Concrete lintels vs steel box lintels

[gravelrash]

masonry walls, 200mm cavity with 3m opening and deciding on split lintel for inner cavity wall... which would be most thermally efficient, concrete or steel box? anyone with experience?

[PeterW]

Insulated steel box would be preferable. 

[Moonshine]

35 minutes ago, PeterW said:

Insulated steel box would be preferable. 

 

Edit: ignore me.

Edited March 12, 2021 by Moonshine

[gravelrash]

split/ separate lintels

[joe90]

For our bifolds I used separate  concrete lintels for each skin and have a 200mm cavity. Because ours is brick built i cut bricks into slips and stuck them on the outside to match.

[Oz07]

1 hour ago, joe90 said:

For our bifolds I used separate  concrete lintels for each skin and have a 200mm cavity. Because ours is brick built i cut bricks into slips and stuck them on the outside to match.

What length were these?

[joe90]

58 minutes ago, Oz07 said:

What length were these?

3meters

[gravelrash]

Joe90# Did you access the various lintels for u values before deciding on concrete?