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Development of a Reference Scenario for the German building sector in respect of the overall aim "40% CO2-reduction until 2020"

BMVBS-Online-Publikation 26/12, Ed.: BMVBS, December 2012

Kjell Bettgenhäuser, Thomas Boermanns, Jan Grözinger
Federal Ministry of Transport, Building and Urban Development, Berlin
Alexander Renner

Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR), Bonn
Christian Ahrens


Research task and approach

Subject of this study is to develop a Reference Scenario for the German building stock for the overall aim of 40% CO2-emission reduction until 2020, based on 1990 values. The Reference Scenario quantifies the impact of policy measures in the building sector, which have been implemented until January 1st 2010. All buildings in the sectors households, trade and retail, services and transport are covered. Buildings in the industry sector are due to their high heterogeneity not within the scope. The investigation consists of the following two parts:

Chapter 1 comprises the ex-post evaluation of existing studies and analyzes the effects of policy measures from 1990 up to 2010.

In chapter 2 a scenario calculation for the years 2010 to 2020 is been done in order to forecast the future effects of the policy measures, which have been in force until January 1st 2010. Beside the main results sensitivity analysis are done concerning retrofit rates, increasing climate change and the impact of population development. The scenario calculation is done using the Ecofys Built-Environment-Analysis-Model BEAM². Main results are developments of conditioned floor areas, heating demand, end- and primary energy demand and CO2-emissions.

Afterwards the achievement of the aims is discussed, looking at the one hand at the CO2-emissions reductions from 1990 to 2020 and on the other hand at the heating demand reductions from 2008 to 2020. Apart from that suggestions for additional policy measures are formulated and further research issues are outlined.

Results of the ex-post evaluation

The following figure gives an historic overview on the end energy consumption in the German building sector. The values are form the "BMWi Energiedaten" (Federal Ministry of Economics and Technology) and show the development for heating, hot water and Lighting from 1990 to 2009.

The historic development of the CO2-emissions for the building sector cannot just be taken from a statistic (as the end energy consumption), because there is no sector-specific numbers available. Therefore the CO2-emissions for this study are calculated based on the end energy consumptions from "BMWi Energiedaten", taking into account the split of the energy carriers and emissions factors. The CO2-emissions are not shown explicitly here, but are part of the figures for the ex-ante evaluation.

Historic overview on energy consumptions for heating, hot water and lighting in the sectors private households, trade and retails, services and transport.Historic overview on energy consumptions for heating, hot water and lighting in the sectors private households, trade and retails, services and transport. Source: BMWi Energiedaten

The effects of the following packages of measures are given separately. It's distinguished, whether a measure is covered by the Integrated Energy and Climate Program (IEKP) of the German Government. The following measures are part of the Program:

The "Energy Saving Ordinance", the "KfW Building Retrofit Program", the program "Modernization of Social Infrastructure", the "Renewable Energy Heat Law", the program "Retrofit of Federal Buildings" as well as the "Market Stimulation Program" for renewable energy technologies and the "Replacement of electrical heating systems".

Furthermore the following policy measures are addressed, which are not part of the IEKP:

The KfW program "Energy Efficient New Buildings", the program to support "Social Housing", the "Energy Performance Certificate" and the "On-Site Energy Advice" as well as the program "Urban Restructuring in Eastern Germany".
The quantification of all measures is shown in table Tabelle 24.

Results of the Ex-ante-Analysis

The calculations for the reference scenario for the period 2010 to 2020 are done with the Built-Environment-Analysis-Model BEAM². A description of the model can be found in section 1.5. After having defined representative reference buildings for both residential and non-residential buildings, input data like heated floor areas, energy standards, mixes of energy carriers, retrofit and new building standards as well as the heating degree days are explained in further detail.

The following packages of policy measures are quantified: "KfW Building Retrofit Program", "Renewable Energy Heat Law", "Market Stimulation Program" for renewable energy technologies and the KfW program "Energy Efficient New Buildings". The reminding effects, which are not part of these packages, are assigned to the measure "Energy Saving Ordinance".

The main results of the study are the historic development and the forecast of CO2-emissions until 2020. In the following they are shown together with the sensitivity analysis.

Sensitivity for Retrofit Rates
The retrofit rate is assumed with 1.4% per year. Due to the fact that it's not result of a statistical survey, but is set together out of different partial surveys and indicators, it's subject of a specific uncertainty. Therefore a sensitivity range of +/- 0.4% has been set to cover the bandwidth of the existing numbers in literature, resulting in 1.0% and 1.8% per year.
The impact on the CO2-emissions for the sensitivities is shown in the following figures.

CO2-Emissions for different retrofit rates, years 1990-2020CO2-Emissions for different retrofit rates, years 1990-2020

CO2-Emissions for different retrofit rates, years 2010-2020CO2-Emissions for different retrofit rates, years 2010-2020

As shown in the figures, the retrofit rate is an important input for scenario calculation. The lower rate of 1.0% per year leads to clearly missing the target, while the target is achieved for the higher rate of 1.8% per year. It`s to bear in mind, that increasing the retrofit rate from 1.4% to 1.8% means approx. 30% increase in activities.

Sensitivity of ongoing Climate Change
The sensitivity of ongoing climate change is been calculated using data from a recent study of Germany's National Meteorological Service [DWD2010], showing the future impact of climate change in a scenario for 2035.
The impact from the sensitivity analysis on the CO2-emissions is shown in the following figure.

CO2-Emissions for future climate changeCO2-Emissions for future climate change

The results show as expected, that climate change and a warmer climate lowers the energy demand and therefore CO2-emissions for heating purposes, which leads to a better chance to reach the target in 2020. On the other side it is expected, that lower heating demands are overcompensated by increasing cooling demands for buildings, which are usually supplied by electricity and therefore have negative effect on the CO2-emissions. While general cooling demands for non-residential buildings are taken into account at the auxiliary energy demands, the increasing effect for ongoing climate change has not been considered.

Sensitivity of constant population development
Apart from climate change and retrofit rates, the future population and floor-space development has major impact on the energy demand for buildings. The parameters are the new building and demolition rate. Therefore a scenario is calculated, where the new building rate is set to the demolition rate and therefore overall floor area remains constant.
The impact of a constant floor area development with respect to CO2-emissions is shown in the following figure.

CO2-Emissions for constant floor areas (new building rate = demolition rate)CO2-Emissions for constant floor areas (new building rate = demolition rate)

A constant floor area development shows as expected a stronger decreasing energy demand and emission path, which will most probably lead to an achievement of the targets.

To achieve the target with respect to the CO2-emissions (-40% related to 1990 level), a maximum of 135,700 kt CO2 in 2020 (overall emissions, including district heat and electricity) can be emitted. The reference scenario calculation with BEAM² results at approx. 138,000 kt CO2 in 2020.
During the years 2010-2020, 27,700 kt CO2 needs to be conserved according to the target, while the reference scenario comes up with 25,600 kt CO2 (approx. 90% of the remaining gap from 2010-2020.

The abstract is part of the German publication "Entwicklung eines Referenzszenarios im Gebäudebereich für das Gesamtziel 40% CO2-Einsparung bis 2020" - BMVBS-Online-Publikation 26/12, Hrsg.: BMVBS, December 2012, Berlin