Case study 1: Windows

Improper installation of windows - causes, consequences and expert assessment

Mission and initial situation 

The client contacted me after leaks and draughts were discovered in several window elements in a new building project. 
A site inspection revealed that the windows in question were aluminum windows that had been installed as part of the shell construction. Moisture ingress and condensation formed after just a short period of use. 

This case study shows typical damage caused by improper window installation - from leaks and thermal bridges to mold growth.

Damage pattern detected 

• Missing or improper sealing of the connection joints 

• Thermal bridges in the reveal area due to non-continuous insulation 

• Insufficient fastening of the window frames to the supporting structure 

• Leaking connection joints in the area of the window sills 

• Partially incorrect installation of the sealing profiles and defects in the film bonding 

The damage led to condensation, mold growth in the connection area and increased energy loss. 

Root cause analysis 

The causes can be traced back to several execution errors: 

1. Non-compliance with the manufacturer's specifications for the installation of aluminum windows according to DIN EN 14351-1. 

2. Faulty sealing contrary to the requirements of the RAL installation guidelines („Installation guide“). 

3. Lack of separation between inner and outer seal, This allowed moisture to penetrate unhindered into the connection area. 

4. Inadequate control during construction - No documented acceptance of the sealing work. 

Normative evaluation 

According to VOB/C ATV 18360 „Metal construction work“ and DIN 4108 Part 7 (thermal insulation and energy saving) applies: 

Window connections must be permanently airtight and impermeable to driving rain. 
The installation must not cause any thermal bridges and must be carried out in accordance with the rules of technology. 

These requirements were not met in several places. 
In the spirit of DIN EN ISO 9001 (quality assurance) an intermediate inspection during assembly would have been mandatory. 

Consequences of the shortage 

• Energy losses due to thermal bridges 

• Mold formation and material damage in the connection area 

• Reduction in noise protection 

• Visual impairments 

• Limited usability of the windows 

In individual cases, improper installation can also Static risks especially with large-format window elements. 

Recommended measures 

• Dismantling the affected connection areas 

• New construction of the inner and outer seal in accordance with RAL installation guidelines 

• Check the fixing points in accordance with the manufacturer's installation instructions 

• Documentation of the sealing work with photos and test report 

• If necessary, additional thermal insulation in the reveal area 

For future construction projects, a Construction supervision by an expert is recommended in order to detect assembly errors at an early stage. 

Summary 

The identified defect „improper installation of the windows“ constitutes a significant execution errors represent. 
Non-compliance with the recognized rules of technology leads to moisture damage, energy losses and limited usability. 
Professional installation according to DIN EN 14351-1, DIN 4108 and the RAL installation guidelines would have prevented this damage. 

Note from the expert 

As a publicly appointed and sworn expert for the metalworking trade, I assess the execution of window, door and façade work independently, comprehensibly and on the basis of the applicable standards and technical regulations. 

Further information

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