Tyvek roof felt and space blanket condensation problems.

[raphowl]

I had major condensation problems in my roof, insulated with space blanket at ceiling level. I had Tyvek breathable roof membrane installed accross the roof, but in winter I still have condensation problems. My roofer put in a dry ridge and facia vents full length, but still had condensation. I got Tyvek in and then told me to remove all ventilation from the loft, and put extra insulation in any slight gaps around the esgdes of the joists, and seal loft hatch. I did all that and condensation was even worse the following winter. I had them out again, and they suggested moisture was getting into the loft somewhere, but space blanket is fully breathable and is designed to let moisture through, so this was clearly complete rubbish explanation. They finally said I could still get condensation with a large cold roof space! Very unhappy. I am now looking to insulate the rafters instead to remove the 'lard cold roof space'. I don't need ventilation above the insualtion because the membrane is breathable, and this is in the specs for the membrane, but I'm still worried that I may have problems even if I do insulate the rafters. Also, does it really matter if the joists and rafters are both insulated, as otherwise I have wasted all the money on spaceblanket, although I could staple and batton into the rafters instead of putting it in the joists. Any advice appreciated, thanks.

 

[freddiemercurystwin]

Condensation is actually very easy to solve. You need to increase ventilation and/or reduce the moisture from entering your loft from the rooms below.

The ceiling does need to be properly sealed ie around light fittings, where walls meet ceilings, loft hatch , extractors etc.

How many soffit vents are fitted? Are there proper gaps between the insulation and the underside of the membrane?

It has been known for breathable membranes to be 'not so breathable' due to manufacturing errors.