The neighbor has two 40X40 (all units in feet here and after) sheets
of clear poly that he will give me, since he sees that I have tunnels
for my winter vegetables (this year I will get to harvest until end of
january at least, he actually told me as I was getting back into the
house with a paint bucket full of just picked radicchio). I just love
these hot stove projects, but before I embark in it, a question or two
for those who have built hoophouses.
1) those sheets are clearly very large. If used without cutting, they
will cover a 24X38 area, with a maximum height of 12. That is an
unusually wide hoophouse.
2) I think I want to use PVC pipes, glued with plumbing solvent. The
question is, can I make them withstand a windstorm or snowstorm. I
have seen lots of pages on the web, so I have seen what can be done.
Amongst other solutions, I noticed that there were hoophouses with
poles supporting the central beam, and of course one can always anchor
the hoops to the ground. I guess I am more concerned about the snow
than the wind.
3) I am thinking about getting a double layer of poly for extra
insulation. Any experience with that? I would need a double hoophouse.
4) I plan to make two trap doors at opposite ends, and have one set of
doors with poly and another with chicken wire. Will there be enough
ventilation with the chicken wire doors in place?
PVC works well for smaller units, but I think (guess) that this is too big for
snow. Even wind can be tough, though IMHE putting guy lines between the hoops
can make a world of difference -- there's just too much tension in the
plastic to depend on attaching to the perimeter of the material, even if the
tension is distributed by tape over a relatively broad periferal area.
You didn't say anything about where you live (e.g. frequency/magnitude
of snowfalls) nor how much spacing you might have between hoops. My guess
is -- if there's a chance of having 6" or more of wet snow, it will probably
be more stress than any reasonable PVC system could withstand.
Might you get a warm sunny day? It's incredible how much heat you can
build up in one of these. Doors might be enough if you could supplement
with a fan. How big might these trap doors be?
What about cutting the 40x40 into two 40x20's, and make 2 hoop-houses?
(Long, not wide). If the snow isn't too heavy, there might be a chance...
email@example.com (Frank Miles) wrote in message
In my present tunnels (each over a 4 ft bed) I have hoops, and I have
a central beam.
I live in Michigan. My experience is that snow will happily slide down
a hoophouse unless there is a sag. But I concur, it is probably too
I know that the poly, properly clamped, will not get loose no matter
the wind (poly clamps bought at Territorial Seeds).
Maybe 4.5 ft by 7 ft, if I have to go in with the cart full of manure.
I have already calculated that there is not enough heat storage in a
wall of water drums. The heat input is probably 50-100 W/m2 in the
winter, and the heat sink is the soil. Not clear how fast it can
absorb heat and probably depends on it being moist.I know from
experience that mulch and hoophouse is a deadly combo (plants fry, or
freeze, or both), which is a problem because all mulch must completely
decompose within the growing season (that means only leaves or
That is probably what I will do. The hoophouses will still be 6ft
high. By placing them side-to-side I can take care of half the
watering, since the water will pool in the middle, evaporate, condense
on the poly, and drip all over. It certainly works for my current
tunnels. One can even consider a sunken hoophouse (I have sandy soil,
and sunken will help with the wind), with a sloping floor so as to
redistribute the water.
On 29 Dec 2003 07:55:47 -0800, firstname.lastname@example.org (simy1) wrote:
That would be quite large. Try this link for a 12x14 foot green
house. I built one of these and have been happy with it. The width
is pretty much set by what one can do with PVC pipe, but the length is
arbitrary. One could easily make it 28 foot or longer if you have the
room. I'm planning to set up a second one. I did not do anything to
heat the house, and was picking vine ripe tomatoes on December 7th in
I modified the design a bit. Also, double check the amount of wood on
the check list for the ends of the hoop house. IIRC there was only
enough listed for One end!
some more considerations that will probably interest only backyard
1) the link above uses cattle panels (basically very strong rebar),
and (this is important) they bend them quite a bit, so the hoophouse
is taller than a semicylinder. The rebar then provides some tension to
push up against the snow, in fact they easily hang pots onto the
rebar without having the house sag. But, if you want to use the soil,
you have less area underneath. I suppose the tradeoff between tension
and surface is inevitable. Incidentally, my 11 feet PVC hoops don't do
that. After two years at most the take a permanent hoop shape. They
are still strong enough to shed snow without collapse. Rebar also
provides excellent support to the poly, effectively preventing pooling
of water or accumulation of snow.
2) when using the rebar, they have two problems. The first is that all
sorts of of rough spots will scratch and break the plastic. IMHO, this
is the perfect place where to use that old hose you have in your
garage. Slit it lengthwise and fit it over the ends. The second is
that they have trouble clamping onto the rebar. the PVC clamps are
great (amongst other things, they are capable of holding the plastic
even when the wind is blowing from the inside, such as may happen when
one leaves an opening after harvest) but alas, only come in PVC sizes
(3/4 and 1). Probably just a matter of clamping a PVC pipe to the
rebar on the inside, then clamp the poly on the pipe (that will be a
pain when one removes the poly for the summer, but safe until then.
Various other issues include anchoring the whole thing (probably
enough to bury a few cinder blocks around the perimeter, with hooks at
the surface for strapping), double layering (do the second layer
inside, it will sag, do it outside, it will sag and touch the first),
chicken wiring (when I take off the poly, I still want the rabbits out
of my garden), and how to do the ends. Nice clean design overall.
I am settled on the cattle panel hoophouse (a PVC one has too many
techincal problems which I won't mention here, though I will use PVC
pipes at the edges for the clamping of poly). One last question: the
hoophouses( two of them, each
38X12, side by side), should be oriented N-S or E-W? Light hitting the
at an angle below 40 degrees is totally reflected.
I really don't know which way would be the best-----I've seen
greenhouses around here pointing in all sorts of directions, based
mostly, I guess, on the topography of their land. Logically I would
assume that the benefits of a hoophouse would be in its use during the
winter and I think that with low sun angles that you would get the
best perpendicular angle of the suns rays with a East/West
orientation. One problem with E/W would be that the hoophouses would
have to be end to end and not side by side.
For what it's worth-------Bill
Yes and no. In Zone 6, one would use a greenhouse for, say, tomatoes,
until June 1. At that point in Ann Arbor the sun is 71 degrees over
the horizon at noon. Also in the winter one has plants that grow
during the growing season (mostly), and are kept alive for consumption
through the winter. In winter, a N-S house will have shade near the
edges on the N side. In May, it will have shade along most of the
edges. Then again this is the kind of midday shade many plants
A E-W house will have little shade in winter but all edges will be
shaded in May. not much difference. It seems like one is better off
orienting the house so as to have the broad side against the
prevailing winds. So I will orient it NE-SW...
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