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Re: [Fwd: genetics question & greenhouse ventilation]

greenhouse ventilation
> Date: Sun, 28 Jun 1998 13:56:04 -0700
> From: "M.L. van Rooijen" <lynnvr@wxs.nl>
> To: "seeds-list@eskimo.com" <seeds-list@eskimo.com>
> 
-I am looking for some advice about greenhouse
> ventilation.  This spring, partly as an esthetic compromise, I became
> the owner of a Hall's (U.K.) hexagonal greenhouse  with a pointed
> cone-shaped roof (2.5 meter diameter, walls 2 m high, to roof-point 3
> m.).  It came with a louver window at ground level, and the announcement
> 
> that the cone roof provided excellent ventilation, although it doesn't
> open, and has only a very small opening.  In anticipation of warm days
> (which hardly every come here in Holland, but you never know!), I
> ordered a second louver window which arrived yesterday.
> Now the question:
> According to the man who delivered the window, both windows should be
> high (the pane that goes from 120 cm to 180 cm above the ground) to let
> the hot rising air out.  On the paper from Halls, stands the instruction
> 
> (with no explanation as to why) to install the window in the bottom pane
> 
> fom 0 - 60 cm above the ground (assuming one window).  My idea was to
> place one low, and the other high and on the other side, in the hope
> that cold air would be sucked in under and rise and go out above,
> creating mre circulation.  The man from the garden center sticks by his
> advice of two high.  Which choice do you think will give the beter
> ventilation?  I do realise that on 'normal' rectangular greenhouses, the
> 
> windows are high--but also placed in the slanting roof, which I cannot
> open.
> Any advice is appreciated!
> 
> Lynn van Rooijen
> Netherlands


Dear Lynn:

As a woodworker and landscaper, I've built my share of environment
control structures, both of my own design and from other's designs and
kits.  

If there's one thing I've learned with someone else's structures, it's
FOLLOW THEIR DIRECTIONS.  

While the window man probably has all the good intentions in the world,
you'll be better off listening to Hall's instructions and setting the
window in low.  Your second louvered window could be used as a back up
ventilation port if the low window in combination with the roof vent is
insufficent.  I'd place that one at mid-height...cover all the options!

More to the point, Lynn, what is this structure going to be used for?  
Are you going to install a misting system and use it as a propagation
house?  Will you be providing bottom heat via plastic or metal tubing?
Is it going to be for tropical plants and have a sophisticated
environmental control system (heaters, fans, cooling wall, adjustable
light levels via reflective/thermal blanket)?  Or is it more a simple
covered porch-like structure which will be used half the year and shut
down in winter?

Hope this hasn't created more problems than solutions, but a controlled
environment structure is a synergistic thing and everything about it
depends on everything else to create proper world for its inhabitants.
(It couldn't just be EASY, could it!)

Glen Seibert
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