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Wow, that's the chapter and verse for outboarding windows then - v gd.
While you're at it, I'd be ever so interested to see the frame pushed a) entirely just outboard of the masonry i.e. corner to corner with the masonry, with that majonry jamb insulation removed (that's how I've been doing it). and b) as that corner-to-corner is prob a weak point, frame pushed yet further outboard, so say 30mm away from masonry outside face.
These wd of course require thicker EWI - but EWI reveal depth, back to window outside face, need be no more than say 1.3 x the EWI's overlap distance across outside face of frame. So if overlap is say 25, then increasing EWI reveal depth greater than 35 won't improve the numbers. Tho, with these open-in windows, overlap cd easily be 50 or even 70, so reveal depth greater than 35 wd then be worthwhile.
So here's my updated detail. We're going with Ecocontract triple-glazed timber windows, 0.9 u-value (added benefit with these windows is that we can also overlap the insulation at the sill). 1. Is it realistic to bend the straps 90 degrees like that? I want to do that in order to fit the XPS insulation snugly. 2. What screws should I spec to fix into window and into the masonry?
Any ideas on how we might protect the windows once they're installed if we don't install the insulation for a while?
Its looking much improved to the initial drawing. Why dont you fix battens on bracket height into the reveal and save yourself bending the bracket. We had the same type of windows and fitted them just under 3 years ago looking very good still. I wouldn't worry about the weather getting to them, if you seal between frame and brickwork, maybe fit a triangular piece on the head to let water run off easier. By the way I ran 50mm of insulation up against the frames, which are about 80mm thick.
Shevek; Ive just installed a window, very similar in design to yours with insulation surrounding the reveal and the window mounted itself into the insulation. I am intending on doing EWI, but probably not for at least a year yet. The only difference is that my window is flush with the wall and so i was able to use normal screws directly into the blockwork. At present the outer part looks a mess as the insulation surrounding the frame is visible and the sill is huge! But it is watertight (ish) until the new EWI is completed next year.
Its also worth thinking about replacement of frames, the frames i took out of my house were probably from 1995 ish, so maybe 18 years old. But they needed replacing, rubber seals tired and no longer effective, glazing units all failed and metal parts corroded. By plastering around the frame on the interior and also rendering and insulating over the frame on the exterior we are making changing the frame a very difficult job!