my portable cold frames (2 people can easily carry them around, and they are just heavy enough not to be blown by strong wind):
each frame is 4'x6' and 3 to 5' tall, which is the most 'economical' size, given the price of 2"x4" wood, but same idea can be used for 2'x6' or 2'x8'
Re plastic - buy the best available, otherwise you'll be replacing plastic every 2 years or so.
Good luck dcarch! And please share your pictures with us, during and after construction
