Need help cooling my air

Okay so, for my first grow i built a grow closet, in a garage....it gets around 81 degrees inside the of the garage. The closet itself is around 82 degrees, (it varies at different times in the day, depending on how warm the weather is) At night, the temperature in the box drops down to 76 degrees (which is bascially what im aiming for). inside of the box there is 1 400w mh bulb with an exhaust attached running outside of the garage. The humidity in the box stays around 50% most of the time.

I was wondering if there was a way to cool the air without running another duct out of the box, without drastically lowering my humidity? (which is already pretty low)
Thanks for the help you guys

what size fan is hooked to your exhaust? Is the ducting insulated? what size is your room?

I'm not sure what size the fan is, it was was one made especially for this light though so it can't very powerful. The closet itself is 8.5x4x7. and the ducting is not insulated.

I think you want to make sure you always have more air leaving the room than coming in. Negative pressure is what you are shooting for. I think adding a six inch inline fan to take air out would be good for your space, especially if it is pulling through the light.

If possible you want the fan to pull the air, not push it.

I'd set it up like this: either an open end or sufficiently sized cfm can filter on the air intake side of the hood, inside the room

ducting leaving the other side of the hood - going to the 6 in. inline fan and exiting to the attic.

run this fan 24/7

there should be enough passive air being pulled in through cracks to re-supply the rooms air.

adding insulated ducting will reduce heat and fan noise, and eliminating as many bends in the ducting is important too. each 90 degree bend in your ducting will reduce your inline fan's cfm's by 50%.