Moving Window Frames out into the EWI layer

[MikeGrahamT21]

I know people will have done this on here, and I've seen some examples before in magazines (though can't now find them for the life of me!).

 

I have a standard 1960's cavity build, and will be applying around 120mm of EPS to the outside. I could insulate the reveals, but would only get 20mm EPS in, and moving the frames out into the new insulation layer seems sensible, as it removes the cold bridge which would exist, gives more window sill space internally, and probably most important, removes the need to install any under sills to extend the sills of the windows.

 

Just having a quick think, I could use 2x3 treated timber, bolted to the brick, and fix the window into this, the timber would be wrapped in EPS as part of the insulation job. This seems like a solution which would last a long time and could take any window replacements with repeated fixing, but is it the best method? The windows are PVC but triple glazed so carry quite a bit of weight. I've heard people talking about Plywood or OSB, and presumably some sort of metal brackets to fix to the brick. Does anyone have any examples of how they've done this type of detail?

 

Thanks in advance!

 

EDIT: Just found a post on Green Building Forum about something very similar, I can now see the ply boxing would be fixed to the inside of the masonry, that makes sense how they get it to be strong enough. I wouldn't be able to do this with one window, as its already in situ, and fits the opening. Would this leave me with just the timber framing option on the outside of the wall? And if so, will it be strong enough to hold the load? (I suppose the more fixings, the stronger it will be...)

Edited October 10, 2019 by MikeGrahamT21

[Carrerahill]

I'll ask my builder, he is an EWI approved installer.

 

I can certainly understand what you are trying to do, I would want to know things like the cavity, right up to roof level, was well sealed and is not damp internally as although you will then close this cavity internally you will be bringing that cavity internally into the house envelope. I think that can be managed suitably but having seen some of the wall cavities in my house when I started the punch through for the extension in places it gave off that horrible damp masonry smell for about a month - I solved the issue causing the damp and it was water running over the inside of the sofit and running down the cavity in heavy rain - fine, it dries out, however if you then have these cavities closed internally and plastered over and that happened then you end up with damp plaster/wood and staining to decoration.

Edited October 10, 2019 by Carrerahill

[MikeGrahamT21]

7 minutes ago, Carrerahill said:

I'll ask my builder, he is an EWI approved installer.

 

I can certainly understand what you are trying to do, I would want to know things like the cavity, right up to roof level, was well sealed and is not damp internally as although you will then close this cavity internally you will be bringing that cavity internally into the house envelope. I think that can be managed suitably but having seen some of the wall cavities in my house when I started the punch through for the extension in places it gave off that horrible damp masonry smell for about a month - I solved the issue causing the damp and it was water running over the inside of the sofit and running down the cavity in heavy rain - fine, it dries out, however if you then have these cavities closed internally and plastered over and that happened then you end up with damp plaster/wood and staining to decoration.

 

Thanks that would be great.

 

Cavities are as dry as a bone, i've recently knocked through from an extension and there was no signs of damp at all, so I'm not concerned on that front, its more about the most appropriate way of moving the window frames into the EWI from a load bearing point, and clearly I can't use the ply boxing method of install.

[Carrerahill]

2 minutes ago, MikeGrahamT21 said:

 

Thanks that would be great.

 

Cavities are as dry as a bone, i've recently knocked through from an extension and there was no signs of damp at all, so I'm not concerned on that front, its more about the most appropriate way of moving the window frames into the EWI from a load bearing point, and clearly I can't use the ply boxing method of install.

Let me go and see if he is on site...

[MikeGrahamT21]

This is what i've got in mind as a potential solution, pinched this from someones blog on the web:

 

 

[Ferdinand]

 

I trust that you have run the overall numbers.

