THERM-opti-BALCONY-P2 - Thermal Optimized Renovation of Balconies Phase 2: In-Situ-Pilot-Station

Pre-cast cantilever balconies represent a particular problem in the case of thermal rehabilitation of buildings. With the THERM-opti-BALKON-System a solution is currently being investigated under laboratory conditions. Phase 2 aims to create an in-situ-pilot-station. The most important object of study is the long-term behavior of the THERM-opti-BALKON-System.

Short Description

Starting point/Motivation

During the subsequent attachment of thermal insulation on exterior walls in case of thermal renovation of existing buildings, free cantilevered balconies represent a severe problem. Commonly employed techniques in practice are

  1. to tear down the balconies before the attachment of the thermal insulation and to rebuild them as a self-supporting construction with columns on foundations, which is in many case technically not feasible or from an aesthetic point of view undesirable, or
  2. to preserve the existing balconies leading to severe thermal compromises, because of the thermal bridge in the balcony area through the new attached thermal insulation, or
  3. to omit the balconies after the thermal renovation of the building which leads to a significant reduction of habitability to a massive decrease in value of the real estate.

Contents and Objectives

In the research project THERM-opti-BALKON, the THERM-opti-BALKON system was investigated under laboratory conditions. This system enables the thermally decoupled new construction of balconies on thermally renovated facades with a concrete screw back anchoring system. These developments are taken up in the project THERM-opti-BALKON-P2 (phase 2) and are further developed to „System II". In order to minimize the installation effort, only one concrete screw with a large diameter is used in the area of load introduction per anchoring point. Furthermore, the thermal decoupling is adapted to the high requirements for usage in low-energy and passive houses. To this end, its thickness is raised to the insulation thickness required for such buildings up to 200 mm. „System II" is then implemented in an in-situ test facility on a 30-year-old building under real conditions with the possibility of dismantling in case of project failure. In this pilot application, important insights into the practical installation of the system solution can be obtained.


In a first project step, a survey is carried out on the building, on which the in-situ test facility is installed. Here, basics for planning, design and dimensioning are collected. Based on this, the in- situ test facility can be designed and pre-dimensioned. In parallel laboratory tests the static load capacity of „System II" is investigated. After all necessary planning and investigation steps have been completed, the in-situ test facility is built and is equipped with a long-term monitoring system.


In this project, the THERM-opti-BALKON system solution can be successfully developed into SSy- stem II". In experimental investigations at the component level as a preliminary stage of the pilot application, the static load bearing capacity of this system is demonstrated. In addition, the component tests allow a first competing comparison with existing market solutions. Thus, in addition to the mechanical properties, the installation effort and the expected installation costs of „System II" can be compared with those of conventional market solutions. Further thermal numerical simulations of the thermal bridging loss coefficient of „System II" allow a comparison with market solutions. Both, the installation effort and the thermal performance of the thermal decoupling system can be significantly increased by larger possible insulation thicknesses of up to 200 mm. This enables application in low-energy and passive houses. During the implementation of the in-situ test facility, important findings can be derived for further practical application. Statements on the durability of the system solution will be available in the coming years.

Prospects / Suggestions for future research

The present project is the basis for the development of a practicable and cost-effective thermal decoupling system. Especially for the development of a market-ready solution with large-scale production, need for research is still present in several areas. From a technical point of view, the current solution and the location of the black and white connection is not ideal. On the one hand, the effort and costs of welding are far too high. On the other hand, the suggested solution requires an additional step to ensure corrosion resistance. The in-situ test facility built in this project will be monitored above the duration of this project. Hence, further insights into the long-term behaviour of the system solution are expected.

Project Partners

Project management

Dipl.-Ing. Nikolaus FLEISCHHACKER, BSc.: University of Innsbruck, Institute for Structural Engineering and Material Sciences, Unit for Concrete Structures and Bridge Design

Project or cooperation partners

  • FEN Sustain Systems GmbH
  • Architekt DI Gerhard Hauser

Contact Address

Dipl.-Ing. Nikolaus FLEISCHHACKER, BSc.
Technikerstraße 13
A-6020 Innsbruck
Tel.: +43 (512) 507 63306
Fax: +43 (512) 507 63399