Cardboard box

At least invest in a rubbermaid box. Cardboard is a diaster waiting to happen.

 

Yeah dude, using cardboard is asking for a fire, atleast grab a rubbermaid or a couple small sheets of plywood or hardyplank(fireproof) that you can apply some mylar to and use as reflection.

 

rofl!!! u won't set cardboard on fire with a cfl!!!
line it with mylar if u can.
mylar is flame retardant btw

 

Still in my opinion it sounds like a bad idea.

 

i'd imagine your worst problem will be moisture. it'd probably end up going soggy and falling apart.

 

its not just heat thats a risk wot about elec faults, just stay away from cardboard, get a cupboard if u cant build a box in a room corner using ext grade ply only, and line with mylar or paint matt white, if u opt for painting (most cost effective) you will need a few coats of paint.