We need to replace our roof and are considering a metal roof as an option. I have had several different options recommended. 1) Old shingles removed first, 2) Metal roof right over top of existing roof, 3) Metal roof attached to 2 by 4 frame placed over top of existing shingles. Whats the best way to proceed in a climate such as Canaan Valley, WV? Any other suggestions? Have you heard of solar shingles and would they be worth considering?