I would like to encourage anyone thinking of building cold frames to do so.
Several years ago we built them along the east side of a building. They run about 16' or so, have tops made of double polycarb set in cedar frames which slide open and close. It is divided into 4 "bays", so there are 4 tops.
It's a great place to transfer perennials early in the growing season, tp protect plants from inclement weather be it cold (like last nite's freeze) or too much rain, help plants adjust to the outdoors, etc. It's amazing how warm it is inside of these when its' chilly outside.
I'm fortunate to have a greenhouse, but if I was starting plants just for me, these would be all I needed.