Initially aluminum replacement windows seemed to be a natural choice to replace the old wooden sash. But ultimately aluminum windows are not well suited for residential use. Unfortunately although aluminum is structurally very sound it also conducts cold/heath to the inside of the house causing major problems with condensation causing corrosion and mold growth. That’s where uPVC windows come in, the uPVC window material is very similar to wood as far as its thermal efficiency, but it is virtually maintenance free and will newer corrode as aluminium windows.