Why wearing black three days in a row doesn't matter...

I have just remembered why it doesn't matter if I wear different black shirts every day of the week at work. I work in the basement of a library where I consistently start to freeze for the entire day only an hour after arriving. I combat the frigid temps in the recesses of my dungeon by wearing the same black zip up sweatshirt everyday (sometimes I also wear a second pull over), and no one gets to see my endless supply of black shirts.