The new generation of Low Emissivity glass.
This type of glass allows light to pass through it, while at the same time providing thermal insulation.
This is the result of a special metal coating on the interior of one of the two glass panes (in double glazing), which exhibits high reflectivity to infrared radiation.
This coating consists of various microscopic metal oxides which impede heat transfer from the outer side of the glass to the inner side and vice versa.
This means it does not allow heat transfer from the exterior of the house to its interior and vice versa.
These coatings can be completely transparent, or have various colour hues. The result is a glass pane which, in its final form, has the desired shade (tinted, bronze, pale blue, etc.).
When analyzing the thermal losses as a result of the building's structural elements, we come to the following conclusions :
• 20% of heat loss is due to the roof
• 25% of heat loss is due to the walls
• 20% of heat loss is due to the flooring
• 35% of heat loss is due to the windows
Soft-coated Low-E glazing doesn't only reduce the amount of heat transferred from the building's exterior to its interior, it also filters solar radiation.
This allows it to greatly reduce the permeability of ultraviolet and infrared radiation—which results in the wear of carpets, curtains, furniture etc.—by up to 70%.
All of the above are determined by certain energy coefficients
There are three important coefficients when selecting the type of glass:
Α) Uvalue or Κ - value W/m K: heat-transfer coefficient
it expresses the rate of heat loss per square meter of glass between its inner and outer surface of the glass pane, and is determined by a surface's ability to absorb or emit heat.
The lower the emissivity, the lower the heat-transfer coefficient K, and, therefore, the more energy-efficient the glass.
Β) Solar Factor - g: solar factor,
ε it is one of the most important factors and expresses the percentage of overall solar energy/heat passing through the glass to the interior space.
Its values range from 0-1.
Due to the intense heat during Greek summers, it is very important to minimize its value (0), otherwise the glass functions as a heat passage that results in excessive interior heat, which overburdens the air conditioning units.
Γ) Light Transmission - LT: light transmission,
ε it expresses the percentage of visible light passing through the glass.
The higher the coefficient, the more light passes into the space.
A low light transmission coefficient increases the consumption in artificial lighting systems.
The ideal values of this coefficient range from 60% - 80%.
Therefore, for an optimal energy-efficient result, we should select glass panes with :
· Low Uvalue
· Low g
· High LT
In the summer, those panes :
1. reflect the sun's infrared light
2. act as a shield against indirect heat from the surrounding area – facilitate cooling
3. reduce cooling costs (by up to 35%)
4. reduce artificial lighting costs
In winter, the panes :
1. act as a shield against heat trying to escape the interior – provide more efficient thermal insulation
2. reduce heating costs (by up to 35%)
Low-E glazing allows us to manage solar light to our advantage, creating a comfortable environment with the lowest possible cost, both financially and in terms of energy-consumption.
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