That is an interesting observation regarding marginal utility.

In your example, it looks like people have the option to not enter the office and therefore avoid the cold. What if the cold temperature cannot be avoided? It is -20C inside and outside the office. Therefore, -10C would have to be an improvement over -20C. At -10C, you could wear a nice warm coat, a scarf, and maybe some mittens. At -20C, you will probably need some special gear to stay warm and survive.