Yeah mines vertical. Just saying tho, Bignugz420 is worried about heat. If he is fine using a 315 then heat may not be an issue. I don't know what the benefits or cons are between having the bulb vertical or horizontal. I have my tent in a basement closed room. Its been in the 20s to almost 60s past few weeks. Duct work closed off as I was hitting 85 at the highest. I also have a heater in there to keep it from going under 65 degrees during lights off. I think the tent was sucking in the hot air and that's why it got to 85 degrees. Relocated the heater so it isn't pointing right at an intake but left the duct work closed also. Now I'm around 78 degrees to maybe 80 and still only bottom out at 65.
Summertime I couldn't say. Again tho, my tent is in a naturally cool room. Oh. I'm only running 4 inch fan too that at its best is prolly only minimum recommended