Pilkington K Glass™ should not be used as single glazing.

Effective U value 

In the case of windows and glazing, because they admit the sun's energy, the U value concept can be taken a step further Even in the winter the sun can shine and help to warm a room. 

Over a typical heating period the amount of useful heat from the sun entering through windows can be subtracted from the normal U value (a measure of the heat leaving through the windows) to give an overall "effective U value" This is dependent upon the direction the window faces. In the case of south facing windows with Pilkington K Glass™ double glazing units, the normal U value of 1.9 W /m˛K is reduced to an Effective U value of virtually zero. In other words, the amount of heat lost is balanced by the heat gained from the sun.

Effective U value can simply be regarded as "heat out minus useful heat in".

Appearance 

Pilkington K Glass™ has high light transmission and appears virtually the same as clear float glass. However, in rare instances of strong oblique lighting, the coating may be seen as a transparent film. This is simply a transient visual effect which can be considered positive evidence of the coated surface being present.

Further evidence of the coating's presence is through the very minor effect it has on white light transmission. This effect is so small as to be generally unnoticeable However, when a light coloured object or material is in close proximity to the glazing, dependent on local circumstances and conditions, a slight darkening can be noted. 

Because Pilkington K Glass™ is so neutral in appearance, it is recommended that its presence in a double glazing unit is confirmed on installation. 

This can be achieved by the use of a coating detector which unit manufacturers or installers should have available.

In certain extreme environmental conditions, low emissivity glasses might increase external condensation.

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