Appraisers use several factors when estimating a home's value, including the home's size and square footage, the condition of the home and neighborhood, comparable local sales, any pertinent historical information, sales performance and indices that forecast future value. For detailed information on appraisal standards, contact the Appraisal Institute at 200 W. Madison, Suite 1500, Chicago, IL 60606, 7 a.m. - 5 p.m. CT; 888-7JOINAI (754-4624).