Soil Mixtures in Dresser Cab

What soil mixtures do you guys use for cab grows? The mixture I use now 1:1:1 potting soil, vermiculate, pearlite. It tends to get very dense and heavy after watering. I would imagine it will suffocate the roots.
I have 8 Cfls and 2 2' floro tubes in a 5'x1'x2' Converted Dresser with 2 120mm pc fans. Stays about 38% humidity at 84-90 degrees F (a little hot, suggestions for cooling it down?.) 4 plants in 3 gallon pots, 2 plants in small hydro set up. More pics will come later, i will have to splice back into the ac/dc camera charger used for the fans, oops.
What is optimum humidity for growing, by the way?
Thanks in advance for the ideas.

if you have a grow shop nearby get sunshine #4 it a soiless mix containing perlite,moss,etc and i also like to use earth juice products with some molassas 3 tblspoons per gallon last 4 weeks once a week.

Ditch the vermiculite, it's unnecessary. Perlite works better.
Cooling, you need exhaust. A 4" duct booster fan in the back of the cab is a good start.

I think you have too much perlite and vermiculite, and not enough soil ... the other stuff is too light to support your plant ... I use 3 parts Happy Frog potting soil, 1 part perlite, and a handful of dolomite lime per gallon of soil mix ... :smokin: