There are a number of specifications to consider when choosing uPVC windows. Below are explanations of the most important points with the jargon explained so the layman can understand.


R-Value is a measure of thermal resistance. The higher the number for an R-value the greater the insulation. In America R-value is measured in square feet fahrenheit hours per British Thermal Unit (ft2 F h/Btu), whereas in Europe the metric measure is square meter kelvins per watt (m2 K/W). Often an R-value is just expressed as a number and only through the magnitude of the number can you deduce which unit of measurement is being used. It is best to ask the dealer or manufacturer to clarify which unit of R-value they are referring to.

Insulated Glazing or Double Glazing

When multiple panes of glass are lined up with gaps between them in a frame they are called double or triple glazed units in the UK or insulated glass units (IGU). By placing a space between the panes of glass a number of benefits are achieved. Firstly, the air between the panes act as insulation meaning that more heat is retained in the room. And secondly, the double or triple panes act as barriers stopping noise penetrating the room from outside and conversely stops the noise from inside escaping outside. This is particularly useful if you live next to a busy road with lots of traffic noise. More and more people are opting for triple glazing because of rising heating costs.

double glazed uPVC windows

Single Glaze Tinted and Reflective Glass

This is the alternative to double glazing or insulated glazing. The tint or reflective panes can also provide thermal insulation but the problem is that the tint darkens the glass and reduces the transparency of the window. In otherwords, you can see less through a tinted or reflective glass.

Low-E Coating

This is a coating of a microscopically thin layer of metallic oxide that is virtually invisible to the naked eye. Low-e stands for low emittance. The low-e coating reduces the flow of heat from outside into a room through a window. Low-e coatings are especially useful in hot countries where heat transference from outside to inside is a real problem. In double or insulated glass units the low-e coating is put on in such a way that much of the heat is reflected at an angle into the cool air in the space between panes of glass. There are low-e coatings suitable high, moderate and low solar gain situations. Low-e coating windows are standard if you live in the tropics or other hot areas. As with double glazing low-e coating will save you money on your energy bills.