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R value for 400mm solid brick wall

Posted: Fri Apr 14, 2023 8:32 pm
by Jenna3108
Hoping someone can help me as there doesn't seem to be anything consistent online.

I live in a Victorian property built around 1890 and my flat is in the top floor. I'm removing the lath and plaster from external walls and want to add insulated plasterboard. I'm ready to make my building notice application but I am still unsure what thickness of insulated plasterboard I require to hit a U value of 0.3.

I have taken the walls in the lounge back to brick and the measurement from the exposed brick to the front of the house is 400mm - because of the period it was built and pattern of the brick, I presume it's a solid wall. No calculators online seem to allow for a wall this thick to work out the R value. The generic answers also seem to vary. I read in a few places that the r value of brick is 0.2 per inch but is that correct? That would make the current r value of my wall 3.14 - it would be nice as I can get thinner insulated boards but I don't feel confident enough in that using that calculation.

Apologies if anything I have said above is incredibly stupid but I am learning as I go with all of this.

Thanks in advance!