equipment in wall cabinet - how much ventilation?

[basementjack]

I just built an in wall cabinet for my components.

I'm concerned about ventilation - I don't want to bake my components!

It is a simple cabinet with room for 4 components (3 shelves, plus the bottom)
The front is open, the back is currently covered by black fabric.

I'm going to install a 120mm fan in the top of it, to pull air from the top of the cabinet out.

However, I'm concerned about the components on the lower shelves.

Is it worth doing something elaborate?

One thought is that If I replaced the fabric with a door of some sort, I could install additional fans on the door - to vent straight out the back.

Any thoughts would be appreciated!

Lastly, I was going to rig something up with a relay so that my 12v trigger would pull the relay, which would in turn, provide 120v to the fan(s) - Is anything like this already made or is this going to be a project no matter what?

[Paul H]

If you're going to install a fan at the top which exhausts somewhere outside the cabinet, air is going to also be pulled into the cabinet through/around the door.

Just make sure there's some space underneath the door and that air will come in at the bottom of the cabinet.