Hey i finally got the chance to check out the treehouse, just read all the way through. Good show man, youve made me realise what decorating caulk is for

. i could do with using some of that! And i never even thought about using BNQ insulation stuff for a grow, thats a brilliant idea ill be copying
On the note of the extraction. If you were ever seriously paranoid about the heat escaping and being flur visable then i would recomend the following.
Rig the end of the extraction ducting to several 1ft lengths of hose pipe, cluster them in the end of the ducting and seal them in there with as much poking out as securably possible.
Put the end of the ducting/now hose into a tank of water. If you seal the tank up leaving an air vent covered with a coffee filter, you will end up with a tank of usable water out of it aswell
If you could ever be arsed that is, i considered doing this but im goin to build a shed ontop of my airbricks in the spring so wont need to worry about it.
Remember if it looks too simple, over-engineer the fuck out of it and glue a whistle to a coke can and find an elabourate way of attaching a clockwork mechanism. hmm im deffo stoned...
That said im working out a way to make a clockwork timed irrigation system for my greenhouse. Idea being wind it up and have a clockwork timed valve open and shut at intervals. so far ive learned alot about clocks... saw a valve for a hydrokit thats prettymuch set me on the path im going to go down.
Right ill stop rambling there, Ace growbox mate! nice to see some real graft put into it.