you will likely spend a lot of time at first day and nite to check temps.....while the space heaters may keep you warm enuf at nite, the sun will want to cook your plants during the day....even in winter the temps can go up in a hurry in a small greenhouse so beware! 5 gallon buckets of water under the benches will help regulate the temp at nite, they will heat up during the day and gradually lose heat at nite....if you use gravels for a flooring it will assist with temp control also as well as humidity....misting system is a necessity, but be careful of the heaters, water and elec do not mix! ventilation is still very much needed in the winter months, so probly two fans for your size gh as well as an exhaust fan and intake shutter....automate everything you can to save your time....gl and enjoy!
Mistking
Looking for a misting system? Look no further. Automated misting systems from MistKing are used by multitude of plant enthusiasts and are perfect for Orchids. Systems feature run dry pumps, ZipDrip valve, adjustable black nozzles, per second control! Automatically mist one growing shelf or a greenhouse full of Orchids.