Air permeability
Air permeability is really the determining factor in the energy efficiency of the window, and in the comfort inside buildings.
The air permeability of the envelope provides information on the unwanted air changes inside the building. Obviously, these air renovations will have a negative influence on the energy efficiency of buildings and will tend to equalise the indoor and outdoor temperature, cooling or heating the interior depending on the outdoor temperature, leading to higher heating or air conditioning costs.
According to calculations made using the provisions of the UNE-EN ISO 13790 standard, which sets out the method for calculating energy consumption for heating and cooling manually, it has been proven that by replacing old, well-maintained sliding windows with new ones, with a high air permeability classification, savings of more than 92% can be achieved in this section.
At present, almost all the windows marketed in Spain comply with the maximum classification in the air permeability test as soon as they leave the factory, but not all of them are capable of maintaining these characteristics over time, so it is important to choose a window that can guarantee that this property will be maintained over time, so it is necessary to choose windows made of a highly resistant material, with a low expansion coefficient that keeps the joint systems tight and does not degrade with the sun and the effects of the weather.
