If the glass breaks due to thermal stress it is not the indication of low quality of the glass - it is a phenomenon caused by the properties of the material itself and the the effect of surrounding environment. Therefore the thermal stress breaks are not cevered with the warranty of the glass. If the glass heats and the tmeperature differential reaches to critical levels, tensions (stress) in the glass may exceed critical threshold and glass breaks.

Most common risk factors include objcects too close or against the glass and curtains (blinds etc.) which are too close to glass. But also the external shadows on the glass, additional safety, sunprotection and other type of foils attached to the glass. 

Typical indication that occuring break is caused by thermal stress is 90-degree angle related to the glass edge and the crack itself is winding on the surface (so to say sinusoidal). In case of extreme tensions a fountain effect may appear so that many cracks start from one point.

What can one do...?

While planning curtains or blinds consider the safe distance from the glass - at least 50 mm from the glass internally. This way air can move and the glass surface does not heat too much.

In architectural plans engineers must consider possible shadows of construction elements: roof edges, balconies etc. Large glazing such as high windows and doors should be with the safety glass according to building regulations. But in regards of thermal stress just laminated glass in not sufficient - thermally toughened glass should be used (also within the laminated glass if that is needed due to safety considerations).

Only 100% sure solution to avoid thermal stress cracks is to use thermally toughened glass for all the glasses in insulated glazing unit (internal and external glass and in case of 3-glazing also the middle pane).

Special foils on the glass

- If applying special foil on the external surface (e.g. for security or sun protection) use thermally toughened glass for external pane. The internal (and middle pane in 3-glazing) are with the lower risks but some risk still remains.

- If applying special foil on the internal surface (e.g. for security, safety or smart foil) use thermally toughened glass for internal pane and we recommend thermally toughened pane for the middle pane in 3-glazing unit also. The external pane is with the lower risk but some risk still remains.

Also consider while planning your windows and doors, if instead of the additional special foils the similar desired functions could be achieved with the same type of glass e.g. sun protection LowE or safety or security glasses.

Blinds and curtains

If the blind system is integreted within the glazing unit (between the glasses) then -

- 2-glazing unit should be made of thermally toughened glasses both internal and external pane;

- 3-glazing unit the internal and middle pane should be thermally toughened glass. The external pane is with the lower risk but some risk still remains. Glazing manufacturer recommends all 3 panes to be thermally toughened.

Blind and curtains inside the room:

- Safe minimum distance between the glass and blinds/curtains is 50 mm. In this case thermally toughened glass is not needed (NB! Always consider the building regulations for safety!!!)

- If the blinds/curtains are closer than 50 mm use thermally toughened glass for internal pane. The middle pane in in 3-glazing unit and the external pane are with the lower risk but some risk still remains.

Read more from Wikipedia or find out with web search using "thermal break in glass" or "thermal stress glass breakage" or similar search words.

External condensation is caused by cooling of the external glass pane. Condensation occurs in the middle area of the glazing. Mostly it happens during spring and autumn when the air humidity is higher and the air temperature lower. In some extreme situations during winter it may happen that external surface of the glazing is covered with ice for a short period. Although it may seem unpleasant external condensation is actually an indication of high energy efficiency - internal heat does not warm the external glass pane.

Illustration of external condensation: internal heat does not reach the external pane of glass	Illustration of internal condensation: internal air humidity is too high

New windows and doors

While planning new house, we recommend following: 3-glazing ensures better energy efficiency compared to 2-glazing. Thus 3-glazed windows are less likely to form internal condensation (but higher probabilty for external condensation). To reduce internal condensation risks significantly, we recommend warm edge spacer solutions (e.g. Swisspacer; Chromatech), which have better insulation properties compared to aluminium spacers. In 3-glazing 2 glasses with LowE coating are used by default.

Existing windows and doors

Before you decide that something (really bad) has happened with your windows and/or doors because there's condensation, you should consider air humidity inside the house. During heating season the relative internal air humidity should be Rh = 25...45%. It is important that rooms have proper ventilation to ensure quality of internal air. Even with the windows with best available thermal insulation one may end up with the condensation if the internal climate conditions meet certain levels. 

To read more download this flyer (PDF)

Attention should be paid to the following features:

• Energy efficiency;
• Safety;
• Sound insulation;
• Sun protection.

Find out more from SGG Glass Flyer (PDF)

Energy efficiency

The energy efficient glazing can reduce heating costs. Metaphorically: one should not throw money out of the window.

With Viking windows and doors You can reduce heat losses by choosing the most suitable products with the best glazing available. We recommend to use SGG Swisspacer for warm edge solution. Argon filled cavities are Viking's standard solution.

Glazing unit with Argon filled cavity and selective (low-E) coating helps to increase energy efficiency (reduce thermal transmittance). The double glazing unit is equipped with one pane with low-E coating; the triple glazing unit has two glass panes with low-E coating. The Argon gas inside the cavity reduces convection inside the cavity. This type of glass heats up as fast as normal, but radiates less heat out of the room.

Thermal transmittance is expressed with U-value (Ug). Lower U-value means better insulation.

Safety

To increase safety for users laminated or toughened glass should be used.

