Growing canopy inside my garage, have some questions.
I'm building a 6' x 6' x 8' frame to house several plumerias (among other plants) to thrive during the cold months. I'm looking for a 1000-watt metal halide to provide lighting and heat, probably 12 hours/day. I'd appreciate any advice to the following questions:
 What to use for coverage? I've narrowed it down to either mylar or the reflective insulation sheeting at Home Depot. I'm thinking that the insulation material is better, since it keeps in the heat as well as reflecting the light, whereas the mylar is mainly to reflect light. Am I right?
 Is it a good idea to leave the top (where the lights will be hung) uncovered, for ventilation, or will that be wasting my heat?
 Should the plumerias be on the concrete floor, or on a table?
 A fan will also be used to provide air circulation, I'm not sure how many hours to have it on, or if it should be on at the same time as the light.
 Where do you guys get your lights? The cheapest 1000W MH I found is about $270 at hydrowarehouse, but shipping is at least $90, so I'm looking for some alternatives.