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livingontheland - [Livingontheland] Greenhouse?

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Subject: Healthy soil and sustainable growing

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  • From: "TradingPostPaul" <tradingpost@riseup.net>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Greenhouse?
  • Date: Thu, 15 Mar 2007 23:03:28 -0700


Barb and I got in on a hoophouse building party at a nearby farm. The deal
was, the farmer put up the money for materials and an NMSU rep from the
Alcalde experiment farm organized the work and with the help of about 20
people put up a hoophouse in one day. It was 20 x 60 with rollup sides. The
rep was experienced and worked like a demon, but privately several of us
had serious reservations about the final result.

We have months of hot days and cool nights in spring and fall, wide diurnal
swings common to high desert. For many greenhouse crops the sides will have
to be rolled up and down again every day for weeks on end. It takes three
people at once for the rollup or rolldown. Without automatic ventillation
the penalty for missing one morning or evening could be disaster. The
rollup sides aren't attached on the ends or connected airtight at the
ground, so it's easy for a cold, stiff breeze to defeat the whole purpose
of the greenhouse. The doors don't even try to fit airtight. Another
questionable aspect was the roof frame. They used 2-inch plastic tubing,
but instead of bending in a curve they joined two straight tubes with a 45
degree coupling that obviously stresses the cover film at points all along
the ridge. It's 6 ml UV film. NMSU has a construction guide at
http://cahe.nmsu.edu/pubs/_circulars/CR-606.pdf but it uses bent tubing for
roof framing rather than straight pieces joined at a ridge to stress the
cover.

I've built several home greenhouses myself, by myself, and they were
airtight with thermostat controlled attic exhaust fans for automatic
ventillation. I did wood framing with equal stress on the cover plastic in
all directions. Never had a problem.

paul tradingpost@lobo.net








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