Hot box need to be make in respect of rules of art. Not a quick cheap built. Use ventilate heater with thermo regulater and security. Those one for bathroom works good up to 45 degree C.
I only wish me house was worth 500,000! Yeah, its only been used once under close scrutiny and is hopefully now obsolete as I’m curing my skins pre-build with a pensioner’s electric blanket (hope its not a harsh winter). Its an experiment at mo that may fail hainously, but maybe, just maybe???..