Yes ... if you look closely there are drain slots machined at the bottom in the openers during construction. Rain water that is blown in drains out under the cill or if there is no cill in little slots in the front of the frame that usually have a little hood over them. If the muck in there blocks the drain slots a strong wind can force it past the gaskets and into the room. Must confess it is not often that I do bu I do. I also ensure that the under cill drain holes have not been gunked up by the moths or butterfly caterpillars or water can get into the window reveals.
Togo, do you have a method for preventing masonry bees using the external drain holes? They tend to go inside and then block up the hole behind themselves.
Firstly I would check regularly that the drainage holes are clear. An aerosol high pressure air duster spray would be a short term solution if they are blocked. Then provide a proper Masonry Bee nesting site. You can buy the "bricks" or "tubes" easily if you ask a Bing friend online.
Of course once you have cleared the bees and provided an alternative site for them to settle you would need to deter the determined interloper. It will not just buzz off. A fine gauze wire mesh over the entrance would have to be cut to size and secured. This may need a little skill and ability. I would think that you will need to " get a man in".
Thanks, Togo. Have you ever tried herding bees? Our garden is full of lovely accommodation without the need to provide hotels at the tax-payer's (that's me) expense. But they go where they like.
Barry all pvc frame profiles are designed to allow internal drainage. They are machined when the frames are made and are even behind/under the fixed panes. If the latest design profile has done away with this need then I am in need of a bit of research myself.
Thanks again, Togo. Get a man in? Gosh, that's a good idea. But he'd have to be skilled enough to cut a bit of fine mesh and dab it into position with a bit of mastic, and of course make sure it was properly placed over the hole and not to one side. Do you do foreign jobs at all? Central France, rural, minimum of twelve holes?
Haha No. I have heard them though when a swarm gets angry. Wasp nest are the "blessed" pest here. They will cause an irritation in any crack left unguarded. So I have taken care to seal mine.