M. Womersleys ltd. have been asked to suggest methods of insulating the roof void of the main hall, at one of the North Yorkshire Town Halls. Because of the need to inspect the back of the ornate plasterwork ceiling every 12 months, and as timbers in the roof void have previously been subject to rot, it is considered better to heat the roof void and reduce condensation within it. With these considerations in mind, we set out two-potential options for insulating the roof at rafter level. One alternative, using sheep’s wool insulation, can achieve a u value of 0.22, with the only risk of condensation being on the underside of the slates.