The phenomenon of “ringing” of mullions in insulating glass units is not the result of negligence or carelessness during the production of the glass, but is the result of the overlap of normally occurring pressure changes in the insulating glass units and external (atmospheric) conditions.
Pressure changes occur as a result of temperature changes: in summer the pressure increases as a result of the glass heating up (the glass “inflates”), and in winter the pressure decreases as a result of the glass cooling (the glass becomes concave).
The operation of the moisture absorber placed in the spacer frames (absorbing moisture and reducing the pressure in the space between the panes) also affects the shape of the glass. Glass deformation is such an insignificant and hardly noticeable phenomenon that it is usually omitted when talking about windows.
However, when using mullions in insulating glass units, the above-mentioned changes in the shape of the glass cause the distance of the aluminum mullion from the glass to vary at different times of the year. When using an insulating glass unit with a standard thickness of glass panes and an inter-pane space (4-16-4), the problem practically does not occur, but in an insulating glass unit made with a larger glass thickness, e.g. (6-12-6), the probability of contact increases mullion with glass. (thicker glass deforms less, but the space between the panes is correspondingly smaller (12 millimeters instead of 16) and therefore the distance between the mullion and the glass panes is very small).
To prevent the glass from touching the mullion and the “ringing” effect, colorless overlays made of flexible polymer are used.
However, even the use of these overlays does not always satisfy customers, and some people complain about the “jingling” of the muntin in the glass. Here, other external circumstances should be taken into account – starting from the dimensions of the glass (the larger the size, the greater the possible deformation of the glass), the location of the building in relation to the cardinal directions and exposure to wind gusts.
The size of the glass is the factor that affects the use of the appropriate glass thickness, but for certain dimensions, glass of the same thickness is used and for typical glazing made of 4 mm thick glass, the glass may have a maximum allowable dimension of 2500 mm x 1400 mm. The location of the building in relation to the cardinal directions is, contrary to appearances, also an important factor – especially in winter, when the northern and western facades are subject to lower temperatures and, therefore, greater glass deformations.
At low temperatures (e.g. below 10 degrees Celsius – and these have been happening quite often in our country recently), the polymer overlay glued to the muntins hardens and its protective function decreases – and when it comes into contact with the glass as a hard element, it clicks. However, the use of these overlays
it is not required by any technical conditions and in the case of the so-called “Viennese” mullions it is not used.
And finally, the wind: its influence is always visible, even in the case of windows without glazing with mullions.
While windows without mullions shake “silently” because the window profiles are a rigid element (glued laminated wood or multi-chamber PC with steel reinforcements) and the use of multi-stage seals dampens movements and while such shaking does not arouse anyone’s emotions, the occurrence of invisible but audible “knocks” ” or “ringing” in the windows is often a cause of irritation.
Unfortunately, the glass cannot be stiffened. Therefore, it should be expected that the house designer will be able to determine the operating conditions of the building, and then avoiding the above-mentioned phenomena will not be a problem and will help avoid misunderstandings and complaints.
