is there any way we can design this box, so that the grow room, becomes the drying room, when it comes time to harvest and dry buds?
I'm not up to this bit yet, but I plan on doing exactly that. Would like to hear from more experienced people too. It would mean 2 weeks downtime between grows cos the buds need to be in the dark
I can't comment on LEDs, hope some else can guide you there. It will still produce heat (every watt of power used generates heat in the end) but its easier to cool and you can ignore all the air-cooled hood stuff which makes your ventilation simpler.
Doer should have cleared up the confusion I caused,
-does it make sense that HID lights in a small space should be cooled with outside air through a sealed subsystem (shed or outside air>duct>fan>duct>air cooled light hood>duct out) so you clear a lot of the heat. You shouldn't get any smell in this airstream. If you only have 1.65m height you will benefit from this cos you can keep the HID lights closer to the plants than otherwise.
-the main exhaust fan has to PULL through the carbon scrubber (this is debatable but my hydro shop guy says this is the most efficient way to use a filter) so thats why we get the complicated setup to filter both spaces outake
If you get high humidity/cold temperatures (check Bureau of Meteorology past data for your area)
budget for a dehumidifier (~$350). I tried to get away without one but decided I can't risk my crop to mould. That, a few oscillating fans for circulating air, and cleanliness are the biggest things you can do to stop mould. You will never filter out ALL the mould spores. They are everywhere.
One last tip, google your local water company's annual water quality report. They publicly release testing data which could help you decide if your tap water (after you let it sit out for a bit) is good enough to use without filtering and crap. Mine is great, you want a low EC.