Need Help with Grow Room (Heat)

I have a 4'x5'x6' box i built in my backyard out of osb and pine 2x4's and during the day inside it is getting as hot at 100 degrees with 1 400w hps light. i have a cooling fan attached to the light hood. I can invest in a portable ac unit but am wondering if that is the best fix for my problem. the grow box is in direct sunlight atleast 8 hours a day. I will try to get pictures by tomorrow

Any chance you can move the box into a shady area?

That is a problem. You cant cool it with blower/exhaust as the air outside is just as hot, also a cooltube is useless and so is the cooling fan you have in there, its just blowing hot air around. The a/c and shade canopy is the only option i can think of.

Yeaman, add an a/c to that bitch. I'm using a plywood box with a 400w too, lol. 5000 btu drops my temps by 20 degrees F, you might need a 6500 btu because your box is 30 cubic ft bigger than mine and you need a temp drop of more than 20f.

Problem with a/c is co2 depletion, so I set my vent fan on a timer, on for 5 min every 1½ hrs to refresh the air in my cab. (my timer has 8 on/off settings and flower is 12/12)

edit: lol@ growing outdoors in a box