Oh, I forgot about that stuff. It was that fiberglass material that you roll between the 2x4's. We had the attic blown.
Well you certainly built a tight home, LOL! Enough material can attenuate a cell signal, and you likely live in a "dead" zone, these are areas that, because of geography or distance, receive a weaker signal than normal (my brother lives in one such zone, in a city, you have to step outside to get enough signal to make a call).