i like the trash bag idea i just thought of something to when you suggested that. the big home depot contractor bags dont let any light through you could put the lights a few feet off the ground in the same room as the plants with a trash bag over it but not tight at the bottom. the trash bag will keep the light out and the lights facing up will further keep the light away from your plants but still let the heat fill the area and the bottom of the trash bags will still let air exhchange enough to get u through the night, even though in the dark cycle plants do not need any co2 as they are not photosynthesizing but the root still need oxygen.

-secret