Like the majority of Japanese houses, we only heat our dining/living room area. It means that when you need to go to the toilet in winter you hold on as long as you can and then make a dash for it to the little room and feel very grateful that the toilet seat is heated! It also means that the bedrooms are very cold so you learn to love the fluffy Japanese blankets.
I personally don't mind having a cold bedroom, but I do like to have warm feet so I always take a hot water bottle with me to bed to take the chill off. Last night I went to fill up my hot water bottle, that is usually waiting for me in the bathroom, when I couldn't find it. I was about to accuse one of the kids of stealing it when I thought I'd check in my bed first.... oops... not only was there one hot water bottle, but there were actually four of them hiding under the blankets! I felt slightly relieved that I didn't go storming up to the kids rooms before checking..... I guess I am the only one actually using them in this season!