New loft flooring insulation with insulated roof felt

Insulation in the rafters, as opposed to being fitted between the joists/ceiling, in effect causes your roof space to be a 'warm space'. The heat from the living quarters will enter the roof space, and be retained by the insulation in the rafters. In most peoples' circumstances there's no point in their loft being a 'warm space', and hence insulation is fitted to the ceiling to retain the heat within the living quarters, making your roof space a 'cold space'. Without knowing what type of insulation is fitted to your rafters I can't comment on its efficiency. Another factor that may come into play when you're deciding what action to take is ventilation. Condensation is a common problem in roof spaces during the winter months as the warm moist air we create in our homes makes contact with the cold surfaces of the felt.