"F" news@nowhere wrote in message
o.uk...

We've got one of the energy companies coming to my father's house to
survey for free loft insulation. Anyone know how deep it should be when
they've finished?

It is as deep as what they said it would be. Have the insulation as deep as
possible. A minimum of 12" - put more in.

To use the loft. Fill with Rockwool up to joist level. Then fit 4"
minimum, high performing rigid foam insulation over, then boards over that.
Costs more, with a usable loft area.