Re: Constructing a greenhouse

Doret,
I've got just over 21,000 sq ft of greenhouse space in Southern Georgia USA,
so I deal with this problem fairly regularly....

If possible, the best solution is to have outdoor shade areas where you can
move all of the plants once it gets very hot.
If not, an exhaust fan is required.  Each of my houses have 2, 1/2hp exhaust
fans.  They do not cost that much, and if possible run them off of 220....
you may need a thermostat and fan junction box.  This is essentially a lil
box to trip the fans into running when the thermostat goes off.
I also have cool-cells, which are essentially a 4inch thick corrugated fiber
that you spray water onto.  The exhaust fans pull the water into the
greenhouse which moistens and cools the house.
Unfortunatly here in Georgia the humidity is generally 90% + in the morning
and 75% at midday so the cool cells do not work as effectively as they would
in dryer climates.  I beleive you are in South Africa where I assume it is
fairly dry, so I would think these could drop the temp as much as 10degrees
F.

Let me know if there is something more specific you'd like to know.

Although I agree with Bob Needham on the use of ridge vents, this requires a
greater knowledge of construction and you would need to stay alert to the
weather changes.  I've seen many a ridge vent get blown around during a
flash storm.

Drew
Deep Roots Nursery
www.deeprootsnursery.com
----- Original Message -----
From: "Doret Vermeulen" <cfao@iway.na>
To: <ferns@hort.net>
Sent: Tuesday, September 28, 2004 8:59 AM
Subject: [ferns] Constructing a greenhouse


> Hi to all the fernies,
>
> I want to construct a new greenhouse.  But I need some help on this
subject
> as we build one but it did not work that well.  It was just a steel
> construction covered with UV plastic and again with white 100% shade
cloth.
> It worked wonders in winter but came summer I almost lost all my ferns.
It
> got to hot inside.  I left open the doors but it did not help much.  We
took
> it down.  Now we have a new corner that is part of the house it has three
> brick walls so all I need to do is put in a fourth wall and a roof and
voila
> I would have a brand new greenhouse.  It would be 3mx3m and 2m high but I
> need to know if I should put in an extractor fan to suck out the hot air.
I
> have no idea if this is the right name for the fan I am talking about.
>
> You see our summer temperatures are quite high it reaches about 38 degrees
> Celsius so with a greenhouse having only one door it is difficult to get
any
> aircirculation as there are almost no wind and if there are any wind it is
> scorching hot.
>
> If someone knows anything please help me out or even just a website where
I
> might have a look.
>
> Thanks a million
> Doret
>
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