Trying to figure out the right temperature

As we are so lucky to live in a part of Iceland that has geothermal up-warming of our houses, we have (for the first time) floor heating in our home in Hrísey island. But as it has been very cold (minus 10-13 degrees) and very windy at the same time, it was also rather cold inside. We have not quite found out how everything works, but we phoned the plumber and he advised us to turn the heat way up. Which we did, but it took a day or so until it was comfortably warm in the living room. So warm in fact that when I woke up the next day it almost felt too hot ...