The temperature and environmental conditions in our climate zone change with the seasons, and also each day, depending on whether the sun is shining or the phases of the moon. Our body cannot always adapt to those changes and needs the help of different systems to ensure our body temperature stays as constant as possible.
Fire is our main ally to overcome the cold. The hearth needs to be constantly stocked with wood to keep it alight during the long winter nights; something we cannot do while we are asleep. The kitchen (sukalde, fire zone) has always kept the areas near it warm; the problem is how to heat the rest of the house and the bedrooms can be very cold at night during the winter months.