The photo shows ift installation expert Martin Heßler explaining to seminar participants the practical application of waterproofing systems with their advantages and disadvantages.

Trends in window installation

Actions to optimize assembly in the context of new EH 40 efficiency houses and energy-efficient building refurbishment

Reducing the immense consumption of resources and CO2 emissions in the construction and operation of buildings is a major challenge for politics, business and society if we still want to limit the consequences of climate change to a tolerable level.

This article was automatically translated from German into English with the help of


Unfortunately, there is no one lever that you only need to flip and then everything will be fine. The tasks are varied and one of them is to optimize the assembly of windows, façades, doors and gates, because this is mandatory if you want to improve the energetic performance of the building envelope. In new buildings, standardized solutions can be developed well, but they are becoming more demanding, especially for multiple-skin and highly thermal insulating exterior walls. For this reason, the focus of the publication is on the installation of construction elements in the energetic modernization of buildings, for which very attractive financial subsidies are also available.

The photo shows ift installation expert Martin Heßler explaining to seminar participants the practical application of waterproofing systems with their advantages and disadvantages.
Fig. 1: ift installation expert Martin Heßler explains to seminar participants the practical application of sealing systems with their advantages and disadvantages

New product developments

Based on the tests at ift Rosenheim, it is clear that most manufacturers of installation and sealing systems are constantly developing their products and having them tested according to the ift-Guidelines MO-01 and MO-02. The focus is on simpler use, faster processing and the expansion of applications (e.g. temperature range). For this reason, most suppliers are also developing so-called "liquid plastics" or "liquid membranes", with which complicated geometries such as penetrations of the sealing level, disturbances of the sealing level by fixing materials or the fixing of thresholds can be sealed simply and quickly. Here, it is also important to avoid typical processing errors already in the configuration of the product. The classic is coating thicknesses that are too thin, which can easily occur because the processor wants to save material or time. An effective means is therefore the use of thin and flexible grid structures, which simultaneously improve the resistance of the sealing and easily "expose" coating thicknesses that are too thin.

Three graphics show the cross-section of the plaster/grouted frame, the pre-wall mounting frame and modular frame.
Fig. 2: Different variants of 2-stage installation

Status 2-stage installation and pre-wall installation

The variety of advantages and applications of 2-stage installation are described in detail and with many practical advice in the free ift technical info MO-06/1 (available only in German). Since its publication in February 2022, new suppliers for this "quality installation" have been added and the co-editors confirm a significant increase in demand, especially for entrance doors. This is because the additional costs compared to assembly and rent for a "site door" are minimal. Planners and house owners see above all the advantages of significantly less damage during the building stage and an unbundling of the installation process, especially for high-grade units with shadings, vents, glass railings, etc. However, the suppliers of the 2-step installation must actively inform and convince and invest in the intensive training and motivation of the technical consultants and trade partners.

"Building sealing" challenge

French windows and/or "French doors" characterize the figures of modern architecture and thus the difficult interface between window installation and building sealing can be found on almost every construction site. The structural damage reports of recent years cite planning deficiencies, a lack of skilled workers, time pressure and increasingly complex specifications as the main causes of the many structural damages. It is therefore imperative that better consideration be given in planning to object-specific requirements with the necessary sealing measures and constructive compensation measures to ensure durable and fitness for use sealing. This problem is further aggravated by the increasing heavy rainfall events, because the high water pressure puts more load on the sealing.

To make this task easier, ift Rosenheim is working with representatives of all the trades concerned to draw up a guideline in which terms, specifications and design requirements are clearly specified. It is important to have a specified transfer point between the trades for standard installation as well as specifications for derogations in the case of recessed installation, in which normative sealing heights must be undercut, for example, in order to maintain barrier-free passability. The "maximum water accumulation height (max. WAH)" is newly introduced as an important parameter in order to obtain a clear design parameter for requirements and tests and thus the constructive solutions. This "water accumulation height" is also the dividing line for the requirements, because below it, water accumulation tightness must be ensured in conjunction with building sealing, and above it, watertightness must be ensured by the window manufacturer and/or fitters.

