Ludwigsburg - Grünbühl

Grunbuhl

Specification sheet

  • Number of buildings: 160
  • Total heated area (%residential): 77.000 m² (90%)
  • Age of the district: built just after World War II
  • Energy state: most of the building stock still in the original state
  • Actual heat supply: gas boilers
  • 3D city model: CityGML LoD1 and LoD2
  • Calculated heating demand: 106 kWh/m².yr

History of the district

The construction of the district Grünbühl took place at the end of the World War II to address the urgent lack of living accomodations.
In the 1980's, another important construction phase was undertaken, including the construction of many multi-family houses and a high tower building: the so-called "elephant". refurbishment rate in Grünbühl

The majority of the building stock is still in the original state, in particular the original first barracks. Since 1990, around 1% of the total living area has been refurbished per year (780 m²).



3D city model and Data collection

A CityGML 3D city model Level of Detail 1 and 2 has been generated for the project Klimaneutrale Kommune - Ludwigsburg.

To semantically enhance this 3D city modell, the City Ludwigsburg supplied us with CENSUS-Data (e.g. number of storeys, building age class, building usage, building type, ownership, number of appartments, DHW facilities per appartment, Heat installation), as well as year of refurbishment of the buildings owned by housing companies.
Grunbuhl - Facade damages Further information data have been collected during an on-site survey (window to wall ratio, outside insulation thickness, window types, lived/unlived attic storey and cellar, facade damages).
U-values and other building physics parameters have been estimated, using the "Deutsche Gebäudetypologie" of Institut Wohnen und Umwelt.

Finally, the Stadtwerke Ludwigsburg (energy supply company of Ludwigsburg) supplied us with gas consumption data per building block, to assist in the validation of the simulation results with the actual consumptions.

Results

The simulated heating demand per building in Grünbühl varies from 30 kWh/m².yr for fully refurbished buildings in 2007, up to almost 200 kWh/m².yr for post-war building blocks in poor condition (e.g. cracked walls, humidity damage, non-airtight roofs and windows).
The mean heating demand in this residential post-war district reaches 106 kWh/m².yr.
visualisation heating demand Ludwigsburg
To evaluate the accuracy of the model, simulated and real yearly heating demands were compared per building block and for the whole district. The mean deviation between the simulated and real heating demands for the whole district reached 18%.

>> further information in the paper 3d-Stadtmodelle für die Wärmebedarfberechnung.




Karlsruhe - Rintheim

Karlsruhe

Specification sheet

  • Number of buildings: 30
  • Total heated area (%residential): 65.000 m² (100%)
  • Age of the district: built in the mid 50's and early 70's
  • Energy state: 1/3 fully refurbished
  • Actual heat supply: mainly gas boilers
  • 3D city model: CityGML LoD2
  • Calculated heating deman: 91 kWh/m².yr

History of the district

In the residential district "Rintheimer Feld", the public housing society Volkswohnung GmbH Karlsruhe owns 30 buildings, with a total living area of 65.000 m².
The buildings were built in two phases: 22 multi-family houses in the middle 1950's and eight tower buildings in the early 1970's.

Between 1998 and 2008, 11 buildings were fully refurbished, the remaining 2/3 are either only partially or non-refurbished.


3D city model and Data collection

A few years ago, a detailed energy audit of the building stock was carried out. The buildings were classified into six different types according to their energy efficiency:

  • Type 1: non-refurbished multi-family houses, built in 1954-1956
  • Type 2: non-refurbished tower buildings, built in 1974
  • Type 3: multi-family houses, built in 1974, partially refurbished (façade in 1975, roof in 2003)
  • Type 4: multi-family houses, built in 1954, fully refurbished in 1998
  • Type 5: multi-family houses, built in 1954, fully refurbished in 2000
  • Type 6: multi-family houses and tower buildings, fully refurbished in 2007
6 building types of Karlsruhe-Rintheim

The detailed information collected during this audit (e.g. U-values assessment, thermal bridges, heating system) was integrated in the 3D city model Level of Detail 2 of the city Karlsruhe as building semantic information.


Results

heating demand comparison

The mean heating demand per building type vary from 35 kWh/m².yr for buildings fully refurbished in 2007 (Type 6) up to 158 kWh/m².yr for non-refurbished buildings from the 50's.

The mean deviation between the simulated and real district heating demand reaches +6.7%.

In the building type 1, single room gas furnaces supply heating, individually controlled by the tenants. This may explain the relatively low consumption observed in this building category, in which tenants might adopt energy conservation behaviour in order to lower their energy bills.




Rotterdam - Bospolder

Rotterdam

Specification sheet

  • Number of building addresses: 3729
  • Total heated area (%residential): 300.000 m² (68%)
  • Age of the district: built between 1910 and present date
  • Energy state: very heterogeneous
  • Actual heat supply: mainly gas boilers
  • 3D city model: CityGML LoD2
  • Calculated heating demand: 132 kWh/m².yr
  • Calculated potential heating energy savings: 59%

History of the district

The district Bospolder was built originally in the 1910's, west of the city Rotterdam.
Since 1990 to present date, a new building wave has added half of the actual living area, as well as commercial and office buildings.


3D city model and Data collection

The Municipality of Rotterdam has been using a virtual 3D city model LoD2 of the whole city since the early 2000's.
Thus far, the aim of this 3D city model has been pure visualization, so that the numerous typological and geometrical (unvisible) errors of the model have gone largely unnoticed.
Such errors are not compatible with 3D city model based energy analysis which requires a high quality city model.

The first step of the process was to signicantly improve the quality of the model, first with automatic corrections thanks the healing module CityDoctor, and then using manual repair for the remaining errors (missing surfaces etc.)
Even after this healing phase, 50 invalid building blocks remained not-exploitable for the energy analysis, having either no volume, or too many missing surfaces.

In parallel to this 3D city model, the City of Rotterdam supervised huge databanks containing datasets organized per building addresses (e.g. building year, main and secondary usage, number of storeys, neighbourhood name) as well as per dwelling (e.g. living area, ownership, dwelling type, energy label) for the whole city Rotterdam.
The second step of the process was to connect these datasets to the virtual building models, and then to integrate the relevant semantic information data into the virtual 3D city model.
Unfortunately, no information about the refurbishment state of the buildings was available, which may have led to significant deviations in the simulation results .

Because no local/national building typology library presented precise enough U-values and further thermal building parameters per building class, the "Deutsche Gebäudetypologie" of the Institut Wohnen und Umwelt was used.

Results

Heating demand and CO2 emissions per m² floor area were calculated.
A refurbishment scenario, defined according to the recommended refurbishment measures of the Institut Wohnen und Umwelt, was also simulated. The relative heat energy savings were then calculated. visualisation heating demand Rotterdam
visualisation CO2 emissions Rotterdam
visualisation heat energy savings Rotterdam