I think you understand the issues with the attic installation. The foil is a 100% barrier to TV signals, and the roof edges may diffract the incoming signal, generating local nulls. And wood/vinyl is not radio transparent.
If you mount outside, the antenna needs to be grounded properly to protect you and your family. This is a good thread about grounding -
http://forum.tvfool.com/showthread.php?t=901