right environment under glass

Hi, I am building 5 raised vegetable beds all exactly the same size and intend building a polycarbonate frame about 600mm high to place over at least 1 bed but with the ability to move it to another when I wish.
Question is should it be air tight or how much air should pass through it to avoid the wrong conditions. I will not be using it as a hot house but to force early vegetables from February. We live in an area prone to late frosts up to June (even though I live in sunny Suffolk).
Any help will be appreciated.
Regards.

 

Bearing in mind I don't pretend to be any sort of expert - but I'm thinking that if you're making a 'lid' to go over one or more of the beds merely to protect from frost, then that lid in itself, should be sufficient. If you want to force vegetables, then I think you'd need to think about making a 'hot bed' - for which you're going to need a lot of horse manure.

 

I agree with Shiney. What you are making is a great big propagator - which is an excellent idea. Most of the time you will want it fully shut. But you will need some facility for ventilation for those odd occasions that Shiney mentioned.

My inclination would be to have some sort of hole in the top, which could be closed. This to let the air out (hot air rises), and you could let the air in at the bottom just by lifting one side up with a brick. I would also want to put a thermometer inside - just to get a feel of what is going on.

 

Hi Peter, yes you are right about what I am trying to achieve

Great idea about the thermometer.

I have never used glass in the garden before so need all ther help I can get.

 

Thanks for the help guys