Foist by his own pumping!
I encountered an unexpected problem during very cold and frosty weather 2009-10 and 2010-11. Condensation collected on the back of my outside skin lintels and dripped down from above my window heads on to the window sills. I did build in a cavity tray but this tucked in above the single skin steel lintel. I cant be sure if this was moisture that was breathing its way out from the inside of the house or if it was still from initial drying out. On the ground floor it was no problem and there were no metal lintels on the first floor but in the basement a very few drips of water ran down the triple glazed units both inside and outside. Thus the title — Foist by his own pumping! I will wait til next year before taking any action on this. The problem only manifests itself when outdoor temperatures fall below -2C