My (stonebuilt) terrace house has a flat roofed outshot, built in 1979. As far as I remember, 2ins of fibreglass roll was specified for the insulation above the plasterboard ceiling. It certainly does not help the room retain any heat in winter. To avoid the mess of ripping down the plasterboard, supplementing the existing fibreglass and replastering, would it be possible/advisable to glue panels of insulation board to the underside of the ceiling to provide better insulation. If so what thickness would you recommend?
Thank you