Toughened glass	Laminated glass

The lamination means that for one glassa pane two glasses are glued together with special film. If the glass breaks the film keeps pieces together. The toughened glass is manufactured by heating and fast cooling of the glass. As a result if breking it forms small particles. This way the risk of insures is minimized.

Sound insulation

For increased soud insulation glass panes with different thicknesses should be used in the glazing unit: 6 mm glasspanes and 8 mm laminated glass are the most common options.

Sunscreen

In spring and summer inside temperature can rise due to increased sunlight. In the buildings with a large glazed facades the amount of energy used for cooling can be bigger than heat demand. If You need or want to keep a lower temperature, sun protection glass should be used. This kind of glass is usually tinted, or with a special coating. Sunscreen selective ensures low solar factor and good thermal insulation at the same time.

Sun protection is indicated by the g-value (solar factor). The lower the g-value, the more stable the temperature of the room.

Properties of glazing units

Viking windows can be used in a wide range of glasses as described above. In a glass unit can be combined in different colors in glass and vitraažklaase.

Below are the Viking Window 2 times and 3 times the standard package, thermal glass (Ug) and solar radiation factor (g):

Stained Glasses

Download brochure: stained glasses (PDF 2.2 MB - Estonian/English)

Classic stained glass

This technique is best described as what we are used to see in churches. It is the oldest technique in stained glass history and it has changed very little. With this technique coloured glass is used and every piece of glass is cut by hand. The pieces are assembled with H-shape lead came. After assembling the glass, lead came is soldered on both sides. This technique fits well with classic geometric and diamond patterns. This type of stained glass is best for restoration works and old historical buildings.

Tiffany stained glassTiffany stained glass

All the pieces are cut by hand from coloured glass. Cut edges are covered with self adhesive copper foil. After that pieces are laid side by side and copper foil is soldered. Coating connects the pieces. Tiffany technique allows very complex patterns with small details. This technique goes especially well with nature motives and flower patterns. Main visual difference compared to classic stained glass is that lead lines on tiffany glass vary throughout the work. Usually the lines are thinner than on classic stained glass.

Art film stained glass

For this type of stained glass the pattern covers one whole sheet of glass. First, self adhesive lead strips are laid on the glass according to a drawing. After that, the glass is turned over and coloured art film is laid where necessary. Edges of film are covered with lead strips according to lines below. Art film stained glass is visually quite similar to other types of stained glass. Art film stained glass does not deform in time, so larger areas can be covered with glass.

Frequently Asked Questions:

For How Long Argon Remains Inside Glazing Unit?

Glazing units are manufactured inside Argon environment. Glazing cavities are sealed with elastic material to hermetic separation from surrounding. The European quality standards for insulated glazing units allow the reduction rate maximum 1% a year for Argon. This means that during the lifetime of the window there is no significant decrease in thermal insulation.

Why Does the Condensation Occur?

Condensation is a natural phenomenon which hapens as a solution of temperature drop below the dew point. Usually there is always some water vapor in the air. When the temperature of the objects and the air is lower then the dew point, condensation occurs.

External condensation is caused by cooling of the external glass pane. Condesation occurs in the middle area of the glazing. Mostly it happens during spring and autumn when the air humidity is higher and the air temperature lower. In some extreme situations during winter it may happen that external surface of the glazing is coverd with ice for a short period. Although it may seem unpleasant external condensation is actually an indication of high energy efficiency - internal heat does not warm the external glass pane.		Internal condensation is caused by high internal air moisture and cooler glazing surface. Mostly it starts on the bottom edge of glass. Internal condensation is a complex matter with many causes including internal air moisture, room temperature, internal air convection, ventilation, heating system etc.

Why Choose SGG Swisspacer?

The practical result of choosing SGG Swisspacer is lower risk for internal condensation.

The spacer bar inside glazing unit is responsible for the linear thermal transmittance. It forms a cold bidge. To reduce heat loss in glazing edge area materials with lower thermal conductivity should be used. SGG Swisspacer with its plastic is one example of warm edge technology applied to improve thermal comformt.

Intended use:

• Front doors - typically with handle and key locking cylinder (as an alternative on the interior side a turn knob is used); use and size of glazing varies - glass provides view to outside or is used only as a design element.
• Terrace doors- (balcony doors) typically with more simple window-type hardware (e.g. window handle, espagnolette with similar functions as windows etc.). Sometimes handle is used only on the inside. Cylinders for locking can be used - if the handle is on both sides. Mostly with the max size glasing unit to maximaze the light gain.
• Sliding doors - opening function is sideways sliding. May be also combined with upwards, outwards, inwards or tilt function - depending on the hardware used.

Front door	Terrace door	Sliding door

Number of door leaves

1 leaf door	2 leaf door (aka double door; french door)

Panel doors and profile doors

Cross section of panel door	Cross section of profile door

Panel door leaf is a composite product of timber frame covered with weather proof plywood "skins" (including moisture protection) and filled with insulation material. With the modern CNC technology different grooves and glazing options can be used for design purposes

Profile door leaf is assembled of glue-lam timber profiles. In the openings of the leaf either glass or insulated panels can be used. 

Check for more:

Panel door designs

Profile door designs

Available door designs (click on the images below to see more):

2-glazed doors

3-glazed doors