If you decide to insulate the balcony with your own hands, then you can do this, but for the start you need to carry out preparatory actions. You need to remove all the things from the balcony so that they do not interfere with insulation. Next, you should replace the windows. If you are satisfied with wooden windows, then you can simply get rid of the old layer of paint, and then apply an antiseptic and cover with several layers of a protective agent. If such windows do not suit you, then you can put metal -plastic windows.