CONDENSATION

I have recently installed a consealed fix roof to a new house, in one area of the roof only above the dormer window there is a problem with condensation running down the wall, we installed the entire roof but this is the only area that is a problem. we installed sisalation under the sheets and insulation under that between the purlins. we have opened up the roof and checked that everything under the roof has been fitted correctly, it is in an area of shade for most of the day and it is winter with alot of rain experienced recently, we thought it was a water leak under the flashings but we have redone all the waterproofing and found no fault with this. the windows on this elevation are also affected by condensation in the mornings when the house is locked up over night. I am struggling to find out why this occuring and how to stop it, the house is being handed over to the owners this week and i need it done before then. Please could someone assist as i am a bit lost as what to do to eliminate the problem.