 

I have tried on about 3 different period properties, and have never managed to make EWI add up economically (installed by contractor) once I have cut the bills by the usual renovations,

 

F

Edited October 10, 2019 by Ferdinand

[MikeGrahamT21]

Its makes more sense financially to me, as I'm doing it myself, i've already done one section of the house successfully, so I'm prepared for the physical onslaught of doing the rest. If it were being done by a contractor, I think i would be concerned about throwing money away. I think you would be hard pressed to make EWI add up if you werent doing it DIY. I suppose the other sides of it is the brand new facade, and also the fact that you are protecting the fabric of the building which should mean that its going to last a lot longer than it might otherwise have, so theres hidden benefits over and above how much you would save off of your space heating bill.

 

The sq meterage in some areas for this is miniscule, which makes it very do-able and very cheap. Also wanting to refresh the facade, as the brick work on current house is in terrible condition thanks to the previous owners. The first two bits of EWI to be done on the existing property are no more than 3m2 in total, largest part is the gable end which is probably between 20 and 30m2 without measuring, but I'm hoping to do a large portion of that timber clad (planning approval pending) to cut down on rendering and brick slips. The brick slips for the entire project are estimate to cost around £700, the rest is just EPS, adhesive, trims and fixings.

 

This was my first attempt some 3 years ago:

Edited October 10, 2019 by MikeGrahamT21

[Mr Punter]

I can understand the timber at the bottom to take the weight but I would fix metal strap to the sides and the head and fix this to the brickwork.

 

I am not sure what look you are going for but I would prefer to have, say, 30mm of frame in the brick reveal and the remainder in the insulation.  This leaves you with a reasonable cill inside and out.

 

A section detail for windows is really useful.

 

How do you fix timber cladding to 120mm EPS? 200mm screws through battens?

 

Can you post pics of your progress and let us know what to look out for?

[MikeGrahamT21]

8 minutes ago, Mr Punter said:

I can understand the timber at the bottom to take the weight but I would fix metal strap to the sides and the head and fix this to the brickwork.

 

I am not sure what look you are going for but I would prefer to have, say, 30mm of frame in the brick reveal and the remainder in the insulation.  This leaves you with a reasonable cill inside and out.

 

A section detail for windows is really useful.

 

How do you fix timber cladding to 120mm EPS? 200mm screws through battens?

 

Can you post pics of your progress and let us know what to look out for?

Fixing windows with straps is an option, but at the front and rear of the property where the windows meet the fascia boards, there is no head to fix to, at present the top of the window frame is visible if you take the first row of tiles off.

 

The windows will have a 180mm sill, rather than the standard 150mm, i just prefer the look of these to be honest, and it gives a bit more room to play with. I'd probably be looking at moving the frame to the edge of the timber frame (should i go down this route), as i remember when i did the insulated reveal EWI on the above photo, it was a bit fiddly, and would have been much easier to just run straight over the window with  the board which was fixed to the wall. I think a nice deep sill inside would be nice too, and give a feeling of a very thick wall.

 

Timber cladding section of the gable, is actually into the unheated loft space, but I was planning on using some kind of timber fixed to the wall at 600mm intervals, or perhaps an i-joist to cut down on thermal bridging, and then use rockwall batts between the joists, UV stable membrane, battens and then the final finish cladding.

 

Sure will, i should start a blog really on here for it, as progress is going to be extremely slow!

[Carrerahill]

Just spoken to the builder, galvanised angle iron bolted to at sill level, window sits on this and then they use angle brackets to tie the window sides and top to the external leaf. 

 

There are also brackets you can buy but he found the angle was cheaper and stronger and easier to use - he fits it all so that the windows can be taken back out and new windows screwed into the brackets during replacement from the inside.

 

 

Edited October 10, 2019 by Carrerahill

[MikeGrahamT21]

2 minutes ago, Carrerahill said:

Just spoken to the builder, galvanised angle iron bolted to the underside of the sill, window sits on this and then they use angle brackets to tie the window sides and top to the external leaf. 

 

There are also brackets you can buy but he found the angle was cheaper and stronger and easier to use - he fits it all so that the windows can be taken back out and new windows screwed into the brackets during replacement from the inside.

