In article k.net,
Shannon Hughes wrote:
I am planning on building a cold frame that will be either 6 feet by 2 feet
or 4 feet by 2 feet. I would also like to install a solar activated vent
opener on the box. Most commercial units of this size seem to have 2 - 3
lids (vents). Is it possible to have only one vent in the middle that is
about 2 foot by 2 foot in size....is this enough ventilation. My main goal
is to get away with only buying one vent opener.

My 4x4 cold frame has a single vent opener, which raises the entire
lid. The key is the weight that the opener has to lift -- which should
be specified for the opener.

An amazingly high temperature can develop in a cold frame on a sunny day,
so I'd be wary of trying to use a small vent on a large cold frame. I
once baked (killed) some sweet peppers when a vent was improperly re-attached.

-frank
--