"chaz" wrote in message ink.net...

Rick,
How do you handle heating, ventilation, etc? Where can I buy plastic for
this project?

I am not rick, but here is what I have to say:

1) I buy the clear plastic at the store. Yes, it is not UV resistant.
You will have no UV damage until late in the season. I usually uncover
my beds on April 1 and store the plastics in the dark. Plastic lasts
two years at least and is usually done in by pulling it while it is
covered with ice (it breaks). One roll of 4mil clear poly, from the
Home Depot paint Dept, is some $25. Plastics never broke under heavy
snow, though it did form puddles. Also the PVC hoops are quite flimsy.
I bought clamps for plastic at Territorial Seeds.

2) don't ignore irrigation. my tunnels are over a depression in my
yard, where runoff water collects, and so even though I don't water in
the winter, they get plenty moisture a few inches below the surface.
But the first few inches of bed soil are Sahara dry by January.

3) the soil provides enough heating and cooling, at least for low
plants like salad greens, as long as mulch is removed so that there is
good thermal contact. I never had a problem with kale or collard
either. Otherwise, the standard way to cool/heat a greenhouse is to
cover the North wall with 55 gallon drums filled with water. Each has
a thermal capacity of 40 MegaJoules, which sounds like a lot but it is
not. This is a little project in itself, as you probably have to stack
them two high and secure them with chains to sturdy posts to avoid
them falling and killing people.

4) ventilation for cooling is needed only in some cases (not for my
tunnels, though it will be needed for my greenhouse). The standard way
is to have two temperature operated louvres, one at the door, one
opposite. They open ad create a draft when the temp exceeds 85F. They
are thermal powered. I bought mine at Territorial, but I have not
installed them yet. ventilation is also needed for CO2. My soil has
enough organic material that CO2 is not a problem. If in doubt, a pile
of manure in a corner will provide enough.