instead of double low-E glazing as in the community hall. Due to space constraints 2 cm thick vacuum insulation panels were laid in the classrooms and the activity room.
For the rectory the external layer of concrete and insulation was replaced by a curtain wall system with 3 cm vacuum insulation panels and fibre cement elements. The external wall of the stairwell was covered with a 8 cm composite heat insulation system. In the lower level walls between heated zones and non-heated zones were insulated with 6 cm insulation on the cold side. The windows and the roof were insulated as in the kindergarten.
Heating Ventilation and Lighting Systems:
In the community hall the delivery station in the installation room was adapted and rebuilt to include a heat exchanger between the house installations and the district heating installations. All pumps were replaced with differential pressure controlled pumps. The room temperature control system was connected to window contacts so that when windows are opened the room heating switches off. The radiators along the south facade were replaced. The ventilation system was removed. All lighting was replaced with low energy lighting. The electric installations were updated. Photovoltaic collectors were installed on the roof and the south facade.
In the kindergarten all pumps were replaced and room temperature controls were added as described above. The insulation on the connecting hot water pipes between the community hall and kindergarten was replaced. Solar collectors were installed on the roof to heat the DHW. A supply and exhaust ventilation system with heat exchanger controlled by room VOC gas detectors was installed. Lights and electric installations were handled as described above.
For the rectory the heating circuit was adapted and replaced as required. Radiators were replaced on the south facade. Pumps and room temperature are controlled as above. Installation piping between community hall and kindergarten had the insulation replaced and improved. Solar collectors were installed on the roof to support the DHW heating. An exhaust and supply ventilation system like in the kindergarten was installed. The lighting and electric installations were also handled as described above.
Resulting Energy Savings:
Two heating periods 2006 – 2007 were measured. The values used in this paragraph are the average from the two years and have been climate corrected (HDD for site/measured HDD*Energy consumption). The period 01.03.2003 – 29.02.2004 before the renovations took place is used as a comparison. The apartment in the community hall had an increase heating energy consumption from 24% while the church showed a slight decrease of 2% from before the renovation. This is while neither was renovated. The kindergarten had a saving of 48% while the saving in the rectory was of a similar magnitude at 53%. The largest saving was in the community hall were there was a 73% reduction in heating demand. When comparing the total primary energy for all energy consumers for all three renovated buildings there is a reduction of 43%.
In the community hall (without apartment) the electricity consumption rose from 15.4 kWh/m²a measured before the renovations to 30.4 kWh/m²a in 2006 and 25.3 kWh/m²a in 2007. This is despite the low energy lighting. Investigations into why resulted in several possible causes. The activity rooms have a significant increase in usage since the renovations. The visualization and data logging systems for both years account for 3.4 kWh/m²a. Unknown at the time was that two garages (one of which is a separate building but connected to the community hall’s electricity net) were heated with electric radiators and no one could say whether they where heated during the earlier period measured before the renovations. In the kindergarten (without apartments) the electricity consumption also significantly increased from 15.3 kWh/m²a measured before the renovations to 22.6 kWh/m²a in 2006 and 22.1 kWh/m²a in 2007. The explanation was in this case clear to see. The new ventilation system that was new accounted for 7.9 kWh/m²a in 2006 and 7.6 kWh/m²a in 2007. When deducted from the total consumption a small reduction in the rest electricity can be seen. In the rectory over a 100% increase in electrical power consumption was measured. Before renovations 9.4 kWh/m²a was measured, 19.9 kWh/m²a in 2006 and 25.0 kWh/m²a in 2007 were measured. The difference between 2006 and 2007 is because the apartment was empty for the first half of 2006. The difference between before and after was also investigated. One cause was the ventilation system that was not there before the renovations which accounted for 4.5 kWh/m²a. Another reason was the increased use of the offices and office aids e.g. computers, printers.
- Funding: National Support Program EnOB: German Ministry of Economy and Technology (BMWi), Projektträger Jülich (PTJ).
- Project Coordination: Günther Hermann Architects, Stuttgart;
- Energy Concept: Fraunhofer Institute for Building Physics (IBP),
- Building Physics: Company for Building Physics Object Planning (GFO), Krefeld;
- Heating Technology: T.P.I. Trippe + Partner Engineering, Karlsruhe;
- Monitoring: Fraunhofer Institute for Building Physics (IBP) Stuttgart; Bavarian Centre for Applied Energy Research (ZAE), Würzburg;
- Case Study Authors: Johann Reiss, Michael Beckert, Fraunhofer Institute for Building Physics (IBP), Stuttgart