The graphic shows two principle representations of recessed installation, barrier-free on the right. Graphic is taken from the guideline for installation of windows
Fig. 3: Principle illustrations of a recessed installation, on the right with barrier-free design (image taken from [5])

Optimization of window replacement in existing buildings

The focus of the window market will increasingly shift to the modernization of existing buildings. This is because the energetic refurbishment of the building envelope (and thus the windows) is the biggest lever in the fight against climate change, which is also supported most strongly with subsidies. The bottleneck is not the manufacturing of new windows, but the planning and execution of the assembly. To make this task easier, ift Rosenheim wants to work with committed representatives of window manufacturers, installation companies and suppliers to develop a new technical information sheet. This will define the necessary requirements as well as describe constructive and building-physical solutions for the assembly of new windows in typical outer wall constructions (and their weak points). The new requirements for the dismanteling of existing windows (pollutants, disposal, treatment, etc.) will also be taken into account. The technical information is thus intended to promote the development of new, innovative assembly systems and to simplify and improve the planning, execution of assembly and its quality.

The picture shows the ift installation tool with new functions such as planning of the upper and lower structural connection for double-skin masonry and calculation of the length-related heat transfer coefficient ψ (Psi value).
Fig. 4: ift installation tool with new functions such as planning of upper and lower structural connection for double-skin masonry and calculation of the length-related thermal transmittance ψ (Psi value)

ift-Montageplaner (ift-installation tool) with new features

To facilitate the demanding task of assembly planning, the ift-Montageplaner (ift-installation tool) was developed as online software that can be used free of charge by fabricators, planners and fitters and enables simple and time-saving planning for object-related window assembly execution. The software focuses on simple operation as well as the avoidance of planning errors through intelligent program logic. The result of the planning is documented in the ift-installation passport and can be used as a template for the execution of as well as a silver for the professional and building-physical correct planning of the wall connection including the calculation of the minimum thermal insulation (fRSI-factor) and the dimensioning of the fixings. The installation tool has recently been extended to include the connections at top and bottom for masonry (neutral) cavity walls, and it will soon also be possible to perform the thermal calculation of the linear thermal transmittance ψ (Psi value). Further wall constructions and applications are in planning.

To the installation tool:


  1. ift-Guideline MO-01/1 - Structure connections of windows, Part 1: Method for determining fitness for use of sealing systems, ift Rosenheim, 1/2007 (German language only)
  2. ift-Guideline MO-02/1 - Structure connections of windows, Part 2: Method for determining fitness for use of fastening systems, ift Rosenheim, 6/2015 (German language only)
  3. ift Technical Information MO-06/1, 2-stage installation of windows and doors with pre-assembly door frames, published by ift Rosenheim, 2/2022  (German language only)
  4. Accompanying booklet to ift technical information MO 06/1, Statements on 2-step installation of windows and doors with pre-assembly door frames, ift Rosenheim, 2/2022  (German language only)
  5. Guideline for installation of windows and external pedestrian doors, Edition 8/2022, Gütegemeinschaft Fenster, Fassaden und Haustüren e.V., Frankfurt and ift Rosenheim, 12/2022, ISBN: 978-3-86791-483-3
  6. Leaflet Waterproofing connections to door and window elements:03-2018, Published by: Building envelope Switzerland, Association of Swiss building envelope entrepreneurs, Flat roof technical commission, 9240 Uzwill.  (German language only)
  7. Guidelines Building sealing - Connection to ground-deep windows and doors, Part 1: Planning, Part 2: Execution of. IFB - Institute for flat roofs and building sealing, Vienna 5/2020  (German language only)
  8. ift Technical Information MO-06/1 Assembly door frames, ift Rosenheim, Rosenheim 2/2022,  (German language only)

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