Technical Data>Heat Transfer
Heat transfer always occurs from one region or body of high temperature to another of lower temperature.
Preventing heat excess into the interior during summer and avoiding interior heat, released from heaters, to the exterior during winter are two aspects to bear in mind when selecting the right glass for a building.
The importance of these factors is twofold: firstly, because it is on them that heat comfort in the interior will depend; and, secondly, because they will determine the amount of energy consumption of building for as long as the life of the products.
Reaching a sensible decision on this matter is not an easy task since it should comprehend several factors that have an effect, either directly or indirectly, on how heat transfer performs through the glasses of a building structure.
Among other important factors are the glass size and surface–whether it is vertical or horizontal–, the weather in that particular region, the solar orientation upon the building front facade, the purpose and function (to be) served by the building, the solar shading devices–in exteriors or interiors-, etc.
Solar Control
When solar radiation reaches the glass, a part of such radiation is rejected towards the exterior, another part goes straight through the glass into the interior, and the rest becomes absorbed by the mass of the glass. Of absorbed part, two thirds are rejected towards the exterior, with the remaining third reaching the interior. The degree of solar heat transfer varies with glass thickness, colour and reflecting coating employed.
Letting solar heat in is usually desirable as it is natural heating. Where the heat is excessive, however, comfort decreases and/or so does the use of cooling devices.
Colourless Float glass let almost all solar heat radiation in. Float glass is tinted in its mass -Grey, BronzeandGreen, normally granting good control over solar radiation.
High performance body-tinted glass show similar values to those shown by blue, bronze, and green pyrolytic reflective glasses. Reflective glasses usually present the highest solar control performance. While heat transfer is reduced by solar control glasses, so is the amount of visible light reaching into the interior of the building.
A sensible decision should not leave out either factor, both normally depending on the size of the glass surface, the orientation of the building front facade and the purpose or function (to be) served by the building.
Whenever solar control glass integrates DIGs, its shading coefficient is improved. When choosing solar control glass, assessment must be pursued on the potential risks of encountering an excessive heat differential, in which case, the glass will require to be insulated against heat in order to preclude any possible cracking.