The control of condensation in roof spaces whilst achieving the Building Regulations requirement for a U-value of 0.16 W/sq m/K is discussed. Breathable sarking membranes permit the escape of water vapour, so preventing condensation in roofs with no designed ventilation. To ensure air-tightness, the membranes must have no microporosity and be self-sealing around nail penetrations. Considerable thicknesses of conventional fibre insulation may be required, and the associated installation difficulties may result in areas of over- or under-insulation. Fibre insulation requirements may be reduced by using insulated plasterboard to form the ceiling under the loft. The insulation products offered by Kingspan Insulation are briefly described.