Requirements for energy-efficient and carbon neutral districts (EQ)
Werkstatt: Praxis Issue 81, Ed.: BMVBS, Berlin 2013
Project management BBSR:
The design of the ExWoSt study
The objective of the Experimental Housing and Urban Development Study (ExWoSt) was to examine the energy concepts in the districts of five cities and communities and on this basis to develop a measurement and collection methodology that enables a quantification of the energy demand and/or energy consumption on the analysis level of the district, thereby falling back on experiences from the evaluation level of the buildings and city / region. The calculation methodology has been compiled in parallel as an Excel workbook and tested in communal practice. For this, two additional so-called pilot districts were selected in addition to the other five model districts already participating.
The integration of mobility in energy concepts was given particular attention in the study. Currently, this usually only plays a secondary role in energy concepts and scientific observations on the subject of energy and districts. The variety of possible case constellations in regard to the housing market, building typology and owner structure substantiates the research approach via numerous model projects with respectively differing starting situations. In addition, the task of the study was to assess the state of energetic urban regeneration in the communities and on this basis draw conclusions for the suitability and layout of the control tool “energetic district concept“.
The study begins with the answer to the question of which district definition represents an appropriate analysis level, also in regard to communal usage (Chapter 2.1). Structure-typical limitations are widespread here in previous urban development funding. Against the backdrop of energy related questions another network structure potentially appears (district heating) the catchment area of which plays a role. Fundamentally however, the study recommends falling back on reliable demarcation models (building and social structure) and, if necessary, modifying the encompassing layout later based on energy-related and/or trafficoriented requirements or based on aspects that stem from the concept of the district as a sphere of activity.
The energy and climate protection question fundamentally requires the bundling of strategies to reduce resource consumption, save energy through technology and user conduct in order to increase energy efficiency and the usage of regenerative energies. This also applies to the district level (Chapter 2). A variety of measures is possible here both in the area of buildings as well as traffic. However, the relation to the district is evident to a varying degree with varying measures. The energetic renovation of buildings is for example, first and foremost influenced by the availability of technologies, their profitability and the decision of each owner – the relation to the district is rather indirect. In the case of heat grids the relation to the district is direct. District concepts thereby achieve an additional effect particularly in the two following areas:
- A concrete strategy aligned with the building and owner structure makes it possible to choose efficient approaches, including heat grids of diverse sizes. This especially concerns areas in which potentials, for example, are limited by building insulation. The limited spatial wrap-around also enables zoning legal regulations that are sensible, which would not have been generally as possible. For this strategy development the promotion of concept creation is in the KfW’s program “Energetic Urban Regeneration“ (KfW – Credit Institute for Reconstruction).
- The regeneration of whole districts enables synergies between the participants and opens a publicly effective perceivable window of time in which the individual owners as well as the owners of the buildings can learn about the whole regeneration process as well as about individual neighbours, overcome obstacles and be additionally motivated. In the KfW funding program the Regeneration Manager is in charge of this networking.
However the questions of building renovation versus social compatibility, insulation versus building culture and increasing building efficiency versus heat flux density provides potential for conflict. In this study the relativity of measures to the district is evaluated. The main result here is that there is fu rther need for research, especially in the analysis of the effects of economicand legal control tools. Only with this empirical foundation can a model of the energy consumption in the evaluation methodology be portrayed in a substantiated way.
The function of balancing on the district level is to make a comparative assessment of measures and development scenarios on a district level. In the meantime, several approaches with different objectives and levels of detail exist with the featured reference tools EFES from Austria, ECORegion, Energetic Plausability Check, GemEB Tool and the EnEff: Stadt District Balancing Tool. The differences in model configuration and purpose show that there cannot be one single model that is sufficiently precise for all questions and simultaneously easy to use. The way out of this dilemma in the study at hand was to develop a rough model that can be expanded depending on the presence of data and concrete questions.
Calculating energy and CO2
On this basis Chapter 3 depicts the work steps of energetic district balancing on the abstract level. The following fundamental position of points are deemed conducive to reaching the objective for the calculation methodology here :
- Traffic and building (with their upstream supply chain) are first modelled separately from each other and added together later on the level of the consumption of energy sources.
