Foto: Frontansicht des Biohofs Achleitner

OEKOPLUS-KOMPLEX - Analysis of the technical, economical and ecological preconditions for the establishment and utilisation of plus-energy-buildings and building assemblies

The evolution of the low energy house and the passive house standards to the plus energy standard results in a clear reduction of green house gas emissions as well as the primary energy input. The goal of the project was the determination of the technical, ecological and economic basic conditions for the construction and the use of "plus-energy-buildings" in order to finally realize them.

Short Description




Starting point/Motivation

The construction and operation of buildings contributes significantly to the Austrian greenhouse gas emissions (GHG-emissions) and energy consumption. In the recent years so-called “plus-energy-buildings” were developed and first demonstration buildings installed, to reduce GHG-emissions and energy consumption in the building sector. In general the term “plus-energy-buildings” is used for buildings which generate more electricity than is needed by its resident within one year. However, there is no commonly accepted definition of “plusenergy-buildings”. Therefore in this project the term refers to buildings, which reach at least zero GHG-emissions over the total life-cycle of the building (including construction, operation, and demolition), due to the compensation of GHG-emissions with surplus energy.

Expressed more accurately this buildings are called “climate-neutral-buildings”. If climate neutral buildings are possible, and which technical, environmental and economic requirements are necessary for such buildings, was investigated in this project.

The project team consisted of JOANNEUM RESEARCH Forschungsgesellschaft mbH, Sauper Umweltdatentechnik GmbH, KLH Massivholz GmbH, Softtechenergy PlanungsgmbH, and Herbert Pexider GmbH. Additional partners from architecture and research cooperated with the project team and provided data and know how in the field of energy efficient and future buildings.

Content and Objective

Content of the project was the investigation of the possibilities to reach “plus-energybuilidings”, with real existing buildings as starting point. In the first step GHG-emissions and non-renewable primary energy demand for construction, operation and demolition of the buildings was determined. Subsequently all relevant technologies for energy production on the building surface and within the building were collected. For the most promising technologies combinations of buildings and “technology options” were investigated. For selected combinations a technical, environmental and economic assessment was performed.

Goal of the project was to determine the technical, environmental and economic requirements of the construction and operation of plus-energy-buildings on the basis of existing buildings.


Results are the GHG-emissions and non-renewable primary energy demand of the investigated buildings for the actual condition, identification of relevant technologies for plusenergy-buildings (technology options), an electrical energy balance for different technology options, and the environmental and economic assessment of buildings and technology options.

Starting point for the assessment was the selection of six existing buildings: three single family homes, one multi-story building, an event-building, and a housing complex. The investigation of GHG-emissions and the non-renewable primary energy demand for the actual condition showed:

In the construction phase of the investigated buildings the potential to reduce GHG-emissions and non-renewable primary energy demand is rather low. Nevertheless, using insulation material with low GHG-emissions and low mass (amongst others by using “light” construction material e.g. “hollow concrete construction”) GHG-emissions can be reduced.

The operation phase of the building has a significant influence on the GHG-emissions and the non-renewable primary energy consumption. A low energy demand of the building, minimizing the use of fossil energy carriers and maximizing the use of renewable energy carriers leads to a significant reduction of GHG-emissions during the operation phase.

Relevant technologies for heat and electricity production with renewable energy carriers in plus-energy-buildings are:

  • photovoltaic (PV)
  • small wind turbines
  • small hydro power plants
  • heat generation and combined heat and power generation with biomass
  • solar thermal heat plants
  • heat pumps

All these technologies, with the exception of small hydro power plants (due to the site specific and limited usage options), were examined more closely.

For the combinations of technology options and buildings, which resulted in a “plus-energyproduction”, an environmental assessment was performed. The development of GHG-emissions and non-renewable primary energy demand for the total building life-cycle (construction, operation, demolition) was estimated. The economic assessment was performed for two buildings in combination with technology options, which lead to climate neutrality. Economic aspects of electricity and heat production were investigated and the additional investment costs for plus-energy-buildings estimated.

Based on the results of the technical, environmental and economic evaluation, the following conclusions are drawn:

  • Suitable technologies for electric energy generation are photovoltaic and small wind turbines. Photovoltaic plants have a high building surface area demand, which is a disadvantage for multi-story buildings. The energy output of small wind turbines is strongly site specific. A detailed technical and economic planning based on the geographic and legal framework is necessary.
  • Electric “plus-energy-production” is for all investigated buildings possible. In the planning phase, however, optimizing the system design and minimizing the energy demand is important.
  • Suitable technologies for thermal electricity generation are heat pumps, pellet boiler and solar thermal plants. Pellet boilers show an advantage for electric “plus-energyproduction” due to the significant lower electricity consumption compared to the heat pump. Solar thermal plants are in competition for buildings surface space with photovoltaic plants.
  • The environmental assessment showed that climate-neutral-buildings are possible. The investigated technology options are environmental optimized alternatives, which demonstrated the maximum GHG-reduction potential.
  • The results of the environmental assessment are strongly influenced by assumptions, which are basic for the assessment (e.g. are GHG-emissions investigated or the primary energy demand, which energy carrier is substituted by the surplus electricity of the buildings).
  • The building site is crucial for the mobility behavior of the residents. If the GHG-emissions for transport are included in the assessment, none of the investigated buildings reaches the status of a “climate-neutral-building”.
  • Photovoltaic plants have high investment costs (additional costs of minimum 20% of the building construction costs). The profitability depends on the feed-in tariff, the orientation of the panels and the financing structure (high capital costs for external financing).
  • From an economic point of view small wind turbines do not make sense for the investigated sites (due to low energy output and high investment costs). The feed-in tariff is too low to compensate the high electricity production costs.
  • The additional investment costs for the construction of a climate-neutral-building compared to a low-energy-building are at least 20% of the construction costs.

Prospects / Suggestions for future research

A pre-condition for the successful operation of a plus-energy-building or a climate-neutralbuilding is to be interested in the technical plants and to take responsibility as a supplier of electricity. For the market implementation of such buildings it is recommend to further work on the following task:

  • Role of plus-energy-buildings in smart-city-concepts ? Development of tools for simple mapping of GHG-emissions and primary energy consumption for the total building life-cycle.
  • Integration of plus-energy-buildings as electricity suppliers and consumers in existing and future power grids (smart grid); investigation of the influence on the power system and role of electric energy storages in this context.
  • Additional investigations on the mobility behavior of the residents and the impact on land use planning and regional development.
  • Possibilities to design housing complexes and multi-story-buildings as climateneutral-buildings.
  • Additional possibilities to reduce the electricity consumption in buildings (e.g. usage of low-tec facilities and non-electric building equipment)
  • Installation of a working group for plus-energy-buildings and climate-neutral-buildings and integration in already existing networks and initiatives (e.g. IG Passivhaus, klima:aktiv).

Project Partners

Project management

DI (FH) Stefan Gunczy
Joanneum Research Forschungsgesellschaft mbH

Project collaborator

Karl-Peter Felberbauer, Johanna Pucker, Rudolf Stiglbrunner, David Tudiwer
Joanneum Research Forschungsgesellschaft mbH

Projekt- und Kooperationspartner

Contact Address

Joanneum Research Forschungsgesellschaft mbH
DI (FH) Stefan Gunczy
Elisabethstraße 5, 8010 Graz
Tel.: +43 (316) 876-1318
Fax: +43 (316) 8769-1338

Diese Seite auf Deutsch

Share this page ...

to Start