With a double glazed window, you have two panels of glass that are fitted in the same frame. They will be kept apart by a small space that will be filled in with air or some form of non-toxic gas called argon. The most efficiency is got out of these windows when they are kept apart by around 20mm.
There are numerous benefits to double glazed windows and the most important one is that of insulation that it provides you. In the winters it keeps the heat indoors and you will find that the panel that faces inside the home is of room temperature. So you no longer will have people sitting close to the window and freezing. Double glazed windows work perfectly when you have the convection form of heating process in your home. In the summers, these windows work in the reverse form, keeping heat from entering your home. In the long run you will notice that the cost of your heating and cooling of the house will come down.
If you happen to live on a rather busy street, then you will find that these glazed windows will bring down the ambient noise and give you some peace and quiet in the house. If you are in the process of replacing windows and are concerned about getting some to match your current window dimensions, then dont be. There are several glazed windows in numerous dimensions to suit your requirement.
What you have to keep in mind is that double glazed windows are an expensive amenity to have if you are installing them for the first time. However, you will be able to recover this expense in a short time in the form of lowered heating and cooling bills. The get the most benefit out of your windows, you will have to plan them for the windows that face north. The shading has to be perfect in order to give you the best protection from the sun. Get a professional to look into setting you up with double glazed windows.