Over the last 20 or 30 years uPVC or rigid vinyl or vinyl siding windows have taken over as the most popular window type from aluminum windows. When you like at the energy savings that uPVC windows provide it is easy to understand this shift in trend. However, innovations have been made in aluminum windows and it could have argued that they are more environmentally friendly than uPVC windows.
The problem with aluminum windows is that aluminum is a metal and a good conductor and poor thermal insulator. In contrast uPVC is a plastic which provides high thermal resistance. This means that uPVC windows are good at stopping the transference of heat and cold between inside and outside a house. So in winter uPVC windows keep the heat in and cold out; and in the summer they keep the cool in and the heat out. It is estimated that just one uPVC window can save a homeowner $ 20 per winter in heating costs. Aluminum windows on the other hand, seep heat in the winter and let out the cool air in the summer.
uPVC windows are the same price as aluminum windows, can be made in all styles including patio doors, stable doors and bow windows. uPVC can be printed to look like wood or any other style. They last 35 years with minimal maintenance and are impervious to humidity.
It is easy to understand why aluminum windows became less popular. However, a few points are worth making that might make you think again about which is the better window frame type.
Firstly, the thermal resistance issue has been partially addressed by makers of aluminum windows. They now include thermal breaks that provide some insulation from outside. There is way to go but the thermal breaks will save you money in heating bills compared to aluminum windows without them.
Secondly, aluminum is a metal that tarnishes but does not rust. They will outlast uPVC windows, often they are good for up to 60 years with a minimum of maintenance. The only problem with aluminum frames is that sometimes they are easy to dent.
Thirdly, rigid vinyl windows take up more space than aluminum windows. This means that if you have French windows you lose more sunlight with uPVC frames than with aluminum frames.
And fourthly and finally, uPVC is toxic when it is produced and when it is burned it gives off dioxins which are bad for human health. This is often the case because most vinyl siding is not recycled and instead ends up in a land fill. Land fill fires are notoriously common occurrences. In contrast, aluminum is comparatively easy and straight-forward to recycle. This makes aluminum frames more environmentally friendly than uPVC window frames. As for timber frame windows without the timber has been recycled it is hard to see this alternative as the most obvious green alternative because they do not last long in bad weather and chopping trees is far from ideal.
So it is hard to decide which one is the better window type. It comes down to your personal tastes and your values.