How is Hogwarts, the temple of the Harry Potter universe, heated?

In the novels, the films, and even in Hogwarts Legacy, it is evident that all sorts of domestic chores in the wizarding world are dumped on house-elves. Hermione, with her ability to look at things from the outside as someone coming from the Muggle world, even wants to enlighten others about how this is "exploitation." In the wizarding world, this is so ingrained that it is not even considered to be the exploitation of house-elves.

In the novels and films, the impact of house-elves on daily life is not seen clearly enough. In the game, you constantly encounter house-elves dusting, working, and sweeping the floors while wandering aimlessly in the most remote corners of the Hogwarts building at odd hours. They continue to work every hour, even when no one is around, and they vanish with a pop when they see you so as not to be underfoot.

In other words, in the world of Hogwarts, house-elves are behind every labor that is invisible to you, and yes, Hogwarts is heated by fireplace fires. The fireplaces are lit and controlled by magic or house-elf labor, but most of it is house-elf work. Exceptionally, it may have been seen that some professors tend to their own fireplaces with their own wands. In general, it is the house-elves.