When you compare the original windows that were in the market right up to ten years
ago and with ever increasing energy costs one cant help but see that the double glazed units are probably the most important upgrade you can make. The difference between the original windows and the current up to date windows are down to temperature management.
The aluminium and wooden framed windows that existed years ago were all single pane glass units. This as we latter learned was a big reason it was difficult to keep a home warm in the inside during the winter. The double glazed glass aloud a buffer between the warm air on the inside and the cold air outside. This helped some what but later argon gas was placed between the double glazed unit and a incredible buffer was created. This help tremendously.
A issue with windows throughout time is the ability of the sun to change the colour of the floor or furniture as well as the sun having the ability to warm up a home in the summer. Tiny metallic oxide granules are placed on the glass now days to stop radiation from entering your home.
The frame was a major change in product. Originally the frames were wood, although fairly insulated the elements tend to beat on a window frame at a fairly fast rate. The swelling of the wood tends to create leaks and air spaces. The long term solution after wooden frames was the aluminium frame. Although very strong aluminium was a terrible insulator. As energy efficiency has become more and more important the public have tended to steer away from the aluminium frame and as a result the window companies have pretty stopped making them. Vinyl which is a plastic is the most used because with steel reinforcement you can hollow out the vinyl which makes it a very energy efficient product. Vinyl only comes in white or beige in the Pacific North West for some reason. You can paint vinyl but inst recommended