The Collaborative International Dictionary of English v.0.48:

Habitability \Hab`it*a*bil"i*ty\
   (h[a^]b`[i^]t*[.a]*b[i^]l"[i^]*t[y^]), n.
   Habitableness.
   [1913 Webster]

WordNet (r) 3.0 (2006):

habitability
    n 1: suitability for living in or on [syn: habitability,
         habitableness]