Hello. I've been told by my BCO that I must fit an extractor in my new bathroom even tho' it has a large opening window - pfffft. It'll be mounted high up over the bath which has a shower mixer tap, and he says it'll therefore need to be ELV as it's 'Zone 1'. Is this the case, or could I fit an inline mains powered fan with a short length of duct between it and the bathroom wall vent? Thanks.