The overall thermal performance of a window is determined by multiple factors. The first variable is double glazing or triple glazing as well as the glass thickness. Naturally, triple glazing produces better u-values. Next, the glass units have air space between the panes which is typically filled with argon gas. It has a much lower conductivity value than air, reducing heat transfer.
Each individual frame is also separated with a special non-conductive spacer, also called a warm edge. Combined with the spacer, each pane is sealed to the frame with silicone or a similar sealant. This helps prevent both heat transfer and condensation in the overall insulated glass unit (IGU).
Windows are available in several different materials, each having their own insulating properties ranging from good to very good. We offer vinyl (uPVC), wood and aluminum clad wood frames.
While aluminum normally has the poorest value, since it is only used for cladding, it still works well with wood. This results in both a tougher, more weather resistant window but also better insulation values in the IGU overall.
For modern vinyl windows, frames today are designed with multiple chambers to improve their insulating properties. Depending on the frame profile selected, the number of chambers can vary and whether or not they are additionally filled with insulating foam.
Combined with modern glass units with a low conductivity spacer, argon, a good seal and multiple glazing, you can achieve excellent thermal performance and save a good deal on heating and cooling costs in the long run.
The u-value or u-factor, measures heat insulation and is calculated for each individual component and combined for the window unit as a whole. This is then known as the heat transition coefficient. For windows, it can be broken down into three values:
Additionally values are calculated for the so-called heat bridges; these are created between the frame and the surrounding masonry and also between the individual glass panes.
The unit of measurements for these values are given in Watts per square meter and Kelvin, W/(m²K).