Window Positioning

[LA3222]

Quick question regarding the positioning of Windows within the reveal.

 

The pic below shows where my Architect has drawn it.  From bits I have read here I was under the impression it should be mainly sat within the SIP frame, bridging slightly out over the cavity as such.

 

I am sure I've read on here that people using TF normally use 50mm pinch batten around window openings to give something to fix to once the frame is up and also ensure it is directly located as the rest of the house goes up around them at a later stage?

 

Some advice would be appreciated.

 

Ta.

 

[Alex C]

If that hatched block is a brick skin to the outside of the building, then your architect does not understand the basics of thermal bridging and insulation. There is a direct line for heat to transfer completely avoiding the insulation in the wall. You need to put the window inline with the insulation if you actually want to keep the cold out.

Edited June 15, 2019 by Alex C

[Mr Punter]

Yes, move it inward by 100-150mm.  You will also need to allow for differential movement between the frame and the blockwork, especially at upper floor level, as the frame will shrink downwards and the blockwork will not.

[LA3222]

1 hour ago, Mr Punter said:

Yes, move it inward by 100-150mm.  You will also need to allow for differential movement between the frame and the blockwork, especially at upper floor level, as the frame will shrink downwards and the blockwork will not.

Thanks, you have confirmed what I suspected needs to happen.

 

As far as frame shrinkage, it is SIP which iirc doesn't suffer from shrinkage like a timber stud does (I'm happy to be corrected if wrong!).

 

1 hour ago, Alex C said:

If that hatched block is a brick skin to the outside of the building, then your architect does not understand the basics of thermal bridging and insulation. 

 I see a lot of these kind if issues in the forum with members and their architects - it doesn t neccesarily reflect competence/knowledge - it may be haste while they carry out the other myriad jobs they have.

 

I think we tend to forget that when we commission an architect, we are probably one in a long line of customers and these things may well happy.

 

Overall I'm happy with the service.  Ultimately it is our responsibility to check/challenge where necessary hence my sanity check question to the forum.

 

Thanks

 

Jamie

[MikeSharp01]

When moving it in you need to look at the cold bridge again and make sure you take every opportunity to get insulation round the frame so there is no direct path other than those that cannot be avoided into the building. The outer cill is a place to look as it will be on the blockwork and the inner one also as you are already loosing some of the frame to the cill see if you can get some insulation in. Also when standing the frame on the interstatial insulation, as you will if you are moving the frame back, you make need some small structural rethinking. 

[Alex C]

4 hours ago, LA3222 said:

 

 

 I see a lot of these kind if issues in the forum with members and their architects - it doesn t neccesarily reflect competence/knowledge - it may be haste while they carry out the other myriad jobs they have.

 

I think we tend to forget that when we commission an architect, we are probably one in a long line of customers and these things may well happy.

 

Overall I'm happy with the service.  Ultimately it is our responsibility to check/challenge where necessary hence my sanity check question to the forum.

 

Thanks

 

Jamie

I cant agree with you there. I think it is a case of lack of understanding and the architect just doing what they have always one. Understanding and importance of thermal bridging has moved on and perhaps the continued proffessional development hasnt kept up.If you go to the effort of drawing a section you don't do it wrong because you are busy, it is because you don't know the right way to do it. It shouldnt be your job as a lay person to check an architects details, that is the whole point of employing one. I have been told by a number of architects that my house looks German because the windows are set back deep from the face of the cladding. It isn't German it is just detailed properly for a well insulated house with no thermal bridging. 

[Mr Punter]

4 hours ago, LA3222 said:

As far as frame shrinkage, it is SIP which iirc doesn't suffer from shrinkage like a timber stud does (I'm happy to be corrected if wrong!).

 

 

In timber frame it is the horizontal timber - head binders, sole plates, joists, rim beams - where the shrinkage happens. I think these still exist in SIPs.

[LA3222]

7 hours ago, MikeSharp01 said:

When moving it in you need to look at the cold bridge again and make sure you take every opportunity to get insulation round the frame so there is no direct path other than those that cannot be avoided into the building. The outer cill is a place to look as it will be on the blockwork and the inner one also as you are already loosing some of the frame to the cill see if you can get some insulation in. Also when standing the frame on the interstatial insulation, as you will if you are moving the frame back, you make need some small structural rethinking. 

In my minds eye I envisage the window sat partially on the SIP, partially in the cavity where it's attached to pinch batten.  This has insulation around it aswell.

 

I haven't spent much time in the windows thread so going to do some research.

 

Hopefully I'm thinking along the right lines!

[craig]

Thats just a lack of understanding on thermal bridging and the architect should know better. If he’s making this error, what others are being made.

Edited June 16, 2019 by craig

[jack]

12 hours ago, craig said:

Thats just a lack of understanding on thermal bridging and the architect should know better. If he’s making this error, what others are being made.

 

Exactly.

 

Our architect hadn't worked with MBC before we used him, so he contacted them to get the wall buildup details he needed.

 

He hadn't previously used the windows we specced , so he contacted the manufacturer for their recommended installation details and discussed how best to position the windows within the actual wall buildup being used.

 

Why, in this case, has an architect who clearly hasn't used a system before made assumptions (and poor ones at that) rather than seeking input from the SIPs supplier?