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Posted

Was thinking about fixing a plastic 50x50x6mm angle bracket to the inner side of the outer leaf to support the window boxes. I know @Iceverge cantileverd his osb "box" but 300mm is a lot(in our case). Anyone with a 300mm cavity done this or suggest something better.

Posted

Our windows rested on the external concrete cill and were bolted to the outer leaf. 

 

Our 18mm OSB boxes didn't actually take any weight of the window but are quite strong so long as the window isn't too wide. 

 

I'd be slightly weary of having a cold metal bracket on the external leaf connecting to plywood. It'd be inviting condensation on the ply in my mind. 

 

 

Posted
16 hours ago, Iceverge said:

Our windows rested on the external concrete cill and were bolted to the outer leaf. 

 

Our 18mm OSB boxes didn't actually take any weight of the window but are quite strong so long as the window isn't too wide. 

 

I'd be slightly weary of having a cold metal bracket on the external leaf connecting to plywood. It'd be inviting condensation on the ply in my mind. 

 

 

Re. metal bracket, that's why I was suggesting a plastic one, nylon could also do but would the condensation still be an issue? 

Posted
4 hours ago, SteamyTea said:

Make a T bream out of OSB. 

A decent adhesive, two battens either side of the T's "leg" should make it very sturdy.

Sorry for crude drawing, but is this correct

20230610_160254.jpg

Posted
3 hours ago, Oz07 said:

where's the window?

Good Question, didn't feel the need to draw, just drawing what I thought steamy meant.

Posted

I am thinking of fixing the windows to the boxes with the outer face slightly proud of the box butting up to the inner face of the outer leaf,(a strip of compriband foam between the two) hence the need for a bracket of some description to take the weight. Or is this a bad idea?

Posted
8 hours ago, JackofAll said:

Re. metal bracket, that's why I was suggesting a plastic one, nylon could also do but would the condensation still be an issue? 

 

Should work fine if the nylon is strong enough. 

 

Green building store used compacfoam. 

 

 

image.png.ec46f5e219859f288a5eac54d16877a5.png

 

https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/

 

 

What kind of windows are you using?

 

The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. 

 

 

Posted
7 hours ago, Iceverge said:

 

Should work fine if the nylon is strong enough. 

 

Green building store used compacfoam. 

 

 

image.png.ec46f5e219859f288a5eac54d16877a5.png

 

https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/

 

 

What kind of windows are you using?

 

The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. 

 

 

Thanks @ Iceverge obviously never thought of compacfoam. Will check out price difference between  nylon/compacfoam.Using internorm KF410 upvc aluclad.

Posted
On 11/06/2023 at 00:56, Iceverge said:

 

Should work fine if the nylon is strong enough. 

 

Green building store used compacfoam. 

 

 

image.png.ec46f5e219859f288a5eac54d16877a5.png

 

https://www.greenbuildingstore.co.uk/kirkburton-passivhaus-strategy-for-windows-overheating/

 

 

What kind of windows are you using?

 

The worst heat loss in our house is through the window frames. I would have liked to have overinsulated the frames if I could have easily done so. 

 

 

@Iceverge just noticed the ply box header does not span the full distance of the cavity,cavider why? Also am I correct in saying that there's a gap between the stone bed connector and the face of the window? Unsure why the didn't use joint sealing tape in same gap. 

Posted
48 minutes ago, JackofAll said:

just noticed the ply box header does not span the full distance of the cavity,cavider why?

 

Defo not. The outside leaf will be cold and possibly wet for much of the year. Any ply here wouldn't last the battle. 

 

I'm not sure about the gap there. 

 

 

  • Thanks 1
Posted
On 09/06/2023 at 23:03, JackofAll said:

Was thinking about fixing a plastic 50x50x6mm angle bracket to the inner side of the outer leaf to support the window boxes. I know @Iceverge cantileverd his osb "box" but 300mm is a lot(in our case). Anyone with a 300mm cavity done this or suggest something better.

We built a 250mm cavity 11 years ago 

 

you will need to think about moisture update in the outter leave - it sits at ambient temp and acts as thought its  single skin wall sitting in a field - we are currently investigation cracking which we think is due to freezthaw of a moisure rich external wall 

Posted (edited)
On 19/06/2023 at 06:09, fclauson said:

We built a 250mm cavity 11 years ago 

 

you will need to think about moisture update in the outter leave - it sits at ambient temp and acts as thought its  single skin wall sitting in a field - we are currently investigation cracking which we think is due to freezthaw of a moisure rich external wall 

Surely the same could be said for any twin leaf wall, be it 100mm or 300mm cavity as the outer leaf will always be exposed ambient temp from the inside. Is the crack through the block or in the plaster?

Edited by JackofAll
Posted

True - but (and I am still researching) passive /low energy homes might be more prone than those where there is some heat coming from the inside 

will come back when and if I find more detail on this 

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