Thanks for all your replies, It would seem that condensation is now the least of my worries, when the Lone Ranger and Tonto decided to add an extension onto my 1890's cottage they neglected to follow any basic rules, consequently I have now discovered that the roof slates do not overhang the roof, the extension has a large crack where it ajoins the older part of the house and all the guttering slopes inwards causing the rain to seep into various parts of my granite constructed home! It would seem the perfect solution to pull the house down and start again. To add more woes there are numerous cracks in the chimney which also let in water. Kew gardens has nothing on this house. Can anyone suggest a solution to my extension problem. No sarcastic suggestions please!! This cottage is an end of terrace on Dartmoor if it's any help.