OK, there are many places where extra clothing isn't enough, but I think most people are accustomed to an indoor temperature far higher than is necessary or healthy. It feels comfortable, but then so does morphine. Whether it's -40 or +5 degrees centrigrade outside if the temperature inside is kept at 21, reducing it to 10 will have the same effect on the people (and water pipes) living inside. Elderly & ill people need higher temperatures than the rest of us though.