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A former military base on its way to a zero energy city

EnEff:Stadt - Forschung für die energieeffiziente Stadt
Already refurbished residential buildings with solar energy systems and prefabricated wooden façade refurbishment elements

Already refurbished residential buildings with solar energy systems and prefabricated wooden façade refurbishment elements

© B&O Wohnungswirtschaft, SCHANKULA- Architekten/Diplomingenieure

Settlement summary

Neighbourhood
Project statusProjektstatus: Phase 3 Realisation
Location of local communityStadt Bad Aibling, 83043 Bad Aibling, Landkreis Rosenheim, Regierungsbezirk Oberbayern, Bayern
Developer, organizerB&O Wohnungswirtschaft GmbH & Co KG München
SettlementNeighbourhood: former military area
Utilisation typeMixed area: Former military base, future neighbourhood with mixed utilisation – residential, commercial and services, tourism
Settlement size [ha]70
Gross floor area (according to DIN 277) before refurbishment [m²]72.000
Residential space before [m²]23.500
Industrial, commercial area before [m²]34.500
Area of social infrastructure before [m²]9.000
Number of accomodation units before183
Number of jobs in neighbourhood before800
Age structureApproximately 60 % built between 1915 and 1948, approximately 40 % post-war buildings, German construction regulations did not apply to the American military base.
State of construction and refurbishmentBuilding condition: good, thermal insulation unsatisfactory, building services equipment outdated
Heating systemGas/oil district heating centre to be converted
Ownership structureB&O Wohnungswirtschaft (Housing Company) is the majority owner. Some of the real estate will be owner-occupied, some rented and some sold.
Project themes

Project description

Initial state

The area is supplied with heat by a gas or oil-fired local heating station with 3 6,500 kW boilers, resulting in a total of 19.5 MW.  This local heating system was thoroughly refurbished in the mid-nineties and is in a good condition. This heat generation system is significantly oversized overall, and the building or block transfer stations are equipped with excessive technology in unnecessary performance classes. A 6.5 MW boiler was shut down and a second was downsized from 6.5 to 3 MW.

Dimensions and quality

Currently, the total residential space is 23,500 m². There is 34,500 m² of office and commercial space. There is also 9,000 m² of space used for social institutions (kindergartens, schools, medical care) and 5,000 m² of catering services. The total residential space and usable floor area is 72,000 m², divided among 52 building complexes or residential complexes.

Calculations based on the German Energy Saving Ordinance (EnEV) 2007 state a final energy requirement of 351 kWh/m²a and a primary energy requirement of 459 kWh/m²a for a typical residential building in the development area. By contrast, the EnEV primary energy requirement specification is 130 kWh/m²a (for refurbishments). The figure is similar for office buildings. Overall, the planned refurbishments at EnEV new building levels (= 71 % of the old building limit), low-exergy and passive house standards will achieve potential savings of significantly over 50 %.

Objective

This objective will be achieved by implementing high energetic standards and using innovative technologies, utilising modern project management methods and modern planning instruments. In addition to this, the entire energetic system of the city district is to be monitored systematically.

Energy concept

The developer and investor, B&O Wohnungswirtschaft, has decided to hydraulically separate the entire project area into a North and South Network and to establish a solar-powered local heating network with decentralised feed-in points in the North Network. A balanced, zero fossil fuel energy target is still being aimed for in the North Network. In addition to improvements in the demand side, this is to be achieved by means of a woodchip boiler, extensive solar thermal collectors, a large-scale, ground-mounted photovoltaic system and a PV system on the roofs of the former aircraft hanger.

In order to optimise energy generation, two concepts were developed as alternatives to boiler modernisation and continued use of existing equipment:

  1. Solar grid feed-in at 100 % summer demand coverage, CHP plants for the base heat loads for heating, existing gas boiler for winter peak loads.
  2. Solar feed-in to the network, seasonal solar storage tanks, domestic hot water backup heating via decentralised heat pumps, use of the existing gas boiler when the solar storage tanks are empty and the heat pump coefficient of performance is unfavourable, i.e. flexible heat generation according to demand and conditions.

An existing barrage of the Moosbach river for hydroelectric power generation should also be taken into consideration for the energy supply to the neighbourhood.

Energy balances

The energy balance plans are limited to the northern part of the development area (North Network). To produce a final energy requirement balance (heating, hot water, auxiliary and user electricity requirements), data previously used to size the North Network and selected energy-based key data from 15 residential and commercial buildings in the area were used as a basis. Taking into account the assumed transmission losses and the electricity consumption of the heat pumps, the final energy requirement is estimated 2,350,000 kWh p.a. for heating, 468,000 kWh p.a. for the building services electricity consumption, with a total electricity consumption of round about 885,000 kWh p.a. For the balancing, four versions were investigated that differ in terms of the use of additional renewable energy generators (solar thermal collectors and the hydropower plant on the Moosbach river, or alternatively photovoltaic systems in the overall area), and for which either the German Energy Saving Ordinance (EnEV 2007/2009) balance limits apply or alternatively are expanded by additionally incorporating the user’s electrical consumption.

Conclusions regarding the balancing: Without taking into account the photovoltaic systems, which strictly speaking do not belong to the North Network balance area, it is not possible to achieve a zero energy balance. In terms of the primary energy balance, however, the North Network area with its 15 buildings and supply structure is 30% better than, for example, the passive house limit value of 120 kWh/m² p.a. (according to EnEV). In addition to most of the buildings having a good energy standard, this is due to the use of thermal solar energy and the woodchip heating. If the large-scale photovoltaic systems are also taken into account, this results in a positive energy balance of approximately 290 kWh/m² p.a. in terms of the energy gains – provided that the user electricity consumption is ignored (i.e. balanced within the limits of the EnEV). If the user electricity consumption is also included in the balancing, the positive energy characteristic is nevertheless still approximately 160 kWh/m² p.a.

