Thermal insulation

The value of thermal insulation is indicated by means of a U-value, formerly a'k' coefficient; the lower the U-value, the better the insulation and the lower the energy consumption for heating. The U coefficient expresses the quantity of heat in Watt passing through a surface of 1 m² for 1 second and for a temperature difference of 1 degree Kelvin between the 2 sides, i.e. the unit W/m²k

a single glazed window has a coefficient of 4.0 W/m²k
an old double glazed window has a coefficient of 2.7 W/m²k
a new double glazed window offers a coefficient of 1.1 to 1.3 W/m²k
a new triple glazed window offers a coefficient of 0.8 to 1.0 W/m²k

It is difficult to do better for the moment at an affordable price. There are vacuum glasses or quadruple glazing, but the technology has sought to improve the energy gain (coefficient g) of the glasses to gain the most solar heat. The best combination is a triple glass of 0.7 W/m²k with a coefficient g = 62%, classified "A" in the Energy labels