Hi, wondering if anyone here has some expertise in building that can suggest a good solution for me. I have built a 16' by 10' outbuilding at the end of my garden. Effectively it's a glorified shed, it is timber construction with a slightly sloped shed style roof, there is a patio door installed. As it was built as an outside office for my girlfriend who works from home i have gone crazy on the insulation, i lined the inside of the outer walls and ceiling with a double foil lined bubble wrap material then 100mm celotex boards inside the walls and ceiling then 8mm ply boards for the internal walls. As you would imagine it's great at holding in warmth. However now i am getting really bad condesnation inside, i understand that i need to get the moist air out and was thinking maybe i could install an electric extractor fan at the highest point inside. Was thinking perhaps an Xpelair LV100H it's a extractor with an inbuilt humidity sensor. One question would be, would i need airflow coming in to the building from another point ie down at the bottom like an air brick also. Obviously my biggest fear is to lose all the heat i've worked so hard to keep inside. Any suggestions? Thanks