loft condensation Information, help, tips and advice on cavity walls, ceilings and lofts etc....

[barry james]

two years ago I fitted thick insulation between my joists in my loft and then boarded over all the joists. The condensation on the underneath of the roofing felt is very bad, so much so that there are large damp patches on the flooring when the weather is cold. There is a water tank in there and also a smaller header tank. I'm wondering if the wrong type of felt is on the roof, as I believe you can get breathable felt? Last year I fitted a large ventilator block in the wall, so there does seem to be plenty of airflo. If anyone could offer any suggestions I would be very grateful.

[david77]

two years ago I fitted thick insulation between my joists in my loft and then boarded over all the joists. The condensation on the underneath of the roofing felt is very bad, so much so that there are large damp patches on the flooring when the weather is cold. There is a water tank in there and also a smaller header tank. I'm wondering if the wrong type of felt is on the roof, as I believe you can get breathable felt? Last year I fitted a large ventilator block in the wall, so there does seem to be plenty of airflo. If anyone could offer any suggestions I would be very grateful.

Simple you have blocked the ventilation from the edges of the loft,you need to leave at lest 10 inches around all of the sides without insulation,this will not result in any heat loss from the house as this area is above the walls.