Explanation of the problem of knocking of muntins mounted in insulating glass units

In response to numerous inquiries, as well as complaints resulting from the knocking of inter-pane muntins installed in plastic, wooden or aluminium windows, we would like to explain that this phenomenon may occur due to several of the following reasons:

  1. When the muntin height exceeds 1000 mm;
  2. The area of the glass pane is large, e.g. greater than approx. 2 m2, and it is divided, for example, into 4 fields;
  3. The width of the inter-pane space is greater than the thickness of the muntin together with silicone protections glued to the junction of the muntin bars, especially for muntin bars with a width of 8 mm;
  4. Windows whose glazing has muntin bars and is installed in places where there are vibrations and excessive, improper loads due to slamming (e.g. from traffic or draft), which may cause the silicone protection devices to peel off or the muntin fittings to loosen;
  5. Changes in pressure or in temperature, may cause the expansion and contraction of aluminium muntins, just like any other material. It may also cause the formation of gaps up to 1-2 mm despite our accuracy in making muntins.

The above-mentioned conditions very often occur simultaneously, which causes the intensification of this phenomenon, and our company has no influence on it. Our system of production and installation of inter-pane muntins is designed in order to provide the best protection against these and other possible problems, e.g. by mounting silicone protection at the junction of muntin bars, plastic joints and ends. Therefore, if the muntin bars made by our company have all these protections, the knocking phenomenon is most likely due to factors beyond our control. Additionally, our five-year warranty covers the transparency and tightness of the insulating glass units.
In conclusion, we would like to inform you that this phenomenon will not be recognized by our company as a basis for complaints about insulating glass units, unless the muntin bars were not made properly. We hope that our explanations will be properly understood by

SPEC-GLAS Sp. z o.o. - Producer of glass insulating units
Szczecin ul. Kmiecika 10 tel. 91 464 91 30
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