Construction-based innovations
Timber-frame block of flats with high degree of prefabrication

In the central part of the project area, four- and seven-storey mixed-use buildings are being constructed north of the Moosbach river. A special feature of the buildings is that their load-bearing structure is made of timber. Particularly progressive is the high degree of prefabrication, which promises low construction costs in future. A four-storey building was completed at the end of April 2010. It took only four days to construct. In energy terms, the timber homes are equivalent to the KfW Efficiency Building 70, and with a few changes can also be constructed to the passive house standard.

Refurbishment: pre-fabricated timber elements with integrated surface heating

The use of externally applied timber facade elements with integrated thermal insulation and pre-installed new windows enables interventions within the flats to be reduced to a minimum during the refurbishment phase. It is also possible to integrate building services components within the external timber refurbishment elements that would otherwise have to be installed in the flats. A special feature of this technology is the necessity for precise measurements in order to enable the refurbishment elements to adapt to measurement deviations that always occur in existing structures. In the pilot project, a tacheometric process was utilised that enables rough surfaces to be very precisely mapped. Building 353 has already been refurbished with this technology, whereby partial use was made of surface heating systems that were installed on the inside of the insulation elements. For further applications, it is also being considered whether to install ventilation ducts and cable routing in the elements. Parallel to the development of the elements, studies conducted by the Rosenheim University of Applied Sciences using stationary observations demonstrated the functionality of the facade heating system. Non-stationary calculations with the WuFi Pro building component simulation program clearly showed that the inclusion of heating with heating temperatures of 25 °C can be beneficial during steady periodic conditions. The average surface temperatures were raised above the indoor air temperature, even if only by a small amount. If the energy deployed is generated by renewable means (e.g. via solar collectors), or if residue heat is recycled from other heating systems, the results of Rosenheim University of Applied Sciences show that the facade heating system can certainly be rated positively.

Realisation

The first work was already initiated during the design and planning phase. The refurbishment is completed in the hotel complex and sections of other buildings have already been refurbished or are currently undergoing refurbishment. Solar Network 1 in the northern part of the site, which is equipped with heat pumps in each building to heat water, has been in test operation since the summer of 2009. Eight buildings and the hotel complex are connected to it. The measurement data are continually logged and monitored online.

A balanced, zero fossil fuel energy target is still being aimed for in the North Network. In addition to improvements in the demand side, this is to be achieved by means of a woodchip boiler, extensive solar thermal collectors, a large-scale, ground-mounted photovoltaic system and a PV system on the roofs of the former aircraft hanger. Approximately 1,000 m² of solar thermal collectors are currently being installed. Fixed, 0.5 MWp roof-mounted and 2.4 MWp ground-mounted systems are planned for the photovoltaic systems. These are expected to generate around 3.0 GWh p.a.

Monitoring

Solar Network 1 in the northern part commenced operation in summer 2009. To measure and monitor the new building systems equipment, an Internet–based display system has been set up. An easily understandable, graphical view of the buildings in the North Network displays current weather data (outdoor temperature, air humidity, global radiation and wind strength) as well as the energy balances of the individual buildings (including heat consumption, solar yield and solar coverage) in real time.

Comprehensive monitoring is planned to check the energy-based performance of the overall project and to optimise the operation. For this purpose, the MoniSoft software, which has been specially tailored for monitoring purposes by the Department of Building Physics and Technical Building Services (fbta) at Karlsruhe University, commenced operation on a monitoring computer in the boiler house in the grounds of the park. This system directly captures building control data from measurement points and stores it in its database. Up to 1,500 measurement points have been defined for the overall site.

Energy characteristics

beforepotentialafterunit
Energy consumption: Gross floor area70.000,00  
Final energy requirement of typical residential buildings (according to EnEV 2007)351,00130,00 kWh/m²a
Primary energy requirement of typical residential buildings (according to EnEV 2007)459,00  kWh/m²a
Final energy requirement of typical commercial buildings (according to EnEV 2007)268,0089,00 kWh/m²a
Primary energy requirement of typical commercial buildings (according to EnEV 2007)351,00  kWh/m²a

Additional information:

Related topics

 
Project management, controlling
B&O-Wohnungswirtschaft Bad Aibling
Overall concept, project controlling
RK-Stuttgart Architekten und Ingenieure
Supply concept
GEF Ingenieur AG
Architecture, urban development
Schankula - Architekten / Diplomingenieure
Building services equipment, supply technology
B&O-Wohnungswirtschaft München, Chemnitz, Berlin
Energy technology, control, visualisation
Enwerk GmbH
Measurement data logging, data logging software
EA EnergieArchitektur GmbH
Evaluation
Hochschule Rosenheim
  • Aerial photo of the former American military base in Bad Aibling, July 2007
  • Hydraulically separation of the project area into a North and South Network
  • Urban development design, March 2008
  • Refurbished building in the new hotel complex
  • Planned wooden high-rise residential building
  • Initial state: Typical buildings on the former military base
  • Former accommodation before refurbishment
  • Initial state: Build-up of basement ceiling in building 355
  • Initial state: Survey of the roof insulation in building 303
  • Insulation measurement (Isofloc)
  • Refurbished building 356
  • Domestic hot water backup heating via decentralised heat pumps in the already refurbished hotel complex
  • Heating centre of the local heat supply system refurbished in the 1990s
  • Central heating boilers
  • Metering of heat flow rates in the heating centre
  • Modules of the planned wooden chip heating station
  • Container in front of the wooden chip heating station
  • To measure and monitor the new building systems equipment, an Internet–based display system has been set up.
  • Existing barrage of the Moosbach river