Re: the deep freeze

At 11:08 AM 12/19/1998 -0800, you wrote:
>Gary wrote:
>
>>In case you have not listened to the Weather Service
>recently, we are
>>supposed to have a near repeat of the 1990 Christmas deep
>freeze
>>beginning on Sunday night. 
>
>Yikes.  People living in truly cold climates will probably
>laugh, but that freeze was pretty traumatic for those of us
>who don't normally get freezing weather.
>
>Maybe some of our members who live in true winters can give
>more advice...
>
>Mike
>San Jose, CA (zone 9, min temp 20F -- we'll see)

Mike:

You will need to protect your outdoor water taps.  This can be done by
setting the tap to drip slowly.  I do this when my overnight temperatures
get below 10 degrees, and there is no adequate thawing in the morning.
There are different building codes in your part of the country that may not
specify the use of a tap with a valve as deeply set into the wall as we do here.

Freezing takes place for two reasons: loss of heat by conduction from air or
water flow, and radiational cooling.  A sheet of solid black plastic will go
a long way, especially if there are no air leaks, and the plastic is not
resting on the plants.

I have two cold frames (16 x 8, rising from 2 to 3 feet, and 20 x 8, rising
from 1 1/2 to 2 1/2 feet).  During a March hard freeze 5 years ago, I lost
power for the three days of the freeze.  I kept out freezing for these days
in a single poly 17 x 38 foot greenhouse by covering with black plastic, and
using one single-head Mr. Propane heater.  The cold frames had the
transparent areas  (sash and front wall, glazed with 1/4 plexiglass) covered
with panels of 1 inch blue wall foam, using a fastened tarp to hold in air
and heat and the panels on.

The first night after the precipitation, there was a 35 mph wind and a low
of 18 degrees.  The second night, no wind, and a low of 8 degrees.
Inspection the next day showed no evidence of freezing in any of these
structures.

By itself, the propane heater without the black plastic provided a 4 degree
temperature improvement.  With the black plastic on, I got a 16 degree
improvement.  A word on safety:  I had a carbon monoxide monitor on a post
near the burner - it never developed a danger color change over the whole
winter's use.  I also vented out the greenhouse before entering to turn off
the gas.  Evidently, the house was loosely sealed enough to allow enough
oxygen into the greenhouse.  I never noticed a sour odor when entering, and
the heightened water and carbon dioxide seems to have helped the plants.

Richard F. Dufresne
313 Spur Road
Greensboro, NC  27406
336-674-3105
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