Windows [our favourite topic of discussion] can take many forms, both in terms of the type of material used to make the frames and indeed the type of glass used to glaze them with. Out of the most common types of material – [UPVC, aluminium, wood, steel, composite] UPVC windows are by far the most popular type of window installed in the Midlands. Out of the most common types of glazing material [single, double, triple, quadruple!] – double glazing is by far the most popular choice.