Dear Jane,Dear Jim, Obviously I did not follow all the contributions so it is the first time I hear about your protected cold frame. It sounds most interesting and I have had the idea to build something like this for many years in my garden but have not yet done so. 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 close accordingly. Is much simpler and cheaper than motorized thermostat-controlled ventilation. YES, PLEASE re-publish the article on cold frames for us PBS-members! greetings from Germany, recovering from one of the coldest periods recorded...... Camellias and Trachycarpus alive (so far) Chamaerops (experimental planting) and Sabal probably dead. Uli