A converted loft in a Flamstead farmhouse that was cold and draughty. The insulation was only half the answer.
Flexible Rockwool batts went in between the rafters across the loft ceiling and roof. Over them went the Pro Clima airtight system, Intello Plus vapour control membrane taped at every lap and junction with Tescon Vana. The membrane is what stops the draughts; the batts are what stop the heat.

Flamstead farmhouse, before insulation

Loft before insulation works

Loft before insulation installed

Loft before insulation installed

Flexible Rockwool batts installed between rafters in loft area

Flexible Rockwool batts installed between rafters in loft ceiling and roof

Installation of Pro Clima airtight system, Intello Plus vapour control membrane taped with Tescon Vana tapes

Installation of Pro Clima airtight system, Intello Plus vapour control membrane taped with Tescon Vana tapes

Installation of Pro Clima airtight system, Intello Plus vapour control membrane taped with Tescon Vana tapes

Installation of Pro Clima airtight system, Intello Plus vapour control membrane taped with Tescon Vana tapes
If your loft room is cold and draughty despite having insulation in it, the missing layer is usually the airtight one.