Catalog for heat bridges of window installation in renovation


The new thermal bridge catalog was developed by EIV as support to planners and architects in the EU Project AlpBC. IT provides planners with information, which is needed to plan thermal bridge effects and shading at window joints during renovation. The data allows the technical and economic optimization of the window through detailed energy demand calculations.

During the modernization of existing residential buildings, many concerns are taken into account. Interventions in the outer skin of a building have an impact on the architecture and thus on the environment. Conversions and extensions engage in the overall spatial concept.

Careful planning makes it possible to foresee the consequences of selected decisions in detail and to estimate thus expected cost safely.

Two issues play an important role in all measures: choosing the right building material and the way how it is installed.

The window is the most stressed part of a residential building. Over the past 15 years there has been a rapid development in the window glass and frame materials. The U-value of the glass was constantly improved and thus the energy loss is reduced on a fifth. The window glasses reach today -thanks coatings and fillings with inert gas insulation- values ​​up to 0.4 W / (m 2 K). Good energy technical standard are glasses with a U-value of 0.6 W / (m 2 K). Further improvements were made ​​in the glass edge seal. Window frames with insulated frame profiles or special wooden frame with air chambers, reach U-values ​​of less than 0.8 W / (m 2 K). But still the installation of the window is often not well planned and unexpected losses turn a very good window into a medium performance window.

  • For the catalog of thermal bridges a variety of window connecting situations were investigated.
  • Three outer wall types in massive and timber construction
  • Three renovation alternatives – stock with window replacement, renovation as a low energy house and refurbishment with Passive House components (with U-values ​​of 0.130 to 1.346 W / (m 2 K))
  • Nine types of frames with different energetic quality
  • Four types of window installation

A total of 164 variants were analyzed according to the described matrix.
For all investigated variants, the following variables were determined:

  • Thermal bridge loss coefficient top, sides and bottom
  • Geometric data for the calculation of shading
  • Additional data to evaluate the risk of damp (including minimum surface temperatures, maximum non-critical room humidity)

The catalogue allows planners to control their planning by some clicks in the quick guide of the pdf document and makes it easy to recognize the influence of different decisions.

The catalogue is available in German on the EIV homepage: (Wärmebrückenkataloge)

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