LZE 100 Lighthouse Objects - Long-term evaluation of the energy consumption of 100 energy-efficient buildings in Austria as a representative cross-section of Austrian lighthouse objects

Collection, evaluation and analysis of energy consumption data from 100 energy-efficient buildings in Austria over an operating time of 3 to 25 years as a representative cross-section of Austrian lighthouse objects. Differentiation according to building types, energy sources and determination of real greenhouse gas emissions. Comparison of the measured consumption to benchmark values.

Short Description

Motivation and research question

Austria has a long tradition of constructing highly efficient buildings - both in the context of scientifically supported research projects and without scientific support. Many research and model projects show that very low consumption and greenhouse gas emissions can also be achieved in practice and that real consumption can be well predicted with suitable calculation tools using realistic boundary conditions of use. Nevertheless, it is often postulated that the real consumption of high-efficiency buildings is significantly higher than the energy demand values calculated in advance.

The main research questions are:

  • What are the real consumptions of high-efficiency buildings of different use categories?
  • How high are the savings potentials compared to conventional new buildings, refurbishments and existing buildings of the same use category?
  • How high are the greenhouse gas emissions, calculated from real consumption?
  • How can the greenhouse gas emissions be calculated realistically?

The project can also serve to provide a basis for answering the following questions:

  • What realistic contribution can buildings make to reduce final energy consumption, decarbonisation, and reducing energy import dependence?
  • Which concepts for constructing highly efficient buildings have proven themselves in practice?
  • What are the necessary next steps in the building sector?

Initial situation/status quo

As a basis for the analysis of reduction potentials, the status quo of final energy consumption for space heating and hot water of multi-family buildings is presented below as an example. The analysis is based on consumption data evaluations for the largest possible building stock. The total building stock requires on average a specific final energy consumption for space heating and hot water between 105 kWh/(m²WNFa) for buildings supplied with district heating and about 140 kWh/(m²WNFa) for oil and gas heated buildings. The specific final energy consumption for space heating and hot water of typical new multi-apartment buildings averages about 85 kWh/(m²WNFa).

Project contents and objectives

The project at hand aims at collecting consumption values of highly efficient buildings, evaluating them statistically and comparing them with the consumption of similar building types in a "usual" energy level in order to enable an objective discussion based on facts. This comparison is intended to highlight potential savings that are not based on theoretical calculations but on measured consumption.

Based on the energy consumption data, the real greenhouse gas emissions of the buildings in operation are determined. The medium-term trends in the development of specific emissions of the energy carrier electricity are also taken into account.

The presentation and discussion of the results are to be elaborated taking into account the historical development of technologies used or technological innovations in Austria, and deriving from this the need for further development and research.

Methodological approach

To answer the main research questions, the energy consumption data of more than 100 energy-efficient best-practice buildings in Austria will be collected and analysed over an operating period of 3 to 25 years. The collection and analysis is done in different depths and temporal resolutions depending on data availability - for scientifically supported projects very detailed, for other projects on the level of measured and billed annual final energy consumption for heating and hot water as well as for other energy applications.

Results and conclusions

The evaluation of the energy consumption data of the investigated, innovative multi-apartment buildings results in mean, specific final energy consumptions for heating and hot water of about 64 kWh/(m²WNFa) for the energy carriers gas and district heating and about 16.5 kWh/(m²WNFa) for the energy carrier electricity (heat pump). The average specific final energy consumption for heating and hot water of the evaluated multi-apartment buildings is thus about 25% below the consumption of typical multi-apartment buildings.

The best gas-heated multi-residential buildings achieve specific final energy consumptions for heating and hot water of 42 to 44 kWh/(m²WNFa). The best district-heated multifamily buildings achieve specific final energy consumptions for heating and hot water of 50 to 53 kWh/(m²WNFa). The consumption of the best projects is thus up to 50% below the consumption of typical multi-apartment buildings. The best five heat pump-heated multi-residential buildings - including one building renovation - achieve specific final energy consumptions for heating and hot water of 12 to 13 kWh/(m²WNFa).

The CO2eq emissions of the natural gas-heated buildings in the sum of all energy applications are several times higher than the Paris-compatible emissions (3 to 6 kg/(m²WNFa)). Gas-heated buildings cannot meet the emission limits required for climate protection reasons.
Emissions from the best heat pump-heated multifamily buildings are about 11 kg/(m²WNFa) with the current electricity mix. With specific greenhouse gas emissions from consumer electricity expected in 2030, the best heat pump-heated buildings will achieve emissions in the Paris-compatible range (i.e. up to a maximum of 6 kg/(m²WNFa). Similar results are obtained for the best district-heated buildings as well as for renovations and non-residential buildings.

The following main findings emerge from the project.

  • Finding 1: High-efficiency buildings work in practice.
  • Finding 2: High efficiency can be planned
  • Finding 3: High efficiency is economical
  • Finding 4: The current minimum requirement level is not compatible with the Paris target
  • Finding 5: Paris-compatible energy sources for new construction - heat pump or local/district heating
  • Finding 6: Large PV systems are close to economic viability
  • Finding 7: Analysis of real energy consumption of buildings is still in its infancy


The project shows that Paris-compatible levels can already be achieved with components and concepts that have been commercially available for most of the last 20 years. Reducing the energy demand and greenhouse gas emissions of the building sector is primarily an implementation problem - the necessary technologies are known and available. The following recommendations for implementation measures emerge from the project.

  • Recommendation 1: Immediate ban on fossil fuels in new buildings.
  • Recommendation 2: Binding timetable for phasing out fossil fuels in existing buildings
  • Recommendation 3: Increase the requirement level for the building envelope in new construction and refurbishment
  • Recommendation 4: Shift subsidies from new construction to refurbishment and focus on Paris-compatible qualities

The following recommendations for further research and development emerge from the project.

  • Start-up funding for serial refurbishments of high-energy quality.
  • Development of methods for analysing the energy quality of large building stocks based on consumption evaluations
  • Development and test of funding models based on real energy consumption

Project Partners

Project management

LANG consulting – Ing. Günter Lang

Project or cooperation partners

Energieinstitut Vorarlberg

Contact Address

LANG consulting
Ing. Günter Lang
Linzerstraße 280
A-1140 Wien
Tel.: +43 (650) 900 20 40
E-Mail: g.lang@langconsulting.at
Web: www.langconsulting.at und www.energieinstitut.at