Window characteristics that need to be considered
The opening is the most dynamic part of the building's outer envelope, which simultaneously acts as a receiver that lets solar energy into the space and as protection against external influences and heat losses. Aesthetically, aluminum windows are thinner and more elegant, can easily be shaped into different sizes and forms and are available in almost all shades and colours.
The total losses through the windows amount to 50% of the heat losses of the building, they are usually ten times higher than those through the walls, so it is clear how important the energy efficiency of the opening is in the total energy requirements of the building.
Special attention needs to be addressed to the following:
- Multilayered glazing,
- Instead of air as an insulator, the space between the panes can be filled with inert argon gas, which increases the efficiency of the window,
- Low-e coating which prevents loss of heat,
- Heat losses occur both through the glass and through the window frame,
- Total heat transfer coefficient Uw <1.4 W / m2K.
From the requirement to reduce energy losses, through exterior walls, windows and doors, FEAL has developed a whole range of energy efficient systems: Termo 85, Termo 85 PA, Termo 75 DA, Inowa, Termo 150, Termo 200 DA.
European legislation prescribes lower and lower values and today they usually range in the range Uw = 1.4-1.8 W / m2K, and even lower Uw <1.4 W / m2K is recommended. Modern objects require the conditions of the so-called passive houses where this coefficient is Uw ≤ 0.80 W / m2K. Window profiles also participate in the total heat losses through windows, which, regardless of the type of material from which they are built, must ensure: good sealing, a thermal break in the profile, easy opening and low heat transfer coefficient.
