Axios Des Moines: Polk County home assessments will increase about 22% next year. Polk County assessor Randy Ripperger projected the hike during a meeting last week with the Taxpayers Association of Central Iowa. He estimates commercial properties will increase about 18%. It would mark the steepest hike in residential values in the county's history, Ripperger said. The median sale price of a single-family home in Polk County was around $286,000 in July, up more than 12% in the last year, according to a report by the Iowa Association of Realtors.