Four-season locales face a dilemma once winter sets in. How to extend the life of your garden (and keep alive those plants that are still producing in fall)? The answer is easy: build a cold frame.Cold frames serve as mini greenhouses.
Use rigid foam insulation, which will provide a thermal break and not trap any moisture. Make sure you Tuck Tape every seam, and spray-foam all corners and joints to create a seal and a perfect thermal break.