Cavity wall insulation

[Jake2021]

Afternoon,

Well just as I thought id got my head around cavities and insulation I’m now not sure I have

I was under the impression that a cavity was a standard 100mm but I’ve just read that refs have changed and now it’s 150mm ? Is this right or have I miss read it ?

If it’s still 100mm standard can this be reduced to 900mm?

Basically we are planning on putting a bay window in on a dwarf wall prob starting in April when we have pp … 900mm would be perfect 150mm will cause me huge issue!
Thanks
Jake

 

[cdbe]

The cavity isn't specified, it's the U value for the wall you have to meet. If it's a small area your BC might be flexible or let you increase in another area.

 

[Jake2021]

Many thanks and merry xmas
Jake

 

[^woody^]

If you are forming a bay into an existing wall, then you should not need to follow the requirements for new walls, as it would not make any sense to have a highly insulated wall within a poorly or less insulated wall.

No worse than the existing wall around it would be the minimum, but you may like to (and be expected to) consider additional insulation. This could be say, using a better insulating block on the inner leaf, or just adding insulation to an otherwise uninsulated cavity wall.

 

[Jake2021]

Thanks woody!

 

[MJakeM]

Look at Kingspan K106 cavity board. It’s a full fill 100mm product, which compresses down to 90mm once in place and leaves a 10mm residual gap. It’s designed for 100mm cavities and allows you to hit the newer u values.