Buildings of highest energy-efficiency with integrated renewable energy development

For the future supply of energy services the combination of energy efficiency, energy storage and decentralized use of renewable energy in buildings offers itself. The project identified dynamic potentials of possible active and passive energy yields of construction units with use of renewable energy sources, pointed future solutions to energy-efficient and ecological design of building construction-units and united all results to a signpost: From today's passive house to the energy-plus-house of the future.

Short Description




Starting point and Motivation

Energy supply services for buildings (residential and non-residential) are largely responsible for the primary energy consumption in Austria. Because the supply is mainly based on fossil energy sources, high import dependence and a crucial security of energy supply are given. In addition, fossil energy sources cause immense greenhouse gas emissions during the production process of components and the building operation, briefly about the whole life cycle. From an ecological and an economic view, a sustainable and secure supply of renewable energy sources as well as energy-efficient system solutions shall be applied.

Contents and Objectives

The conception of energy-efficient components of the building envelope with integrated renewable "energy production" is the prior step and the starting point of the creation of a sustainable energy system with a clear rise of energy efficiency, reduction of greenhouse gas emissions and improvement of security of supply by the use of renewable energy sources.

The long-term vision is a building sector evolving from an energy consumer to a supplier of energy, which corresponds to the innovative concept of a plus-energy-building. The core question of this work thus treats the applicability and the benefits of plus-energy-buildings in terms of energy, ecological and economic feasibility, to design the entire building envelope optimally, so that heat losses are minimized and profits from the use of renewable energy can be maximized.


Shown by case studies (residence, office and factory buildings) it becomes evident, that plusenergy-buildings are economic feasible, as the technology is already available. Three important aspects in the design of plus-energy-buildings, which influence each other to some extent, are 

  • the location, 
  • the architecture and 
  • the choice of heating system, for which heat pumps, pellet boilers or district heating systems are probably the best solution. 

Knowledge of fundamental climatic data of the building site appears essential for high-quality planning. Photovoltaics can be used as an elementary component of a plus-energy-building. If photovoltaic technology and prices evolve as in the past few years, it will reach a widespread adoption in the building sector during the next decade very likely. Thus, both the energy efficiency and the corresponding integration of renewable energy sources in buildings are expected to play a significant role in terms of reducing greenhouse gases and a reduced dependence on fossil fuels.

The economic evaluation of the cases studies is conducted by the present value method. The best economic solution does not utilise the full ecological nor energetic potential of improvement. However, it achieves a negative non-renewable primary energy balance per year and a plus-energy standard by definition.


With regard to the future relevance of plus-energy-buildings, beside new buildings, there is a much greater potential in the existing building stock. So, it will be important to focus on solutions for plus-energy-buildings in the existing building stock. However, it will last some decades before plus-energy-buildings will impact significantly on the total building stock in Austria.

Depending on the diffusion rate - in the scenarios of low, medium and high technology diffusion - 5 to 21% of the Austrian housing stock will probably reach a plusenergy standard in 2050. Drivers towards a high diffusion of plus-energy-buildings are cost savings of the new technology, subsidies and regulatory policies (e.g. an ambitious implementation of the EU Buildings Directive 2010/31/EU).

Depending on the diffusion scenarios about 100,000 to 400,000 residential buildings could reach a plus-energy standard in 2050. In the non-residential building sector 8,000 to 50,000 plus-energy-buildings can be expected by 2050. With a total of around 2.1 million buildings in Austria in 2050 up to onefifth may reach a plus-energy standard.

Project Partners

Project management

Reinhard Haas
Vienna University of Technology, Institute of Power Systems and Energy Economics (Energy Economics Group)

Project or cooperation partner

  • Vienna University of Technology, Institute for Thermodynamics and Thermal Engineering
    Contact person: Markus Haider
  • Vienna University of Technology, Institute for Engineering and Technology
    Contact person: Thomas Bednar
  • Vienna University of Technology, Institut for Architecture and Design
    Contact person: Karin Stieldorf
  • GrAT - Center for Appropriate Technology (scientific association at the Vienna University of Technology)
    Contact person: Robert Wimmer

Contact Address

Vienna University of Technology, Institute of Power Systems and Energy Economics (Energy Economics Group)
Gußhausstraße 25-29/373-2
A-1040 Wien
Tel.: +43 (1) 58801-37352 (Reinhard Haas) or -37372 (Raphael Bointner)
Fax: +43 (1) 58801-37397