What exactly do the U and g value mean?

Thermal Insulating Glass


Technical parameters
The basic quality required of insulating glass is the presence of increased thermal insulation, i.e. the greatest reduction of heat loss.  


U value
• The basic measure unit for establishing the heat loss of a construction segment
• The value indicates the amount of heat that passes through one m2 of a construction segment in a time unit during  a temperature differential between indoor and outdoor air of 1 degree Kelvin
• The measurement unit is W/m²K
• The lower this value is the better the thermal insulation of the construction material
• A low U value is the most important characteristic of insulating glass
• Low heat loss from better thermal insulation leads to higher surface temperature of the interior windowpane and thus higher comfort in the room
• Enables the use of less heating equipment and as such offers both economic and ecological advantages 


G value
• The coefficient of the permeability of total solar radiation energy stated as %
• Composed of the direct transmission of energy and the secondary dispensation of heat of the glazed surface toward the interior, which occurs on the basis of absorbed solar rays.
• The sun can heat a room only by glass and thus also contribute to heating without any additional expenses
• What is welcomed in winter can be unpleasant in summer, because gaining energy through solar radiation means heat
• The correct course is high thermal insulation, which means a low U value combined with a G value that is not too high
• The technological standard has become insulating glass with a plated layer
• Formed by at least two panes of glass, one of which is coated with an extremely thin layer of high-grade metal, which radically reduces thermal losses