Don't use a Carcoon but do have an Airchamber which works along similar principles. As my garage is not airtight I find that damp is drawn in by the fans when its wet/foggy outside and I get small 'puddles' on the plastic floor. With this in mind I always switch off the fans when its foggy/raining. After all, the whole point of keeping the car in the garage is to keep it dry!
