As you know, the heat escapes from your home usually through leaky doors and windows. When building a new home is worth keep this in mind and decide on the windows of high quality, if you want to keep as much heat inside the accommodation. When you buy should pay attention to the ratio Uw, which is responsible for thermal insulation. On average, the ratio should not be higher than 0.9. However, if you want to have a window warmest this indicator should be Uw <0.7. Also pay attention to the passing air. This category lists the four classes and four is the highest. Then the air is not passed through to a home. For such windows cannot afford the inside running mechanical ventilation.