That's a lot of Joists....like A LOT!

[andy]

On 25/05/2021 at 17:50, Mr Punter said:

You could blow in thermal insulation - either fibre or polystyrene.  If you do the latter you will not be able to have PVC cables in that zone.

Remember if you insulate you need to uprate any electrical cables that run in there as well.  Warmcell would be a good option but not sure how viable it is if you are only doing a few infills (from an installer/cost perspective).