- A rough model enables the fast generating of some few results that can then be increasingly supplemented by the complex components.
- In general the “polluter-pays principle“ applies in the balancing.
- The model enables the calculation of potentials (setting aside the timeframe) and the modelling of scenarios in a more short-term timeframe by 2020.
- Energy demand and energy consumption have their respective advantages and disadvantages and will be set in where appropriate.
The diverse data sources can be categorised based on the first step – the opening balance at the current time. Here object-related surveys, samplings and district-specific measurements compete with district typologies or rather statistical data that has been gained on a higher spacial level. In practice there should always be a mix. Especially in the area of traffic local field research is often unavailable so work with district typologies is logical here. The study itself develops this. In the area of buildings the work with the IWU building typology is, for example, conducive for achieving the objective. The prognosis of district-specific unchangeable basis developments and the actual effects of districtrelated measures constitute Step 2 and 3 of the model. In conclusion the effects of CO2 in grams (g) is summarised. At the end of the chapter the own balancing methodology is introduced, which is documented in parallel in the compiled Excel workbook.
The calculation model is structured primarily in one part, which generates energy and CO2 balances based on the energy consumption on the district level taking the upstream chain into consideration. This is based on the consumption data from the previous years. On this basis a prognosis tool is established as a forward projection of the preceding balance up to 2020, with which individually selected scenarios can be portrayed for future developments. In the subordinate level the modelling of subareas building and traffic takes place taking the user into account.
The building model on file uses buildingspecific and individual data to be collected on the building level. Since a survey of all buildings in the district (especially the calculation of energy demand in the current state) represents a partially significant expenditure, the model is set up to be able to process individual questions even when the building list is only partially filled in (geometry data, building type, grid-bound energy sources, no building-specific demands or consumptions). Thus the compilation of a start balance is possible by entering the total consumption of grid-bound energy sources
on the district level and savings potentials and scenarios can be calculated with ease.
Because of the insufficient availability of district-related data on traffic volume and mobility behaviour the model in the area of traffic works with mobility parameters from the Germany-wide survey “Mobilität in Deutschland“ (MID – Mobility in Germany) 2008, which are differentiated with the help of a typology of different spatial structures. With the introduced balancing methodology a basic structure for district balancing is available to communities and their consultants so that not every community has to start from the beginning. But it does not replace detail calculations of special questions on location. Also in regard to the modelling, numerous further developments can be the object of further research.
7 model districts
With the model districts Leipzig-Connewitz, Marburg-Nordstadt, Rosenheim-Finsterwalder Straße, Stade-Hahle and Weißenfels- Alte Sparkasse as well as the newly incorporated pilot districts Sömmerda-Gartenberg and Naumburg-Südöstliche Altstadt, seven districts are examined in Chapter 4, which already have experience with work on the district level in other institutional contexts.Districts with private ownership were deliberately selected here as opposed to major housing developments that have already been developed extensively. However, the districts represent diverse
constellations of building age emphasis and housing market types. The process of district selection shows hereby that districts close to the inner city with partially historical building structures and a large percentage of non-residential buildings (Marburg, Weißenfels, Naumburg, with some exceptions Leipzig) as well as diverse structure types of the housing district of the 20th century, represent
the relevant structures with challenges in energetic city regeneration.
The latter range from garden cities (Sömmerda-Gartenberg) to urban expansions in post-war times with multi-storey residential construction, multi-family units and compact single family houses (Stade-Hahle, Rosenheim-Finsterwalder Au / Aichergelände). The amount of building age classes in the German inventory of buildings is high. The districts show, among others, that the communities have recognised the challenges of energetic city regeneration, see the special problems when addressing individual owners and in part already have at their disposal approaches to balancing districts.
The abstract is part of the German publication "Anforderungen an energieeffiziente und klimaneutrale Quartiere (EQ)", Werkstatt: Praxis, Heft 81, Hrsg.: BMVBS, Berlin 2013.