Here are some updated pics of my GH: This is the west facing side. Every surface, except the window area is covered in 50% shade cloth. The two western roof vents are also visible from this angle. Full shot of the interior, just prior to rearranging some plants. I still have LOTS of free bench space for new plants! hehehe. The south window is also visible from this view. The cattleya section (One stray dendrobium anosmum is visible there also) Cattleya backbulbs in rehab: Cymbidium Alley: The vanda section is new. This is the first time I am growing vandas. There is a dedicated mister nozzle at the roof, pointed down at the vandas and other mounties. My potting bench. LOL. Assorted fruit seedlings section: Let me know what you think. I would appreciate comments and recommendations.

You want to copy the html tag, the "a href" box, for inserting a pic: Is it absolutely necessary to have roof vents? - not with an adequate exhaust fan. I actually keep my roof vents closed during most of the summer. The air movement is much better across the GH with the ridge vent closed. Remember that cuestaroble's formulas are for passive ventilation, not ventilation using an exhaust fan. Is a fan that moves 1600 cfm to powerful? - no, that is one air exhange about every 40 seconds, and that is OK. Would it disturb plants too much? - probably not if you use care as to placement. A large-leaved plant like a banana or GBOP probably would be best placed off to the side somewhere. What temp should I set it at? - depends on what you grow, but I wouldn't set it lower than the full open setting on the intakes. Maybe 75-85F. You can experiment with that. Is that the correct place to mount it? - sounds good to me. Is that enough intake for the fan? - my calculations show that your intakes are 2.5 times the area of your exhaust, which should be fine. You may want to try to increase the "fully closed" temp setting on the intakes from 40F, depending on what you grow. Will I need another smaller fan for air circulation? - yes, but not when the exhaust fan is on. Your exhuast fan will move plenty of air for HAF purposes, but when the fan is off, you may want the air to continue to move around the GH.

Well, my initial plan would probably involve heating to about 48-50 at night, maybe kicking it up to 60 during the day as a backup for days the sun doesn't warm it enough on its own. It seems there's a balancing act between having enough ventilation to keep humidity and CO2 in check, but not so ventilated you're paying to heat your entire yard. Couple more questions: 1. Regarding ventilation fans/shutters - do yours kick on in winter during cold but sunny days? How do you properly ventilate without too much cold air hitting them? My thought was could I use a hybrid system of natural venting plus a fan that kicks on at a higher temp? I know that for the shutters you can get a shutter motor to open the shutters a few degrees before the fan. However, can you do the same with the shutters on the fan itself? My thought was something like this: You have the fan high up on one side of the GH and the shutters/vents low down on the other side. At 68 degrees or so, the shutters on the low side AND the shutters that cover the fan itself up high can open up, just to let air naturally flow in a bit without too much of a cold air shock. Mostly at this point to keep CO2 and moisture levels in check. Then, if it still continues to heat up despite the small amount of ventilation that occurs, the fan can kick on if it hits 80 or so. 2. Does such a fan exist that has a seperate shutter motor and control from the fan itself?

On the contrary, as far as I know, camellias do not need a dormancy period, since they can flower in fall, winter and spring, and keeping broad leaved evergreens of most types in a not so bright area through the winter might kill them , since most older literature says they still need light even during the winter months. I've had mine indoors for years through the winter, and usually get winter or spring blooms on mine at a temperature in the seventies during the day and bright light, but they do need humidity in the winter. Just be careful with the watering as well, as they hate sitting in standing water , and I have lost a few outdoors that didn't have the water in the saucers romoved soon enough. They like moisture , but not soggy soil.