Help needed to remove/reduce major cold bridge in door threshold design

[JohnW]

This door threshold detail provided by our Architect appears to have a major cold bridge in the form of the pre-cast concrete threshold. 

Can anyone suggest an amendment to the detail to remove/reduce the cold bridge?

 

Thanks

John

[Declan52]

Must be one hell of a door if it needs a 9x9 inch concrete head  to carry it!!!

How wide is the span???

If you have to use a concrete head then you move it forward so the back side is level with the inside of the door. You can then use 50mm or even 75mm of your perimeter insulation against the head. You will still have some heat loss through the bottom of the frame that sits on the head. How much depends on your quality of Windows you pick and how wide the span is. Then it's a question of can you live with that amount of heat loss. 

You will also need to knock the top block off on the inside skin so your insulation carries over the cavity to the door.

 

[MikeSharp01]

Replace the top of the threshold with a fibre glass box section filled with expanding foam. This should take the load not already taken by the horizontal side fixings on the frame. Think GBS did this and we are using the same approach on our build.

[Vijay]

Would you be able to use one of these? http://www.marmox.co.uk/products/thermoblock

[craig]

Compacfoam will do the job.

[oranjeboom]

18 minutes ago, Vijay said:

Would you be able to use one of these? http://www.marmox.co.uk/products/thermoblock

That's what some of my doors will be sitting on. Slab insulation up against it together with some perimeter upstand insulation. 

Edited August 22, 2017 by oranjeboom
Photo

[JohnW]

2 hours ago, Declan52 said:

Must be one hell of a door if it needs a 9x9 inch concrete head  to carry it!!!

How wide is the span???

If you have to use a concrete head then you move it forward so the back side is level with the inside of the door. You can then use 50mm or even 75mm of your perimeter insulation against the head. You will still have some heat loss through the bottom of the frame that sits on the head. How much depends on your quality of Windows you pick and how wide the span is. Then it's a question of can you live with that amount of heat loss. 

You will also need to knock the top block off on the inside skin so your insulation carries over the cavity to the door.

 

 

Thanks @Declan52, it's a big slider 2400mm tall by 5635mm wide.

[JohnW]

2 hours ago, MikeSharp01 said:

Replace the top of the threshold with a fibre glass box section filled with expanding foam. This should take the load not already taken by the horizontal side fixings on the frame. Think GBS did this and we are using the same approach on our build.

Thanks @MikeSharp01, I assume Building Control are happy with this approach?

[MikeSharp01]

Can't see why they wouldn't will see if I can dig out the GB'S ref.

[JohnW]

2 hours ago, Vijay said:

Would you be able to use one of these? http://www.marmox.co.uk/products/thermoblock

Thanks @Vijay, that looks interesting. Someone else suggested a similar approach using a different product Foamglas. Have any of you heard or used it? 

[JohnW]

2 hours ago, craig said:

Compacfoam will do the job.

Thanks @craig

[JohnW]

2 hours ago, oranjeboom said:

That's what some of my doors will be sitting on. Slab insulation up against it together with some perimeter upstand insulation. 

Thanks @oranjeboom, good to know someone else is using this approach. What thickness is your thermoblock?

[oranjeboom]

8 hours ago, JohnW said:

Thanks @oranjeboom, good to know someone else is using this approach. What thickness is your thermoblock?

 

 

8 hours ago, JohnW said:

Thanks @Vijay, that looks interesting. Someone else suggested a similar approach using a different product Foamglas. Have any of you heard or used it? 

If you look carefully in the pic above, you'll see that's a Foamglas (Perinsul) block. The one above is either around 65 or 100mm high. I've also used Marmox blocks for my SIP foundation walls and they are either 50 or 60mm high. I had to drive to the continent where the blocks vary in width a bit to the ones that were available here in the UK. And you can't stack them on top of each other like a normal brick i.e. one course only.

 

http://marmox.com/products/61.pdf

 

Not fitted my doors yet, but the intention is to screw through the blocks and into the brickwork below.

[Vijay]

10 hours ago, JohnW said:

Thanks @Vijay, that looks interesting. Someone else suggested a similar approach using a different product Foamglas. Have any of you heard or used it? 

 

I tried contacting them many times but they were useless at getting back to me and then gave me dead email address - strange way to do business!

[oranjeboom]

Just now, Vijay said:

 

I tried contacting them many times but they were useless at getting back to me and then gave me dead email address - strange way to do business!

I have a contact at Foamglas (given to me by someone on here I think) if anyone needs it. I did have a nightmare getting hold of the correctly sized Marmox blocks thanks to Jewson's ineptitude. But who needs the business from a self builder???

[Declan52]

11 hours ago, JohnW said:

 

Thanks @Declan52, it's a big slider 2400mm tall by 5635mm wide.

That's a big door!!!

[Vijay]

2 hours ago, oranjeboom said:

I have a contact at Foamglas (given to me by someone on here I think) if anyone needs it. I did have a nightmare getting hold of the correctly sized Marmox blocks thanks to Jewson's ineptitude. But who needs the business from a self builder???

 

Not Clive Lindsay is it?

[oranjeboom]

2 hours ago, Vijay said:

 

Not Clive Lindsay is it?

Andrew Jones.

[Cambs]

Green Building Store do something called CompacFoam which may be suitable.  Prices shown on this page (not cheap!) and also some installation diagrams showing how they've used it in thresholds.

 

https://www.greenbuildingstore.co.uk/products/compacfoam-200/

Edited August 23, 2017 by Cambs