T5 switching to 400 hps flower

First off my grow space is 5ftW x 2ftD x 8ftH. The light being use now is a sunblaze T5-44 4 bulbs 20,000 lum. As for ventilation a 4" valueline fan and phat carbon filter attach. Day temps 75 and nights around 70. Out side of grow closet is 70 degrees. 40 % humidity. I will be flowering soon and I would like to switch to a 400 watt hps cool tube but I'm not shore how much more heat it will produce.

I go from T-5 for veg to 400w for flower. I have it air cooled and find I can keep it about 8 inches from canopy. It's the light intensity that is much greater than T-5 imo. I start them out at the edge of the light and move them toward the middle as they acclimate. I recently put 4 into flower using this technique. Big Bud, White Rhino, OG Kush, and Afgooey...the white rhino was a little touchy about the move but other than that things are good.

Sweet. I have two blue venum going. Their doing really well. But I know when it's time to switch 12/12 I will need more light and with prices not much def from running two t5-44 = 430 watts with 40,000 lum vs one 400watt hps 50,000 lum. So I'm really leaning towards hps.like you mention more intensity Defently. Just worried about if my valueline 4 in fan will Handel the heat coming from a 6" cool tube with a carbon filter connected to one end and then running out of a 18 ft duct outside. ( filter- light- 4" fan-14ft out side).

to be honest with a space like thats, 2 400s would be perfect, 1 400 will be alright but 2 would be where you want to go or the 400 and the t5(if you dont need it for another area)

I'll problly do one 400 watt hps and add the t5 as side light. I Ben looking into digital ballast Lumatek , phantum.What brands would y'all recommend useing?

1 600 wud be sweet..i think for a 5ft wide area u wud want atleast a 600 unless u dont plan on filling the whole area 400 is best using a 3x3 area but it can still work in tht area. def use some supplemental lighting to get those dark corners a few CFLs shud be fine. good luck