Debbie,
WFP not suitable for inside work, far too much water
Outside very different though, a superb tool.
One thing we do not have over here are screens, so that is hard for us Brits to picture, as you say, the market and its requirements are very different.
Calcium/limescale build up is another thing again, at the moment, so far as I know, WFP won't touch it.
You have to use a product that is going to disolve the mineral deposit first.
I do a car showroom, on some of the windows (Huge plate glass affairs) there is often a lot of 'spotting' from the guy who is washing the cars on the forecourt.
This actually irritated me intensely as it is caused by him using the hose on a spray jet setting to sluice off the suds from washing the cars.
Bearing in mind that I am there every fortnight, so any mineral deposits will only have been there a very short time, I often have to go out and scrub some of the panes with applicator and a lot of elbow grease to get rid of these mineral deposits.
If it was 12 months between cleans I dread to think what it would be like
Wouldn't be a problem if they didn't jet the water off the cars, a gentle flushing with the full flow of the water from the hose would be much better.
For high work the WFP is tops, maybe a hot water system would be better for the type of work you describe though.
Grime baked on for a year would be more readily dissolved by this method.
With such a long time between cleans, every clean is a first clean, and would therefore be hard work with standard WFP.
A company such as Ionics, who do what I think they call their 'Thermo pure' hot water system, would be able to advise you.
For any form of regular, repeat cleaning WFP is fantastic, and, safety notwithstanding, is the reason it is taking off so quickly over here now.
Perhaps you will have to come over on a 'fact finding' mission
I'm sure many of the WFP guys on the forum will happily give up some of their valuable working time to 'show you the ropes'
............sigh..........I have to say it
I think they will all be happy for you to get to grips with there poles for some real hands on experience
Sorry moderators, not meaning to lower the tone
Seriously though, these systems are in use over there, so there must be users Stateside who can give you the info you need, over here we can only really talk about our own specific conditions.
Ian