 

 

Ok, thats really useful thank you. Angle iron makes perfect sense. What would the builder suggest where there is no head to fix to, only sides?

[Carrerahill]

25 minutes ago, MikeGrahamT21 said:

Ok, thats really useful thank you. Angle iron makes perfect sense. What would the builder suggest where there is no head to fix to, only sides?

 

He would span the opening with some angle - he has just shown me a piece of 50x50x2mm galv angle which has a 50x100mm plate welded to the bottom of it on each side, it has 2 slotted holes either side too. He says he would offer that up at opening height then bolt that on - he usually always uses 8-10mm resin fixings for edge protection reasons if he is doing a whole house, if just one window in a gable wall etc. then he just uses thunderbolts. 

 

 

Edited October 10, 2019 by Carrerahill

[MikeGrahamT21]

22 hours ago, Carrerahill said:

 

He would span the opening with some angle - he has just shown me a piece of 50x50x2mm galv angle which has a 50x100mm plate welded to the bottom of it on each side, it has 2 slotted holes either side too. He says he would offer that up at opening height then bolt that on - he usually always uses 8-10mm resin fixings for edge protection reasons if he is doing a whole house, if just one window in a gable wall etc. then he just uses thunderbolts. 

 

 

OK, sounds like he goes belt and braces, which is likely no bad idea, since some of the windows when done will likely weigh nearly 200kg.

 

Does he weld the plate onto the angle, or can you buy them like that?

[Carrerahill]

17 minutes ago, MikeGrahamT21 said:

OK, sounds like he goes belt and braces, which is likely no bad idea, since some of the windows when done will likely weigh nearly 200kg.

 

Does he weld the plate onto the angle, or can you buy them like that?

He is Irish! Every time he offers me a render type or roof detail or lead depths and sizes he says, "Right, do you want it the English way, the Scottish way or the Irish way?" The first time he said it I laughed and waited for the punchline! 

 

When asked the differences he usually would suggest Irish ways allows for bigger overhangs and greater ability to protect during inclement weather. I suspect the Scot's way is similarly good as our weather Zoning does require plenty of beefed up details but he is proud of his country and I like the Irish so I pick Irish. 

 

He has a local roller shutter company make the angles for him - he just calls in the opening sizes then they weld them up on galv steel and it had some Galvafroid or similar painted onto the welds. 

 

I can weld so would do the same, but, thinking about it, if you don't weld you could buy galv angle and then cut two smaller pieces and bolt them on to create the flange that would work just as well. Remember the top section really is just to give the window some linear support from wind loading and people leaning on them and opening and closing windows etc. 

Edited October 11, 2019 by Carrerahill

[Onoff]

Hasn't @oranjeboom recently done similar with his windows in ewi?

[MikeGrahamT21]

54 minutes ago, Carrerahill said:

He is Irish! Every time he offers me a render type or roof detail or lead depths and sizes he says, "Right, do you want it the English way, the Scottish way or the Irish way?" The first time he said it I laughed and waited for the punchline! 

 

When asked the differences he usually would suggest Irish ways allows for bigger overhangs and greater ability to protect during inclement weather. I suspect the Scot's way is similarly good as our weather Zoning does require plenty of beefed up details but he is proud of his country and I like the Irish so I pick Irish. 

 

He has a local roller shutter company make the angles for him - he just calls in the opening sizes then they weld them up on galv steel and it had some Galvafroid or similar painted onto the welds. 

 

I can weld so would do the same, but, thinking about it, if you don't weld you could buy galv angle and then cut two smaller pieces and bolt them on to create the flange that would work just as well. Remember the top section really is just to give the window some linear support from wind loading and people leaning on them and opening and closing windows etc. 

No comment on Irish lol

 

From reading passive house plus over the years, I don't think the Irish building trade have got a good name for doing things right, but this guy does seem to be going over and above to get it right.

 

Instead of welding onto the top of the angle, I suppose I could just buy thicker steel in the first place to give extra strength?

