While mylar is a great reflector, the white walls of your fridge should be sufficient in terms of space, you should get rid of the mylar, it will trap more heat in there. A computer power supply to run a 12v pc fan is overkill..
While you may burn your plants with too much bulb heat, you're not going to start any fires with the heat from CFL bulbs (electrical fires are another matter), the melting point of plastic at it's lowest is about 110[FONT=arial,helvetica,sans-serif]° ([/FONT][FONT=arial,helvetica,sans-serif]Celsius), it's ignition point is in the 300[/FONT][FONT=arial,helvetica,sans-serif]° to 450[/FONT][FONT=arial,helvetica,sans-serif]° C range. Paper ignites at 232[/FONT][FONT=arial,helvetica,sans-serif]° C for reference.
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