As we know, the Thermal Properties of window glazing play a big role in the performances of the whole window. So it’s important for us to choose the right window glazing for our upvc windows.
There are certain criteria which help to evaluate the insulation properties of uPVC window glazing
U-factor defines how much heat is lost through uPVC window glass or uPVC window as a whole. Therefore it is best to look for uPVC windows with the lowest U-factor possible. This is especially relevant for colder climate regions, where heating bills are high.
G-value indicates the amount of solar heat that is allowed to enter the building through the uPVC window glass. Depending on the climate, more or less solar heat may be desired. In colder climates, window glazing with high G-value is recommended, since it allows more heat inside the house and thus the house gains passive solar heating. In hot climates, there is a risk of overheating the building in summer, therefore uPVC windows with low G-value are recommended. Low G-value glass helps reduce the heat, and the expenses on air-conditioning may be significantly minimized.
Visible Transmittance (VT) is another important coefficient that is worth considering when choosing glass for uPVC windows. It measures how much visible light is allowed to enter the building through the uPVC window glazing. Usually glass that blocks solar heat (solar control or reflective glass) also reduces visible light, which is not favourable. Generally, the best uPVC window glazing is the one which reflects the undesired solar heat, but transmits most of the visible light.
Passive house glass
Passive house glass is designed to achieve the best thermal properties. Passive house glass units are composed of three sheets of glass; generally, the wider the triple glazed unit, the better thermal properties are achieved. Passive house glazing helps reduce the heat loss and save money on energy bills. They are typically composed of one clear float pane and two low-e panes. Low-e or low-emissivity glass has a thin layer of metal oxide, which reflects heat back into the room. This is particularly important in winter, because this type of uPVC window glazing minimizes the loss of heat. Low-e glass is usually spectrally selective; it reflects a large proportion of solar heat, but lets light into the room. To achieve the best effect, low-e panes must be located on the interior side of the uPVC window glazing. It is important to note that thermal properties of a glass unit can be heavily influenced by the gas that fills the cavities between the sheets of glass. Inert gases such as Argon or Krypton help lower the U value. For the best result, consider warm edge spacer bars, as the edges of uPVC window glazing are the most prone to heat leaks. Passive house glazing is recommended for uPVC windows in temperate and cold climates, especially when demands for energy efficiency are high, e.g. when building a passive house.
Safety glass has two main functions:
- Protection against burglars,
- Prevention of injuries in the case of shattered glass.
Safety glass is more resistant to mechanical impacts; it takes much more effort and special tools to break it. In some special cases, safety glass is bullet-proof. Additionally, safety glass is manufactured in a way that it would not pose danger if shattered. The shards either stay glued to the surface of the glass, or the glass breaks in small blunt cubes. According to the building regulations in many countries, safety glass is required in all floor-to-ceiling uPVC windows, as well as in uPVC doors. There are three types of safety glass for uPVC window glazing: toughened glass, laminated glass and fire-resistant glass.
Warm edge spacer bars
Spacer bar is a long and narrow piece of metal or other material that separates sheets of glass in a double glazing or triple glazing unit. The purpose of the spacer bar is to hold the panes together in a uPVC window glazing unit, as well as to absorb any humidity that appears inside the unit, between the sheets of glass. For this reason, spacer bars are made from a sturdy material, which is filled with desiccant so that to absorb the vapour.Until recently, spacer bars were made almost exclusively of aluminium.However, aluminium is a metal and therefore a very poor heat insulator. In cold months, the temperature in the centre of such uPVC window is very different from the temperature in the corners (it is colder near the spacer bars). This causes condensation on uPVC windows glass, as well as a drop in temperature in the room.In order to prevent this, alternative spacer bars have been designed.Warm edge spacer bars for uPVC window glazing units are usually made of structural foam, polymers or glass fibre. Warm edge spacer bars is a good way to improve the overall performance of your new uPVC windows.