Cavity wall air gap

[Bedwyr]

Hi, I have just taken down my conservtory which was built on top of a cavity wall which has an 80mm cavity. Currently the cavity has a 25mm PIR board, but due to the new building regs I was thinking of upgrading this to 50mm PIR to get closer to the U-Values.

Would a 30mm air gap be sufficient?

I will also install insulated plasteroard intenally to reach the U-values but thought that upgrading the insulation in the cavity, I'd lose less of the room.

Thanks in advance

 

[Bob Rathbone]

Retro fitting cavity wall insulation may be difficult due to the position of wall ties, but as this is a low wall you may be able to push insulation board down vertically between the ties.