Mmmm, couldn't say for sure. My GH is a not-very-well-insulated wood frame structure that at it's best will only add about 10 deg to outdoor temps without adding heat. I guess a lot depends on how large and how well insulated yours is. I've been tinkering with adding insulation to mine for several years now, so it retains heat quite a bit better than it used to. A lot of people recommend putting jugs of water in the GH to soak up heat during the day to help keep things warmer at night. However, when I've tried leaving jugs of water in MY GH, I end up with frozen blocks of ice!
