Why
? I am intrigued.
I actually got up on the roof yesterday and inspected the current metal ones.
We get a very small drip of water about twice a year if we have heavy rain so if we are not here we always leave a bucket under it. Also when we open them in the Summer if we have people stating there are no fitted screens although we have a net at each on expandable metal rods but it means people never leave them open whilst they are sleeping for fear of mosses!
One of the lights won't open as the catch has "frozen" and the other creaks when you open it!
I put sealant all around the glass yesterday but it is clear to me that they will need doing sooner rather than later - so my research phase starts now!
Remember you are talking to a man who went into a Ford dealership in the UK and after looking around my chosen model when the salesman said "when are you looking to change your car sir?" I replied 18 to 24 months.
I don't know why but he just walked awY from me and Gill said "why did you say that?" - "because it's true" I replied.
I like to consider things carefully and thoroughly whenever possible :-)