How 'thin' can i make an external cavity wall and still meet the expected U rating of .28?
The reason I ask is that the current side wall of my house is only 23cm thick so when the extension goes up the new wall will be about 5cm wider meaning that it will not run flush internally (I presume my neighbour won't want me taking 5cms of their garden so that my internal wall stays flush with the extension walls).
So can I make a cavity wall that is 103mm brick, fully fill a 50mm cavity with a mineral/glass/rockwool solution and have something like 100mm celcon solar blocks. I might get away with sneaking 2cms over the boundary and keep my walls internally flush?
Many thanks
The reason I ask is that the current side wall of my house is only 23cm thick so when the extension goes up the new wall will be about 5cm wider meaning that it will not run flush internally (I presume my neighbour won't want me taking 5cms of their garden so that my internal wall stays flush with the extension walls).
So can I make a cavity wall that is 103mm brick, fully fill a 50mm cavity with a mineral/glass/rockwool solution and have something like 100mm celcon solar blocks. I might get away with sneaking 2cms over the boundary and keep my walls internally flush?
Many thanks