My flat has wooden pivot windows (double glazed). A few are leaking if kept open in the rain. What is the best way to seal them? It looks like some sort of putty was used in the construction, which I guess has broken down over the years. Im guessing silicone is the easiest way to go, but unsure which brand/type to use. Ive 9 windows in all to seal so I want to keep the costs down but I dont want to use anything which will need replacing in a few years. Ideas?