For better or worse, we own half an old pig barn. The back wall and the end gable are limestone, about a foot thick; the front wall is a mixture of bricks and blocks. We have recently had a builder in to fit double glazed windows, vapour permeable roofing felt under the slates, plus two rooflights, and build a wall of thermal blocks against the party wall, which was just a thin bit of timber.
The building gets damp through both the stone and the brick/block walls, largely because the ground level is a good bit higher than the floor. So I'm planning to use a dimpled membrane to keep out the damp while allowing the walls to breathe and basically do their own thing when this becomes my garden office.
That leaves the roof... I've taken down an old mouldering plasterboard ceiling and the exposed rafters and joists look rather attractive, so we'd prefer to leave them exposed - definitely the joists and preferable the rafters. Which means insulating between the rafters, which I admit doesn't give us much depth.
My main question is really whether we should use batts of breathable insulation between the rafters, rather than something standard like Celotex (in either case I'd leave an air gap above the insulation and below the breathable felt). When the room is occupied, all that hot air coming from me will need to go somewhere - do I risk damaging the roof timbers with condensation? Would breathable insulation (eg sheep's wool or hemp batts) reduce that risk, or just make it potentially worse? Should I just ensure the room itself is well ventilated rather than trying to let vapour out through the roof?
(The alternative to leaving the rafters exposed of course is to insulate between them AND under them - but I guess my 'breathable or not' question remains...)
Any advice welcomed - thanks!
The building gets damp through both the stone and the brick/block walls, largely because the ground level is a good bit higher than the floor. So I'm planning to use a dimpled membrane to keep out the damp while allowing the walls to breathe and basically do their own thing when this becomes my garden office.
That leaves the roof... I've taken down an old mouldering plasterboard ceiling and the exposed rafters and joists look rather attractive, so we'd prefer to leave them exposed - definitely the joists and preferable the rafters. Which means insulating between the rafters, which I admit doesn't give us much depth.
My main question is really whether we should use batts of breathable insulation between the rafters, rather than something standard like Celotex (in either case I'd leave an air gap above the insulation and below the breathable felt). When the room is occupied, all that hot air coming from me will need to go somewhere - do I risk damaging the roof timbers with condensation? Would breathable insulation (eg sheep's wool or hemp batts) reduce that risk, or just make it potentially worse? Should I just ensure the room itself is well ventilated rather than trying to let vapour out through the roof?
(The alternative to leaving the rafters exposed of course is to insulate between them AND under them - but I guess my 'breathable or not' question remains...)
Any advice welcomed - thanks!
