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?

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.

The ever evolving window detail (update attached).

I can't decide two things:

1. Should I use tape instead of sealant where the EWI render meets the window (can we simply stick it to the EPS and render over?)
2. Should I use two tapes on the inside, one to seal the window to the internal insulation (Tescon Profil) and then another around to seal against the masonry (ME404 butyl fleece tape). Or should I just use one tape, such as Pro Clima Contega PV or FC to seal against the insulation and then plaster over?

Blimey, all these expensive products - how do I manage to do without? Cd it be Design?

When I woke up this morning I guessed I'd get called on that! - get back to you once I've understood what details you guys are doing.

Yeah the airtightness layer is the internal plaster.

It's a terraced house. We're patching existing lime plaster as needed internally but on the external walls (front and rear) we've stripped all internal plaster and we're replacing it with clay plaster.

Window are already fitted.

The insulation is sealed against window with PU foam, although I can't remember how thoroughly.

I was thinking just Tescon Profil tape between window and EPS, and then clay plaster over the whole lot: tape, EPS and brick. Given that the plaster is my airtightness layer.

Can I simply clay plaster over tape, EPS and brick?