Actually, all you have to do is line the inside edges of the box with reflective insulation. It would heat up the box from the sunlight enough for the plant to thrive. You just have to make for sure that the cover (you can make it using plexiglass) does not get blocked by snow or dirt. I've seen another video where the person did that. The box was covered in snow when they went to check it. When they opened the box, the ground was moist and the plant was healthily growing inside. It gets below freezing here and I fully intend on doing that.