The purpose of door/wimdow frames is to allow the entry of light and air indoors. Even if the shell of a building is adequately insulated, heat can still be lost from the frames or glass of the window frames
Particularly the old window frames due to the absence of thermal break single glazing, sealing and general lack of large thermal coefficients are one of the main problems of heat loss in buildings.
The frames according to their material can be aluminum, plastic (PVC) or wood. Their glazing can be double or triple with various gap spaces, filled with various gases and coated with various membranes.
