THERM-opti-BALCONY: Thermal Optimized Renovation of Balconies

Pre-cast cantilever balconies represent a particular problem in the thermal renovation of buildings. The central goal of this project is the development of practical and cost-effective mounting solutions for the thermally decoupled reconstruction of balconies on building frontages and achieving a significant increase in the energy performance of the thermal renovation measure.

Short Description


Starting point/motivation

As far as attaching a thermal insulating posteriori on exterior walls is concerned in the course of the thermal renovation of existing buildings, pre-cast cantilever balconies represent a particular problem. According to the state-of-the-art balconies, the common custom is

  1. to tear down the balconies before the attachment of the thermal insulation and to reconstruct them thereafter as a self-supporting construction with posts on distinctive foundations, which is technically not feasible in many cases or aesthetically unwelcome, or
  2. to preserve the existing balconies which leads to severe thermal compromises because the balconies form heat bridges through the newly mounted insulating, or
  3. to omit the balconies after the thermal restoration of the building which leads to a blatant deterioration of the indoor environment quality and to a loss in value of the real estate.

Contents and goals

The project at hand aims to develop solutions which facilitate the thermally decoupled rebuilding of balconies on thermally renovated building fronts, thereby focusing on optimum practicability and cost-effectiveness.


To reach these goals, the project team considers mounting systems based on concrete screws to be the most promising approach. Because concrete screw connections of overhanging plate-like building components like balconies have not been investigated systematically up to now, the project breaks technical new ground and a number of fundamental scientific investigations and development work needs to be executed.


The thermal decoupling system "System I" is developed within this project. It allows a thermal decoupled reconstruction of balconies in the course of refurbishment. Therefore it contributes to a significant improvement in thermal rehabilitation. For the development of this system, basic principles of fastening technology for concrete screws have been investigated in a large number of experimental tests. In particular, this is the transfer of force from the concrete screws into the anchor base of reinforced concrete under tensile load. For this purpose, bond-stress-slip laws can be derived.

These allow the development of a numerical simulation model, laboratory tests on component level and a dimensioning approach.

Prospects / Suggestions for future research

With the THERM-opti-BALKON-P2 project the THERM-opti-BALKON project is continued. The further development of the thermal decoupling to system II and its pilot application provides necessary knowledge for a new product development.

Project Partners

Project management

University of Innsbruck, Institute for Structural Engineering and Material Sciences - Unit for Concrete Structures and Bridge Design

  • Univ.-Prof. Dr.-Ing. Jürgen FEIX
  • Dipl.-Ing. Nikolaus FLEISCHHACKER, BSc.

Project partners

Contact Address

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