if u use foil thats on someone else to explain but the card board is easy
take a box n cut just big enough for the light/lights to fit in then leave about an inch in the middle for air flow this will lock heat and humidity it
also i use sphagnum moss in a plastic bowl under my snakes light to make it humid
if u dont have this then im sure wet paper towel would work <?
I would think that cardboard would be a bad idea, because it would suck in moisture and possibly mold if there was not enough air circulation. Sphagnum moss is great though.