IWI on walls but what to use between joists in first floor void space?

[zachmbutcher]

Hi all.

i'm getting ready to put the some insulated plasterboard on my internal walls upstairs and im just wondering about the cavity under the floor. if i use internal plasterboard down to the floorboards then there is none on the wall between the joists in the floor void and surely this will counteract the point of the IWI. what would you recommend for filling the gap along the wall? i dont plan on filling the length of the cavity just around the outside.

 

[JohnD]

Mineral wool quilt as used in lofts.

The joists are probably about 7 inches high.

You mostly need it round the edges of the room. Pack it tightly as draughts and dust mostly blow up the gap under the skirting.

You only need to do the entire floor if there is an unheated space below.

Use the brown stuff treated with Ecose, it does not shed irritant dust and fibres.