Exhaust fans versus 'normal' fans? - Orchid Board

daemondamian · #1 01-03-2009, 04:20 PM

Thanks everybody for your all replies and useful information

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The typical box fans available locally are rounded ones, so I would have to had padded/filled in around them too.

As to buying the normal type of exhaust fan as normally used in greenhouses- this was my first preference but where I live (Australia, in a rural area) but there's not a greenhouse supplier business nearby

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When I do get around to getting a big proper, freestanding GH

, I will probably combine getting proper exhaust fans meant for greenhouse use when I get all the other stuff I will need- that's if I don't decide to just go with vents and/or turbine ventilator/whirly things.

I have come across some more information about air stratification which got me to thinking about air flow, humidity and venting- some people have vents opening in the roof to release the hot air.

This is a discussion where some one talks about horizontal air flow removing 'good' air with hot air staying up the top- though if you had the exhaust fan up at the highest point you would get more of the hotter air being removed I think:

OrchidSafari ARCHIVES* New Program for OrchidSafari: Greenhouse Basics

This is interesting in that I read about someone who installed a the exhaust fan on the opposite end wall to an evaporative cooler or wet wall which worked well to remove heat but also removed a fair bit of humidity.

In contradiction I've read turbine ventilators do remove humidity and are installed and used to not only remove heat in summer but to remove moisture from under the roof/ceiling or in attics.

I know some one who uses whirly birds/turbine ventilators though they have said height is really important for them to be effective- my height is not that high really?

So I ended up not going with fans for exhausting air on the opposite end wall to the cooler and instead got a 30cm turbine ventilator whirly gig thing. I also found a few more exhaust fans [for bathrooms, etc] and got one [25cm AUS $49.00. that will fit under the whirly, extracting air keeping the turbine spinning.

The exhaust fan is not on a thermostat but I figure I could just turn it off and maybe cover it in winter to stop heat escaping.

I will be placing it in/on on the roof nearer towards the highest point where hot air should rise to.

I don't know how effective it will be but with misting under the benches, the evaporative cooler and trickling water down the shadecloth/matting against the fence I'd be happy if it only reduced temps just a few degrees.
Where my masies, dracs, pleuros, oncids, miltonias etc are at the moment is a mucher small potting shed, which I kept totally closed up last summer but I did set up a hose in there to release a small spray of mist [slightly dripping] and have the evaporate cooler in there [+ fan inside circulating air around].

Despite some days with temps going past 35 degrees celcius I didn't lose or have any plants visibly suffer or have masie leaf drop except for one plant that was a newbie.

I think it was keeping the humidity up around 80-90% [+ shading] that helped

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My main concern really has been about ondontoglossums and hybrids with the cooler/cold ones like crispum, I have been told and read too that they do better if temps can be kept lower in Summer.

I will post back later on how it works out and put some

of my turbine/exhaust fan up in my Pleurothallidinae and Oncidiinae Grow House photobucket folder .

Damian.