The true event that the movie is based on happened in Georgia, where this film is made and filmmakers are from. 4 friends were in the sauna, one left for the toilet, locking his friends in - exactly as it is shown in the movie. He never came back, and when he woke up he didn't remember that he left them in the sauna, and started to search for them elsewhere. Fortunately no one died since they managed to turn the heater off, but they had to spend over 10 hours in the decreasing heat, until they were found.
Travis Van Winkle was in the remake of Friday The 13th (2009) which Scout Taylor Compton auditioned for the role of Travis' girlfriend Jenna that went to Danielle Panabaker instead. Scout had just portrayed the Jamie Lee Curtis role in Rob Zombie's remake of Halloween and its' sequel Halloween 2 with another famous Danielle (Harris) and Tyler Mane as killer Michael Myers.
Scout Taylor-Compton and Tyler Mane also co-starred Halloween (2007) and Halloween II (2009).
When Ian got shocked, that couldn't have happened. Thermostats are connected to 6-30 volts AC current. It could give a sharp bite if shorted to a human body, but wouldn't spark and electrocute him like that.