This guy made a very cheap 3d printer enclosure made from cardboard box :-) It probably works and can be used as improvised heat chamber but there could be a slight fire hazard. But if you don't have any money, you will take some risks. I know that for a fact. You could also try using some salvaged drywall or gypsum plates.
Stay safe kids! It's always a good idea to have a fire extinguisher in your house.
If you need a different low cost solution you could try this one with cheap plastic boxes: