Avoiding some thermal bridging.

Tim Robbins

Hi,

In our extension, it is a cavity wall with 100mm insulation in between the two layers of brick work. There is also a layer of sand cement going on for air tightness.

At one point, in the wall, the pillar for the I beam is aligned with the wall. This is so the I beam doesn't stick into your room. So, I am thinking, since the I beam is metal, it's a conductor so in theory this is a thermal bridge. I am thinking of using some internal insulation on this part - something really simple e.g. smallest insulated plaster board which I think is 25mm.

Now, unless you want to see a part of the wall jutting out 25mm, you'd have to run this down the all the 6M wall even though the I beam is only about 30cm max at the part causing the thermal bridge.

Also, I thought with cavity build the idea was the existing insulation in between the bricks was meant to heat the internal brick which then was like a heat radiator for your room. So I am wondering is there any point in doing this thermal bridging?

Thanks

Tim Robbins

Sorry, I was just wondering if anyone has any thoughts on this?

Or is there anything I can do to explain it better?

jack of all

Could you put up a photo, there might be easier way to conceal the issue....

Tim Robbins

1692264372956.jpg

This at a photo from the earlier stage of build. You might have to turn your head to the side there. Thanks a mill for your reply.

FJMC

Can you reduce the thickness of the external leaf at the column - say brick on edge (65mm) tied to blockwork either side of the column with ss mesh - blockwork tied back to column if required - then continue with some insulation (and dpc) around the column.

Your insulated dry-lining for the whole wall also works.

Blockwork will give you a thermal mass but not sure I'd say it acts like a radiator - like say a heated floor.

You will probably have enough thermal mass in the house regardless of this small section of wall with internal insulation.

Column in external wall / cavity should ideally have some protection.

F

Mellor

This should have been detailed before it was constructed. Column is placed in a vert poor location, as is a thermal bridge as you suspected. It's not as simple as insulating over the whole wall as that could introduce other issues.

Tim Robbins

https://www.boards.ie/discussion/comment/120993638#Comment_120993638

What other issues?

A small bit of thermal bridging in a house is probably not going to be a big problem - so I am wondering now could the medicine be worse than the problem. The room is about 45 square metres with 100mm insulation in wall and 150 in ceiling.

Tim Robbins

https://www.boards.ie/discussion/comment/120991156#Comment_120991156

When you say: 'Column in external wall / cavity should ideally have some protection?" what do you mean?

FJMC

My understanding is that it is generally recommended that steelwork in external walls should be galvanized.

Failing that, if the steel is in contact with the external leaf it could be protected with a vertical dpc or a coat of bitumen, etc.

Steelwork rising from the foundations is often protected with a coat(s) of bitumen paint at low level.

F