Fans, ceiling vs. horizontal in greenhouse

[Yourneedfulthings]

I am building a 28 ft. X 16 ft. Glasshouse and I would like opinion and/or experience regarding the better fan array.
I am considering a Big Ass fan 60" blades ceiling mount in the middle vs. few horizontal small fans along the perimeter.
I have mainly orchids and many of them are hanging.
I believe the larger fan will produce a gentle brise that ends up moving more air.
Comments please.

[silken]

I don't know which is best really. But we have a 10 x 30 ft. greenhouse. More long and narrow than yours. I used to have smaller fans sitting here and there and that was fine but they took up space and could be knocked over. We installed 3 good size ceiling fans with lights, spaced along the length of the ceiling. They are made for outdoor use and I like it much better. They are totally out of the way and freed up space. They have 3 speeds and I run them 7/24. If I need some lights at night, to go into the greenhouse and they come in handy. However if you hang a lot of your plants, then they might be in your way. I have a few hanging but the aluminum and Plexiglas ceiling doesn't support a lot of heavy hanging ones anyways.

[Yourneedfulthings]

Thank for sharing your experience. Can you tell me what is the blade spread of your ceiling fans?.
I was told by fan Co. For the area I have I only need one fan.

[silken]

Ours are 48 inch span. One large fan may be just fine for you since your building is more square than ours. My hubby was saying with two, you can set one to pull air upward and one to force it downward and get some convection going which I guess might have some merits

[Daethen]

I have a small 6 x 8 greenhouse. I had some small fans going last year but it seemed like it would dry things out in one place and barely give a breeze in another. My hubby put in a ceiling fan this year and I have it set to pull air up. We have it set just low enough in the peak to let the blades not hit the ceiling. It work great. My walkway is in the center and there is almost not air moving. I can keep a lighter lit. Out from there, I can have a gentle breeze up to wind. I love it and it is so much better.

[Ray]

I think the fan company is not advising with knowledge of what your goal is. In order for one fan to have sufficient effect throughout that large of a structure, the wind speed under it would likely be excessive. The idea is to provide a tumbling, "buoyant" environment, not a breeze.

In a 10 x 30 structure, I would recommend a minimum of three fans in a high-roofed structure, and maybe six would be better, if the ceiling is lower. They don't need to be huge.


Ray Barkalow
firstrays.com

[katrina]

Shouldn't fans also be laid out w/the idea that you want the heat to move out through vents? Direction planning of sorts. Meaning...for example...to pull the cooler air in and move the hot air out...vs just moving air around. If not, I would think the summer heat could really build up and then all you're doing is moving around hot air.

[Yourneedfulthings]

The greenhouse will have a full length automatic roof vent and 8 windows distributed around the perimeter.
I mainly want to move the air around the plants and make sure they dry fast enough after watering. With double glass and a part shade spot, I dont anticipate much heat build up. I just hate the noise exhaust/window fans make. The large fan is very quiet.

[silken]

Originally Posted by Ray

I think the fan company is not advising with knowledge of what your goal is. In order for one fan to have sufficient effect throughout that large of a structure, the wind speed under it would likely be excessive. The idea is to provide a tumbling, "buoyant" environment, not a breeze.

In a 10 x 30 structure, I would recommend a minimum of three fans in a high-roofed structure, and maybe six would be better, if the ceiling is lower. They don't need to be huge.


Ray Barkalow
firstrays.com

In our 10 x 30 area, the 3 fans are evenly distributed across the length and run on high, full time. The roof is not a high one and continues downward away from the house on the 30 foot side facing the yard. We also have a high power intake (on one end) and exhaust (on the opposite end) fan that cut in when temps get high. My large fans cause a gentle breeze at all times and you can see leaves on some orchids swaying in the breeze. I don't think I would want more air movement.

[tropterrarium]

Also consider fan failure and redundancy. Multiple fans will be safer, and most likely they are smaller and easier to replace.