Objectives and target audience
Energy.
- Dwellings are constructed for high-energy efficiency having a winter garden and high insulation.
- Heating natural gas.
- Solar energy covers 50 to 70% of the needs for water heating.
- Maximizing energy efficiency.
- Heat consumption for the different units is between 50 and 64 kWh/m2a (measured).
Indoor Air Quality.
- Choice of materials and healthy without toxic emissions.
- For lighting the dwelling make use of natural sunlight.
- In the buildings electromagnetic fields were avoided.
Materials.
- Brick walls for privacy surround individual L-shaped houses with yards of approximately 150–200 m2. The drawing rooms and bedrooms face Southeast to Southwest. The other rooms function as insulating buffer zones to the north.
- The external structural components are highly insulated (taking into account the planning period early 1980s).
- Recovery of wood from cutting trees for furniture and interior architecture.
- Wood from local forests.
Waste management.
- Waste is separated better then demanded by regulation; glass, metal, textile, paper, plastic, and compost are separate fractions.
Water.
The use of rainwater and on-site wastewater treatment was an innovative breakthrough for
settlements in Austria. It was based on the principles of optimal conservation of drinking water and reducing water pollution. The result is an average drinking water consumption of
52 litres per person per day (compared to an average of about 150 l/pd).
- Rainwater is collected in 2.5 – 3 m3 underground cisterns for the single-family houses and an 86 m3 cistern for the apartment house.
- 10 dwellings are fitted with composting toilet (3 m3) situated in the cellars, saving 40 – 70
m3 of drinking water per unit per year.
- The community operates an organic sewage treatment system, which is laid out for a population equivalent of 90. Construction and function is based on the method of K. Seidel (1960). It consists of 3 single treatment pools and a cleaning pond with flow –form cascades. The purified water is used by a local market garden. The surplus water is sprayed over nearby fields
- The local precipitation on the 155m² – roof surface per home is enough for 6,6m³ water per month, enough for the laundry and the toilets. In spite of the Austrian rules that forbid the use of rainwater as shower water on hygienic grounds, there are two households that shower with the rainwater at their own risk.

Financial Resources and Partners involved
In the total construction costs of 4,170,000 Euro an amount of 470,000 Euro was invested in research.
Financing of the project:-
- Operating costs are funded by residents,
- The costs of construction were financed by both residents and through a loan payable over 25 years by the region of Lower Austria,
- The Austrian government has also assisted the project for environmental (tax credit for construction).

Process
It is an important example of attempts in the 1980s to integrate innovative ecological and social issues. Basis for these kinds of settlements were occupant health, productivity, social well being, and care for the environment. From the start 11 courtyard houses and 15 apartments, a nursery school, an office, vegetable gardens and an organic sewage treatment system were part of the settlement. In the beginning, it was planned to expand the village with additional 50 dwelling units, a reference and information centre for ecological farming and a Montessori school.

Results
Some green building concepts that did not exist before, such as the use of rainwater, the biological treatment of wastewater or pit toilets (or compost toilets), were allowed.
- As measured, the consumption of heat for different units ranges from 50 to 64 kWh/m2 per year.
- The consumption of drinking water average is 52 litres per person / day (vs. an average typically 150 litres / person / day): a reduction related to the use of compost toilets in most homes and the use of rainwater for toilet flushing, washing machines and watering gardens.
- A significant reduction of waste and sorting (organic waste, paper, plastic, metal, glass).
- 50% reduction in energy consumption.
- Using a system of biological treatment of wastewater.

Critical Success Factors / Challenges

Many problems, ranging from establishing democratic decision making to managing finances … had to be mastered by the prospective inhabitants. Two years after having moved into their homes, almost all residents declared that they could not imagine any other form of residency. It became clear through lengthy interviews that the social project Eco-Homes Gärtnerhof began only after building construction had been completed. The more than 40 children of this community are growing up in a world strikingly different from a typical urban environment. For them, perhaps, the Eco-Homes project really is utopia. Two years after installation, a survey of residents showed that most of them more imagined living in ecological construction.

This 1,160m2 prototype three-storey building with very low energy use consists of a two-storey office and 13 small family apartments.  Energy savings of approximately 65% are reached by: very high insulation (U-values of 0.10-0.12), controlled ventilation with preheating of infiltration through earth channels and heat recovery on exhaust.  The prefabricated wooden construction elements are produced locally.

Objectives and target audience

• Use of ecological and sustainable materials from Austria;
• Very simple and compact building shape, extremely reduced energy consumption;
• Reuse of non-preserved wood possible;
• Controlled ventilation systems with an air change rate of 0.5 – 0.7;
• High degree of prefabrication, therefore, short construction period (about 4.5 months including underground parking);
• Lowest possible energy consumption and use of organic materials without additional compared with a conventional construction.

Financial Resources and Partners involved

The total floor area is 1160m2 and construction costs were 1,625,400 Euro, 1400 €/m2

Process

The prototype in Ölz/Bündt is based on a number of principles:-
Variability: Besides the single-depth terraced houses, which have actually been built, it is envisaged to build double-depth houses, and buildings grouped around an inner courtyard;
Standardisation: The construction system, the facade, and the mechanical services are standardised units that can be used in the same way regardless of the site conditions;
Prefabrication: The design allows assembly without scaffolding, independently of weather and within very short time;
Mechanical services and building physics: Thermal insulation to the level of an ‘lowenergy- house’ or the standard of a ‘passive house’.  Air tightness is sufficient to operate controlled ventilation with heat recovery and additional air heating.

Results

The energy consumption of the building has been estimated using the dynamic thermal model TRNSYS.
The energy consumption was estimated at 17 kWh/m2.  Energy use is reduced to a value as low as 7.3 kWh/m2 by pre-heating of fresh air supply passing through earth channels, waste heat recovery from used air and small heat pumps.
Due to the low energy needs, the prototype house has no chimneys for heating systems.
Electrical heating covers the remaining heat demand.
A 33 m2 central solar heating facility on the roof produces.

Critical Success Factors / Challenges

This 1,160m2 prototype three-storey building with very low energy use consists of a two-storey office and 13 small family apartments.  Energy savings of approximately 65% have been reached due to good insulation (U-values of 0.10-0.12), controlled ventilation with preheating of infiltration through earth channels and heat recovery on exhaust. The prefabricated wooden construction elements are produced locally.