Fespo, I like your GH very much! I like the heater! Don't let your plants get too close to it or you'll be sad! Mine is a tiny 8x6 with 2 long tables set a different heights so I can place both tall and short plants inside. I also place a tiny upright radiant heater inside to keep the temperature above 32.
I was going to upgrade mine to a 10x22 but since I only keep trees in mine during winter, I didn't want that space unused in summer. Greenhouses heat up fast when direct sunlight hits them. Nice job!