Seriously mate, your use of Stefan Boltzmann Law and IGL.... You are at the first peak Using the SB Law with a temperature of 16 degrees Celsius gives a calculation of 288K - You must agree with this as it's all about the MATH!!! But using SB Law in it's true representation (of a closed system) gives a calculation of 255K
Give it time and you'll be on the Slop of Enlightenment but for now enjoy the Valley of Despair