Unfelted Roof Space Blanket Insulation getting damp on top and sides

[swebb99]

Hi I have recently boarded out the floor of my roof which is in a 1930's house with no felt lining. Under the boarding I laid 100mm of insulation and ran the boarding up to about 10-20cm away from the roof. Initially I left the loft like that and all was fine.

Recently I added 270mm of Green Space blanked insulation again leaving a space around the edges of the roof.

I went up in to the loft the other night and noticed that there were a few spots on the space blankets where what appeared to be condensation had built up under the green polythene lining. The lining on inspection has very small pin prick holes all over it. I checked and the top bits of the insulation in the blanket was wet but the bottom of the blankets were dry. I checked for leaks and signed of damp under the tiles where the blankets were damp and found none. The air in the roof seem to be flowing well as there was a fair cold breeze flowing through the roof. The wood floor showed no signs of damp or any water spots.

Any idea what the problem could be. I was wondering if maybe the recent cold nights were causing the wrapping around the insulation to pick up damp in the air and it is getting in the small holes but it is harder for it to get out, or maybe something else is wrong which I'm not aware of. Some bits of the insulation wrapping I had previously had to rip to allow the insulation to wrap around beams and so forth, the insulation not wrapped seemed totally dry.

Thanks in advance

 

[vinn]

There are endless recent threads on this subject on this forum - search for them - there's one below in the Similar Threads section.

 

[swebb99]

There are endless recent threads on this subject on this forum - search for them - there's one below in the Similar Threads section.

Yes and I spent a good hour or so going through as many as I could find before I posted. Nearly all were about issues with no gaps around the flooring, or people who had put coverings between the roofing rafters ........

My issue is I have floored out and insulated as seems to be recommended in the forums, I have no felting under the roof. My insulation is in blankets, plastic bags in effect, called Space Blankets. The surface of the top of these bags seems to be collecting moisture and some is making it's way in to the insulation via micro pores in the plastic. There is plenty of air flow through the roof (tiles). Has anyone come across this issue before, is it due to condensation due to the recent cold weather or is it something more serious I should be aware of.

Thanks