How poorly would an attic mounted antenna perform? Obviously worse than something outside, I’m guessing, but how much worse?
My office has one of those “side attics.” It has a half sized door. Mounting a long antenna in there is very tempting because of how much easier it would be than doing anything outside. It’s on the second floor as well.
Wood and shingles. Typical single family American home.
On HF it probably wouldn’t be too bad since the signals would generally just go straight through the surface. On VHF and above though it could be problematic.