Amusingly, it’s Nancy-sized.
When I was driving home from taking Em to school yesterday, it was cold enough that there was heavy front on the roofs of all the houses. It was also light enough for me to see it and I noticed that there were places on some roofs that had no frost. Some houses had frost only on porches and overhangs- others had more but had spots where it had melted. It occurs to me that if the frost doesn’t stay on your roof, you could use more insulation in your attic and that would tell you exactly where. I was very happy to see when I got home that our house had frost all over the roof with no hotspots.