Cold bridge solutions

[Jilly]

Hi, I'm converting stable and there's a tricky cold bridge at the wall/floor junction. I'd be grateful for suggestions.

 

There is a step in the 2 courses of brick under the damp proof course (DPC) and the external wall insulation (EWI) only comes to the bottom of that. I have put in 100mm kingspan Kooltherm 103 which gives a calculated  U value of 0.15 W/m2 K .

 

If we put something behind the DPM we risk condensation, but it seems quite tricky to put insulation on top as it might float up during the screed pour. 

 

[dpmiller]

there should be a slip layer of polythene on top of the insulation which will carry on up, and stop any chance of flotation

[PeterW]

Use 30-40mm PIR as an upstand. Glue it in place with gun foam. 
 

You then put a slip membrane over the top of all the insulation before screeding to ensure you don’t get any between the insulation. 

[Jilly]

Oh yes, forgot to draw that in! still wondering exactly how to detail it.

[PeterW]

Lay it over before the UFH, tape it to the walls so it has a bit of slack then pour the screed (assuming liquid..?) then when it’s dry just cut back the excess. 

[SimonD]

I would also be adding plinth insulation below the EWI as you can extend that below ground to below your floor insulation.

 

Here's a detail example but for passivhaus (i.e. using insulating blockwork below dpc).

 

[Jilly]

Thank you, ahh,  this is what I thought we couldn't do, as insulating below DPC externally seems to not be done.  

 

Below the wood cladding batton there is just the two courses of brick, down to concrete external floor level.

 

So is there an insulating block product which could be stuck to the bricks which looks aesthetic or like brick/block and could be painted?  It couldn't be dug in below ground level as yours is. 

[SimonD]

1 hour ago, Jilly said:

Thank you, ahh,  this is what I thought we couldn't do, as insulating below DPC externally seems to not be done.  

 

Below the wood cladding batton there is just the two courses of brick, down to concrete external floor level.

 

So is there an insulating block product which could be stuck to the bricks which looks aesthetic or like brick/block and could be painted?  It couldn't be dug in below ground level as yours is. 

 

I suspect it's more a thing that isn't done here in the UK, mostly because the understanding and practise isn't very well developed here. It's perfectly fine to install xps or eps externally to the bricks below dpc. The example I attached isn't my design, it's just an image I sourced from a quick search. With mine, I have some parts where I go below ground, but others where I can't because the existing shallow foundations don't allow it. Instead I have eps that goes down to just above the existing foundations but there is a small amount of gravel between bottom of eps and the existing shallow foundations to allow drainage. You can get brick slips to go on the plinth, or you simply render, or even use slate as others have done here on Buildhub.