[MikeGrahamT21]

33 minutes ago, Onoff said:

Hasn't @oranjeboom recently done similar with his windows in ewi?

Any input greatly received ?

[Onoff]

6 minutes ago, MikeGrahamT21 said:

Any input greatly received ?

 

Here's his blog:

 

 

[Carrerahill]

35 minutes ago, MikeGrahamT21 said:

No comment on Irish lol

 

From reading passive house plus over the years, I don't think the Irish building trade have got a good name for doing things right, but this guy does seem to be going over and above to get it right.

 

Instead of welding onto the top of the angle, I suppose I could just buy thicker steel in the first place to give extra strength?

He does a good job. A very competent builder.

 

The idea behind the plate makes sense. A plate is welded so that the flat section that the window butts up again can go to the bottom - the other side of the angle sits above the opening then it's tight to get a fixing if at all possible in some instances, so the plate sits to the underside so that he can bolt them down further down the wall - this also protects block, brick and concrete from edge drilling which can blow sections off "edge protection". So where the plate is welded you end up with a "T" section.

 

 

 

 

[MikeGrahamT21]

2 hours ago, Onoff said:

 

Here's his blog:

 

 

Thanks i'll have a read

[MikeGrahamT21]

2 hours ago, Carrerahill said:

He does a good job. A very competent builder.

 

The idea behind the plate makes sense. A plate is welded so that the flat section that the window butts up again can go to the bottom - the other side of the angle sits above the opening then it's tight to get a fixing if at all possible in some instances, so the plate sits to the underside so that he can bolt them down further down the wall - this also protects block, brick and concrete from edge drilling which can blow sections off "edge protection". So where the plate is welded you end up with a "T" section.

 

 

 

 

Do you have any pictures of these in situ?

[MikeGrahamT21]

CompacFoam seems to have a lot of praise for this job, looks odd seeing the words easy to fix into, and high pull out next to the word foam. Wonder if I can get a sample from somewhere.

 

I still think the angle iron is the best option so far. Thinking fire resistance too, last thing you want in a fire is the windows falling out!

Edited October 11, 2019 by MikeGrahamT21

[Carrerahill]

15 minutes ago, MikeGrahamT21 said:

Do you have any pictures of these in situ?

No, I just literally went out to my garden and asked him - he showed me a set of galv angle sections in his van that he has had made up for gable wall he is doing next week. They looked good - I liked the simplicity yet very tough looking solution it provided. It will stick in my head this detail as I may do a couple of the "easy" walls on my house in the future and I will be DIYing the install so I now know myself what I will do - crack out the MIG and get some angle going! That reminds me I need a drum of 0.8mm wire!

 

He is not here today - maybe he will have an image I can get next week.

 

He also spoke in great detail about how the guy in 15-20 years time will want to change these windows and his method makes that totally possible. 

 

I have just had an idea myself - I would maybe weld little lugs onto the frame, so the window gets pushed out hard against the lugs, it's then fixed internally, but once it's sitting in the angles and hard against the lugs it cannot push out, and could literally just be held in by the woodwork/trim around it and a couple of suitable fixings to lock it all into place. By the time you seal them all up they are going nowhere. The windows have been installed in my extension for about 4 months with 4 screws! Including some 2.4m wide - they are not going anywhere and cannot fall out as the block work comes over about 5mm to lock them in.

 

 

 

 

Edited October 11, 2019 by Carrerahill

[MikeGrahamT21]

Cool that would be good if he does, or a pic of yours when you've done them? I'm not doing it this year, too late on to be taking windows out!

[Carrerahill]

Just now, MikeGrahamT21 said:

Cool that would be good if he does, or a pic of yours when you've done them? I'm not doing it this year, too late on to be taking windows out!

I'll see what he has.

 

I don't think I will do mine even next year to be honest. The plan is to have a year off building! Apart from some garden work and maybe a little wall or two - got to stay busy!