After lots of reading I fould a formula for heat transfer that I think will be helpful for alot of closet/stealth growers

The formula is:

Q = V x P x C x dT

where:
Q = Amount of lighting (kW)
V = Volume of air being ventilated (m3/s)
P = Density of air (assume 1.2 kg/m3)
C = Specific heat capacity of air (assume 1.02 kJ/kgK)
dT = Temperature difference between ambient and growspace air in degC

***To get from CFM to m3/s divide the CFM by 2119.

You can solve the equation for different things based on what your need...

to find the temp change from outside the cabinet to inside

dT=Q/(V x P x C)

For my next grow room with a 400w light and 200cfm fan

dT=.4/(.94x1.2x1.02)
=.4/.257
=3.47+21c=24.47c or 76f

to find approx the amount of vent you will need

V = Q / (P x C x dT)

to find the most lighting you can have

Q = V x P x C x dT


kinda cool...don't know how accurate it is real world tho

try it with your own stats and see how close it comes