it seems to me we are a bit slow on this in this country.... i had a client who wants his roof re-doing. and solar panels. looked at all sorts of options, solar century c12, and romag slates were too expensive, couldn't find a decent in roof system which didn't need acres of space around it. most were over priced and poor quality. in the end the most cost effective way was to just re-slate and retro fit (obviously at the same time). but you drive through austria and all their thermal is built in.
I'm buying a house which badly needs a re-roof, i'll be stripping it off working out some BIPV i quite like the look of the schletter system. but can't speak to anyone about it. failing that i'll be sorting out my own system with some elaborate drainage techniques.
it seems in austria most of the mounting kit is built bespoke by a local fabricator... you'd never be able to do that here as their is way too much focus on banging it up as cheap as possible with parts made half way accross the world, which are barely suitable, but at least they are available so we can crash it in before the next deadline!
anyway, back in topic, i'm with worcester, if i was selling a cost effective solution i'd metal trapizoidal roof it, then retro fit with direct rail or something similar. cost effective, safe, reliable, tried and tested.... if it was my own roof! well i'd have some fun with something a little more bespoke!
