It is the same with me. Below 10 or 12C is just too cold, but anything above that feels fine, as long as I can keep my toes and fingers warm. So I will often sit in my cold house wearing pac boots and gloves with the finger tips cut off, so that I can still type. :P

Although when it starts getting below freezing fairly often, I have to keep it set a little warmer or the pipes under the house will freeze.

I think maybe it is all about what one is used to.... I have met people from warmer climes who feel like 18C is so very cold, and who will shiver and wear a sweater in that sort of weather. Hehe.