Introduction

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.