protected cold frames
Kathleen Sayce (Tue, 20 Jan 2009 18:13:14 PST)

Jim,
Thanks for those details. Let me tell you a bit more about the
conditions we see here in winter.

I garden in USDA zone 8, sometimes zone 9, depending on the strength
of El Nino-Southern Oscillations and where the Pacific Decadal
Oscillation is its cycle, which now definitely is in the cooler
wetter part of its cycle. During warm dry cycles & ENSOs, frost free
winters are common. During cold wet, the present winter is typical,
solid zone 8 to upper zone 7 weather. 85-100 inches of rain is
typical, most of it falling in fall-spring, with cool dry summers.
This is just above the Columbia River on the coast, in the Pacific
Northwest. In the recent cold spell this winter & late fall, we saw
temps to 18F here (actually 22 at my place, but I'm in a warmer spot
than the official weather recording station), and our winds are
routinely above 80 for several storms each winter. Last winter we had
3 storms in 3 days, with winds during the last two 120 mph plus. The
anemometers all died in this area, so we don't know what the max
winds were––the devices reached around 127 mph and blew away.

My problem, or should I say dither factors, in deciding what to
build, have more to do with excessive wet and very strong winds than
with winter cold. So I envision my proposed cold frame primarily as a
rain shelter, but one that needs sturdy construction so the glazing
can be tied down/anchored/bolted in place in strong winds. I saved
some polycarbonate twinwall glazing from a recent sunroom rebuild
(not mine, unfortunately, but our rental place), so plan to use this,
as it can take direct strikes from wind-blown branches and clams
dropped by crows (did I mention the tidelands a few feet away?),
which all hard surfaces, including cars, roofs, decks and roads, are
subject to. I also know I'll be trying copper strips for slug and
snail resistance.

The dither factors that remain include: inside height when closed.
Anchoring the panels, when open or closed, in the wind. How deep to
set the gravel base for good drainage.

So, your information helps me, though as you can see, I am still
pondering, and would love to hear from others about their systems.
I expect an alpine greenhouse is in my future, to deal with the above
issues, glazed with something very sturdy.
Thanks,
Kathleen
Near the mouth of the Columbia River on the Pacific Ocean, where
today it was clear, sunny, and above 60F. Snowdrops and crocus are
flowering in my garden.