There was really cold weather and snow forecast for our area in the mountains of western Virginia, and I realized they would push the limits of the groundcover cloth I had been using for frost protection. So I grabbed two of the storm window panes I had picked up from Craigslist, took measurements, and built a cold frame to fit the window dimensions.
But what about actual fresh vegetables in the winter? For that, we need to reference the amazing work The Winter Harvest Handbook by Eliot Coleman. Coleman lives in Maine. He uses unheated greenhouses. In the winter. Here is how his system works: A single coat of greenhouse plastic and the thinnest row covers.