try using aircooled hoods on your lights and connecting it to a squirrel cage exhause fan

orchidgiant, I'm having trouble understanding your setup. How is your room vented to the outside? Does it have any windows? Where is the fan that pulls air through the room? Where does the door to the basement lead to? Are there other rooms in the basement, and do they get cool enough at night? What are nighttime temperatures outdoors? Are you trying to lower the temperature during the day, or just at night?

I generally use a window fan to cool my small grow room. (All my plants are now outdoors for the summer.) At night, when the light's off, it's still a little warmer indoors than out, because the building retains heat.

The exhaust van is located in the back of the room, along the ceiling. Air is moved out of the room, through a duct to the outside. (I put a hole in side of the house for the vent, and my loving wife says no more holes, or i would just put a vent to allow cooler outside air back into the room)

The room is freestanding, covered with plastic. There are no other rooms in basement. The basement does get cool, about 65, at night, but my grow room does not get that cool. I am trying to find a way to make it cooler.

Thanks for the help, i will look into the aircooled hoods.

also try a window ac unit. just make an enclosure for it and hook up an exhaust fan to the enclosure. make sure your enclosure has a carb on it so air can be pulled from it

Have you tried reversing the direction of the air flow? Pull cool air from outside and push it into the basement.

Another simple trick is to place a hassock fan on the floor of the grow room, to move cool air from near the floor and circulate it upwards 360°. Combined with a few small vents in your plastic, this might help move cool air in and push warm air out.

I'm also growing orchs, but in quite an enclosed place ('Indoor Greenhouse'). I installed a little fan inside which I just turn on for a short time when it seems to need it, but it never gets a lot cooler in there (~5 F.) o-night (no fan on) and the plants seem to be fine. I worried at first about it, but I think they've adapted pretty well... I have Dens. and Phals. and Vanda and Miltoniopsis and BLC's and Tillandsias, Broms, kumquats, a banana, etc. The lighting is a specialized kind that came with the g-house, but doesn't put out a lot of its own heat. I can't let it go very cool (below about 68-70) because I also have a betta fish in a 10 gal. tank in there with the roots of a drac. ("Lucky bamboo:) and piece of a peace lily in the water... and the fish needs to be kept warm.