without ventilation the plant can't breath because it takes in co2 and expels oxygen that oxygen builds up and is toxic to the plant , water and nutrients are taken up by the roots and transported to the leaves where the nutes are turned into energy so if that water can't evaporate the plant can't grow that's why you need a good ventilation system. you can make an enclosure but it will still need to be vented and light tight, cfls put out heat so you need to be able to keep it cool.