How common is it? Whats the best solution?
It cant be a new one but I can find no past threads. A year ago I had my loft insulated with 10inchs of glass wool, extending the joists up to 10inchs, and boarding out with 8*4 chipboard loose laid over 80% of the area. Ive not come to lift a few and found them to be damp on the back, in some cases, dripping and slightly mouldy. Worse under the bedrooms than the bathroom, all bedrooms used.
The house is a little damp, from three showers a morning, drying washing, etc and the reason for lifting the boards was to replace the failed bathroom fan, so atleast that now works.
Presumably some of the moisture is passing through the PB, coming up through the inslulation, and condensing on the cold floorboards, and with no real ventilation space under the boards, cant get away even though the main body of the attic is well vented.
I did consider adding a vapour barrier before putting the insulation down, but it was pointed out I didnt want it over the joists, and by the time I had cut it to go in between it was fairly compromised at best, so I didnt. Thoughts so far are
- Raise the floorboards another 2/3inchs to get a ventilated void to allow it to breath.
- Paint the ceiling below with a waterproof/nonbreathable barrier paint of some type.
- Hope the repaired bathroom fan tips the balance by keeping the house drier.
- Installs a half-house MVHR system to the first floor to reduce dampness in the house
Daniel
It cant be a new one but I can find no past threads. A year ago I had my loft insulated with 10inchs of glass wool, extending the joists up to 10inchs, and boarding out with 8*4 chipboard loose laid over 80% of the area. Ive not come to lift a few and found them to be damp on the back, in some cases, dripping and slightly mouldy. Worse under the bedrooms than the bathroom, all bedrooms used.
The house is a little damp, from three showers a morning, drying washing, etc and the reason for lifting the boards was to replace the failed bathroom fan, so atleast that now works.
Presumably some of the moisture is passing through the PB, coming up through the inslulation, and condensing on the cold floorboards, and with no real ventilation space under the boards, cant get away even though the main body of the attic is well vented.
I did consider adding a vapour barrier before putting the insulation down, but it was pointed out I didnt want it over the joists, and by the time I had cut it to go in between it was fairly compromised at best, so I didnt. Thoughts so far are
- Raise the floorboards another 2/3inchs to get a ventilated void to allow it to breath.
- Paint the ceiling below with a waterproof/nonbreathable barrier paint of some type.
- Hope the repaired bathroom fan tips the balance by keeping the house drier.
- Installs a half-house MVHR system to the first floor to reduce dampness in the house
Daniel