Besides adobe there is another alternative, thermal and environmentally conscious construction method:

Straw Bale Construction
Plastered straw bale construction has been used for many years to build everything from luxury mansions to low-income housing. It is a technology which has proven itself over the last century to be durable, highly fire resistant, non-toxic, and structurally superior to many other systems used today. Straw is an annually renewable resource that creates highly insulated buildings which are both warm in the winter and cool in the summer.

This beautiful school in Querétaro was built with straw bale construction. It provides a highly agreeable environment, not only lower in construction costs but also in maintenance. It also provides a beautiful working space for both children and teachers.