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Explaining this thermal bridging door threshold detail?


SBMS

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The architect has designed a detail to minimise thermal bridging at our door thresholds.  We've got a 200mm cavity with EPS beads, and large sets of sliders. I asked for a detail that minimised thermal bridging, but also a detail that needed to support the weight of the bottom of the sliding doors. They didn't look at compacfoam etc because we tried to keep it as standard construction details as possible. However, I am struggling to understand, on the below, what the purpose of the "EPS Insulation supported off the bottom wall tie" is for? Does this aid in reducing bridging? Builder also can't understand how the detail reduces thermal bridning. 

 

Our sliding door track does actually have a thermal break in it as well so I might be overthinking this detail?

 

image.thumb.png.61284d6f61eb066ebdb85541d558ef2b.png

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13 minutes ago, ETC said:

VCL should be above the floor insulation.

DPM should overlap the DPC.

Build solid to underside of slab. Cavity above.

Cavity above but then what supports the door track?

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2 hours ago, ETC said:

VCL should be above the floor insulation.

DPM should overlap the DPC.

Build solid to underside of slab. Cavity above.

Do you think the EPS is actually doing anything?

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9 minutes ago, Russell griffiths said:

Eps is doing nothing

xps 500 or compac foam to form a continuous line under the door. 
the load exerted down from that door is minimal 

Thanks Russell. Can I do a row of marmox (easier to source than compacfoam) - and would it be advisable to do the full width of the cavity in marmox (two 100mm)?

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4 hours ago, SBMS said:

Thanks Russell. Can I do a row of marmox (easier to source than compacfoam) - and would it be advisable to do the full width of the cavity in marmox (two 100mm)?

I’ve never used it in a cavity wall so you will need some more details from someone with that scenario 

just follow the principle that you need to isolate the heat from the floor coming into contact with the cold blocks below the door, and the cold from outside then also damp from coming upwards and from coming inwards if you are having that flush threshold. 
the pic is different to your buildup, but highlights the two problems, keep the cold from the door and floor  IMG_1141.thumb.jpeg.8443d1fcc9bca36a639805962aab34d1.jpeg

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1 hour ago, Russell griffiths said:

I’ve never used it in a cavity wall so you will need some more details from someone with that scenario 

just follow the principle that you need to isolate the heat from the floor coming into contact with the cold blocks below the door, and the cold from outside then also damp from coming upwards and from coming inwards if you are having that flush threshold. 
the pic is different to your buildup, but highlights the two problems, keep the cold from the door and floor  IMG_1141.thumb.jpeg.8443d1fcc9bca36a639805962aab34d1.jpeg

Thanks. The marmox technical support chap said to do something similar to this:

 

image.png.5e0b454727c61dc2e6e05806d17f0b29.png

 

 

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Posted (edited)

Probably a mad idea, but is there any reason not to put superfoil under (and overlapped potentially) the track in door openings to reduce thermal bridging? By my reckoning the R value of SF60 is comparable to a thermoblock brick?

Edited by SBMS
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2 hours ago, SteamyTea said:

multifoil insulation is not effective

It depends on every shiny surface facing an air void, and reflecting energy back where it came from. As soon as it is touching a hard surface or compressed then  that supposed property is lost.

Plasterboard with a foil face was once sold on this princople but this is no longer  claimed.

 

I read that their lab tests are done their own way. 

 

I would consider multifoil or bubble wrap to take the chill or heat off an attic or outbuilding, because it would be thin and easy to pin up.

 

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