Plasterboard insulation

[Karl480]

I have removed some of the plaster on an external non cavity wall back to the brickwork. Had to do this to remove tiles that were cemented to the wall. Following a building control inspection I have been told that as I have removed over 50% of the plaster I need to insulate the wall to try to achieve a U-value of 0.28 W/m2K.
What thickness thermal board would be required to achieve such a value?

 

[Alastairreid]

http://www.diynot.com/forums/viewtopic.php?p=1352188

 

[tony1851]

This is another example of the nonesense dished out by the typical building inspector.

First off, when renovating an existing wall, the target U-value is 0.3, not 0.28 - there is a difference. To achieve this, you need something like Kooltherm K17 board 72.5mm thick.

Secondly, you only renovate a wall to that standard if it is 'technically and functionally feasible'. For example, if it is already a small room, and the thickness of insulation will reduce the useable space by more than 5%, you can argue the toss and get a thinner board. Is it a bathroom, or a small kitchen where the net floor space is tight?

Also remember that if you highly-insulate the external wall, there will be a cold bridge where any internal brick wall meets the external wall, and you may get condensation and mould there.

If it's not convenient to use that thickness, don't take it lying down.