Well, the very simple answer to this is NO, not really - IF, of course used properly and handled with care.
...it’s worth to understand it and see how likely or rather unlikely it is to cause the damage...
Before we started using pure water to clean windows we used to do it traditionally. Washer with soap, usually a washing up liquid, a squeegee and a cloth. Can this method damage a wooden frame? Again, the very simple answer is no, not really. However some say, a ladder can damage your lawn and the sills, as well as pushing all these soaps into the frame doesn't do any good either. So, can't win!
Ever since the water fed/pure water method has become more popular the dispute has started and there will never be an end to it. Builders/joiners used to blame decorators, decorators used to blame window cleaners. Classic finish to the story - nobody is ever guilty of anything.
So, where is the problem?
There isn’t really - firstly - the wood itself must be maintained regularly and this needs to be done properly. If this was always the case - writing this post would be a total waste of time.
Although it isn’t rocket science there are few factors to consider for an outdoor painting project, we recommend choosing your decorators wisely. (Of course we work with some local Guys and we're always happy to recommend them)
Secondly, once the paintwork started to show any signs of wear it should be redone, at least refreshed, at least the thinking of planning about it - should start... Once the wood started to rot, it should be replaced or refilled with special stuff, like resin etc, of course if possible at all.. It can’t be just repainted as when water comes inside - and it may well be from window cleaning, yes - but
what happens when it rains?
it would speed up the rotting/damaging process...
We clean windows once every 4 weeks; and it usually rains a little more often than that...
Maybe, better - let's not talk about this, we're not joiners, carpenters, decorator nor builders, so what do we know...?
Additionally, let's face it - the windows need to be cleaned regularly, this allows more natural light inside your Home, you feel better, the house feels better, the house and kerb appearance are important too. So not much choice here. They must be cleaned. (Full stop)
Some window cleaners say, we’re not really in a window cleaning business - we’re more in
keeping your windows clean, business.
To summarize, water fed pole cleaning system, is very, very safe.
The brushes have different stiffness and it is impossible to make any damage to either frame or the glass itself when as said before approached with caution.