Good morning Eric and Bill,
Thank you for you comments, we still at the thinking stage at the moment which prompted my asking questions here,
I'm not convinced yet of which way to go, I like air for simplicity, I dislike hydronic because its power hungry with the circulation pump and fans (but does have better temperature control)
I was thinking with either system that I'd run the pipes through bulkheads well above the water line to protect the integrity.
I'd like to know if anyone had done the install and had pictures, I'll investigate also if TW3 has any obvious signs of the path that the fresh air system might have used.
Thank you both for your advice
Darren & Karen