Best Way to Vent Heat to Keep Temps Low?

Apologies for the awkwardly worded title, and, the search results I found weren't any help...so...


Here's the set up:
3ft x 4 ft grow space with a 3X3 flood table. The space is approx4 ft high.



400W HPS worth dimmable ballast


Dayton exhaust fan. 120ish CFM running constantly.



The ambient temp inside the space is 80-85 with the light on.


Up in the canopy, the temp is in the high 90's.


The reflector is a "W" shape with a sheet of tempered glass in place.



There is a 1 inch gap between the glass and the reflector on the sides, and a 4 inch hole in the rear of the reflector.



The fan is in the space and sucking ambient air from near the reflector's 4inch 'exit' hole, and then blowing out a 4 inch duct to the attic.


What options would be the most effective for helping to lower the heat:
1) Connecting the fan intake directly to the hood.


2) Putting fan in the attic and running inlet hose down to reflector.


3) Turning the 400W down to 75% and running at 300W. ( I like the light close to the plant due to an unreasonable fear of losing a couple lumens cuz inverse law thingee.)


I'm trying to tweak and optimize my set up and the heat has always been an issue in this spot. And I'm sucking up a lot of my expensive AC'ed air and blowing it into the attic. Is there a reasonable thermostat I could use for the fan?

Well dropping to 300 has obvious repercussions, and extracting through the shade with a little more certainty to. You could also insulate the top of the shade with rockwool? to stop heat escaping that way.

You know you need a $150 240w QB though.


Edit: It's possible that extracting right off the roof could help. Hot air rises. So ducting positioned to just 'shlurp at the coffee' can be a lot better than 6" lower.
Water cooled lol

you need quatum Boards Led

f-e said:

Well dropping to 300 has obvious repercussions, and extracting through the shade with a little more certainty to. You could also insulate the top of the shade with rockwool? to stop heat escaping that way.

You know you need a $150 240w QB though.


Edit: It's possible that extracting right off the roof could help. Hot air rises. So ducting positioned to just 'shlurp at the coffee' can be a lot better than 6" lower.
Water cooled lol

Click to expand...

Yep, I'm afraid that the yield would take a hit with the lower light power, but I wonder if moving the light far enough away to keep the temps OK would be sufficient with casing as much of a yield decrease.


You sort of summed up what I was asking- it it better to vent the heat at the top of the room ( my thermometer showed the ceiling area above the light to be just slight over the ambient temps. I was actually surprised by that.), or is it better to connect to the hood and vent it...


I also wonder which reflector would give the best compromise between coverage and being easy to vent.
Do the cool kids still use the cool tube designs?