According to the regulations, from 2021 onwards, the Uw value of a vertical window must not exceed 0.9 W/(m2*K). However, it is worth mentioning that each of the two basic elements that make up a window, namely the frame and the glazing, have a different thermal transmittance. Consequently, the thermal transmittance of the glazing Ug is lower than that of the profile Uf, which makes the glazing a warmer window element. Uw is, in turn, only the resultant of the two values we mentioned.