Windows - Help!

[HEB1]

Having hovered over the site for the last 2 years - we now have our SIPS kit largely assembled up on the Outer Hebrides.  We are aiming for high detail on airtightness and will be cladding it in 12mm thick Cedral Click on a 50mm timber batten

 

A recurring theme I remember reading on the forum is 'windows, it's always the windows'. Following the predictable " leave it to us, don't bother with air tightness" conversation - our lovely Rehau windows are in:

 

My concerns are,

 

1. 50mm of the 70mm frame is sticking out of the cavity (although from inside they look great) 

2. Should the window cills be sitting directly on the VCL/Breather membrane in the cavity with nothing to prevent water/air ingress? - I had assumed at least a bed of silicone?

3. Our entrance doors are due to be similarly fitted this week.

4. Gaps of only 5mm on 3 sides of openings 

 

I had planned on using Compriband on the outer edge with low expansion foam on the inner  (as specified) with the windows flush with the outer edge of the cavity, I had ordered 180mm cills specifically but 150mm cills have been supplied.

 

Photos also attached below show standard practice up here to have the firestop flush with the outer edge and tight up against it for ease of cladding the reveals but is this good enough?

Gaps are squirted full of silicone.

 

Any help would be appreciated as glazing yet to be fitted in the large windows.

[Mr Punter]

It is good to have the glazing near to the centre of the insulation but not fatal if you don't.

 

It is becoming more common to have airtight tape internally, adhered to the window frame and back to the structure.  You may also have some insulation on the internal reveals to stop cold bridging through the timber.

 

Foam around the frame.

 

Compriband is good but silicone will also work.  The metal flashings and dpc at the heads is good.

[HEB1]

Many thanks for that, should the window be sitting on silicone or compriband?

[Buzz]

I have little or no idea about your window questions but , what a wonderful view you have and love the amount of glass you have to make the most of it .

[LA3222]

Stick some compriband in from the outside which will give you the watertight seal but allow vapour through. Then foam up to the compriband from inside...try not to overfill so you aren't trimming the foam too much then apply airtight tape across the window to the reveal. Should only be about 10mm on the frame which will get hidden by the plasterboard.

 

Look at the illbruck 'i3' system and you'll see how it all works together.

[HEB1]

Thank you - much appreciated!