Well, I wasn't having much luck with my plants indoors in the garage. I was running an electric heater 24/7 in order to heat the garage, even after insulating the whole space. The max temperature was only reaching 65 degrees, and getting into the mid 50's at night. Lower leaves started shriveling up and dying, possibly mites, temperature, or lack of light (600 Watt HPS), and I saw no noticeable growth at all.
So I built this grow box! It is 4 ft wide, by 8 ft deep, 8 ft tall on edges coming to a peak at 10 in the middle. I have lined the whole interior in Mylar, though not as smooth as I would like. Overall, this is awesome though! I have already seen noticeable growth in 3 of my 4 plants, and can heat the room from 55 to 90 in less than 20 minutes!(Not that I am keeping it that warm) The only concern I have now is keeping the humidity up. I am using a Humidifier, and spraying the plants often, so hopefully they keep growing for me.