The most costly option to the environment costing nearly 10x the amount of CO2 vs refurbishing an old house.
The house is already here, just may need a little work. Normally not as efficient as newer homes, yet some nice old homes were built with double walls providing better insulation than fiberglass.
These tend to be much more sustainable than traditional homes yet tend to be made of old tires and stuff from landfills.
Just sand, clay, and straw (or some other 'rebar'), cob is a very natural and cheap way to build although labor intensive. Very sustainable when combined with ideas from earthships (minus the trash). Requires very thick walls to maintain stable temperatures inside.
The best of cob tucked inside a hill side greatly reducing the amount of work required for walls while providing much more stable inside temperatures. Less light than the other options although sky lights can be added.