Being a poor conductor of heat, uPVC window neither retains nor transfers heat indoors. Aluminium does both. The U-Value of UPVC is far less than Aluminium. Duroplast uPVC windows possess great energy saving potential. Window profiles have been designed with multi-chambers and double gasket sealing reduces transfer of heat .further windows and doors fitted with double insulated glass, make the window more energy efficient and saves energy by 30% - 35%.