I just finished building this DIY evaporative cooler more commonly called a swamp cooler to keep my ladies nice and cool this summer. It is easy to build and works great. I have a 3 x 6 under 1200 watts and I am getting 10 degrees of cooling with only a 100 cfm fan.
DIY Evaporative Cooler Build Details
You can get full build details over at: http://420dotcom.com/build-a-homemade-swamp-cooler-for-your-grow-room.html
You also get some added humidity with a swamp cooler which is good for most growers because hot lights can make things really much too dry for your plants to breathe properly.
Low humidity and high temps reduce yield and make for looser buds. So give this a try and your plants will thank you.