Options:

• Wood
  • + Lightweight, insect resistant
  • + Environmentally friendly
  • + Looks the best
  • Look for FSC or SFI certification
  • Can look into bark, burnt wood, reclaimed barn siding
• Steel
  • + Recycled
  • - Labor intensive

Conclusion: Go with wood, base type on what's available locally and aesthetics.

Cost: $17,280 = $8 / sqft of wall space * 2160sqft. Wall space = 900sqft of floor space = 30ft * 4 perimeter * 9ft wall height * 2 floors = 270 sqft * 8 = 2160sqft.

References:

• Eco friendly siding
• Reclaimed bark siding
• Green siding options
• Ecohome exterior cladding
• Shou sugi ban wood siding