As in, I finally got a fan and fitted some ducting and turned it all on- and to my amazement it actually circulates through the system and out the other side! I put the base in almost 3 years ago, so it is fantastic to see that my perforated pipes didn't fill with sand, that the ends of the pipes stayed in the manifolds (blue barrels), etc!
So the system is an RVK fan, 6 inch pvc ducting to a plenum made from a 205litre blue barrel. Then 80mm corrugated and perforated pipe underground- there's 6 pipes on 3 different levels. They go into another blue barrel, which then has a short piece of 6 inch ducting again, and a Y-piece as an outlet. Inlets and outlets have insect screening on! The inlet is up by the peak, and the outlet low down at the opposite end of the greenhouse.
Comparing two broadly similar days (weather-wise). Last week (no fan) with all the windows and door open- the greenhouse hit 40C. With the fan on today it hit 28C. Output air is significantly cooler than the input. Very humid in there at the moment- I'm hoping the SCHS will dry it out slightly but the fan has only been on one day so far!
Unfortunately the peak is only 2.5m tall so I haven't got room for a banana. 2.5m is the limit here without having planning permission (which would have confused the planners utterly, and cost me £600)
Have yet to see if these things will all survive winter (the fig and lemon survived in my old non-heatsink greenhouse so they should be fine!)
Citrus are surprisingly hard work Mike! I've got a lime too and they both got chlorosis last year. This years new leaves are looking a lot better though. They're only tiny little plants in pots.
The main green plants in there are tomatoes! They look like they're taking over the world.. a bit overfertilized with all the compost I put into the beds I think! And the dwarf sunflowers that reach the ceiling...
There's also an apricot, a peach (with an awful case of spider mites), a pomegranate, chillis, cucumbers and a melon plant (which is a bit squashed by the 'container tomato' taking up over a square metre). Underplanted with violas and marigolds (tagetes). Its amazing how fast you can fill up your 'big' greenhouse!