protected cold frame

Adam Fikso
Tue, 20 Jan 2009 17:19:54 PST

Thanks Uli.  I encountered these tyemperature-controlled devices as a 
youngster about 70 years ago, but did not know that they were hydraulic. 
Are they still being made? Energy-saving, I'd think and need to be brought 
back or re-popularized for today's world .

----- Original Message ----- 
From: "Uli Urban" <>
To: "Pacifib Bulb Society messages" <>
Sent: Tuesday, January 20, 2009 5:38 PM
Subject: [pbs] protected cold frame

Dear Jane,Dear Jim,
It was most interesting to read about your cold frames and thank you for
the photos. I use a simpler  different version to cover two beds on the
base of my greenhouse wall: one for hardy cactus that need just
protection from winter rain and one for tender perennials and half-hardy
bulbs. It worked wonders last year but I do not yet know how the results
will be this very cold winter. Some of the foliage at least looks VERY
dead. I bought old commercial cold frame windows from a nursery,
replaced the glass with polycarbonate (Plexiglas) which allows
UV-spectrum rays through, is lightweight and will not break. These
windows are leaning at an angle of about 45° to the wall and allow the
wind to pass in order to avoid overheating on sunny days.

For opening mechanisms there are automatic vent controls that work
without electricity. I used several of them in my old greenhouse. Once
adjusted they work forever very reliably, many different models are on
the market, I think they were invented in England and use the
expansion/shrinking of hydraulic oil in changing temperatures which is
transmitted by cleverly designed levers to the windows that open and

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