There is a twenty degree difference between outside and inside

Why are office buildings always so fricking cold? The place I sit in to do research (which is a computer lab, so we don't need to keep living things at a specific temperature or anything) is always around 60 to 65 degrees. Outside it's a gorgeous 75 degrees, going to get up to 80--however, on days I work I have to wear a sweater, and sometimes a jacket. Hmph, my summer clothes are all going to waste.