Medieval people thought, as we do today, that they lived in modern times. They had no sense of the middle ages or the word medieval. In the twelfth-century, fireplaces were just becoming common, and they were considered a great innovation. Imagine getting rid of the smoky fire in the middle of the great hall and boasting about having fireplaces.
I have little doubt the heroine of my trilogy, Viscountess Ermengarde, put in fireplaces when she refurbished her palace in Narbonne. To read more about her and the medieval world, please consider nominating my novel on Kindle Scout.