I am a bit confused regarding which rating system I should register a project into. The project is to build a new hotel right (about 50 keys) next to an existing structure (17th Century castle) that already works as a hotel (about 9 keys). The owner wants a LEED Silver certification (at least). The existing structure will be renovated and used as a lobby and entrance to the new construction. Both are part of the same project. What should be the appropriate rating system? 

Thank you very much for your advice