How to best light 4'x3'

I am a former outdoor grower recently moved to indoor. I started out using fluorescents and am now wanting to try using HID lights.

The space I would like to do this in is a closet, 5’x3’. The ceiling is angled and at its highest point is approximately 6’, but the light will be hung from 5’. I won’t be using an exhaust system; just a large room fan that oscilates.

I won’t need to light the whole room because I want to section off a 4x3 area for the plants and set up a SCROG. I would like to put 5 plants in that space, so I would use 4 gallon soft pots. That means that light has to cover a 4’x3’ space, or 12 sq. ft. I would like a minimum of 50w per sq. ft., so that is 600w. Each plant will have 2.5 sq. ft. of growing space and I am expecting atleast 2 lbs.

So, my question is how do I light this space with HID lights. I figure that the 600w lamps would be perfect for coverage, but that the heat could get out of control with such low ceilings and no exhaust. Although the fan I would use is much larger than I would normally need in that space. I worry that two 400w lamps wouldnt adequately cover that space since, as far as I know, they cover 3.5’x3.5’ effictiently and my space is 4x3. Meaning they would overlap in length and fall 6 inches shy in width. I feel like 250w just wont work so now I am looking to get some advice. Any and all will be appreciated.

Also, what sort of temperature difference is there in using two 400w versus one 600w? Or even the difference in two 250w versus one 400w?

“I won’t be using an exhaust system;”

No vent/fan on the light?
No fan sucking air out of the closet?
No carbon filter?

Will the door be shut all day? How warm will the room the closet is in be? Will you air condition it?

1 Like

I don’t have a ballast yet, but was thinking of one that just has a hood, no fan. No airflow into or out of closet, no AC. The room on its own will be about 70 F. Door closed. I’m thinking of having a second fan with carbon filter freestanding in room.

You may need to rethink your parameters…
The plants need fresh air flow.
The hid light/lights are hot and will warm the air, more so with no fresh air, no air conditioner, no venting.
You may have temperature problems starting out at 70 F. If you did, how would you fix them?

Dim the ballast and compensate with fluorescents.

Given your parameters I would recommend you consider LEDs. I’ve never used them, but I have used HIDs in areas that size and you’re going to have heat issues with any hid much above 250w, particularly in the summer