ANSI/ASHRAE Standard 160-2009, Criteria for Moisture-Control Design Analysis in Buildings, was published in May 2009. This engineering standard was developed over the past 13 years by an international committee chaired by an FPL scientist. The standard embodies a quantitative, performance-based approach to moisture analysis for evaluating building designs. Questions about design features such as the need, type, and placement of vapor barriers cannot be answered objectively or consistently without specifying the interior and exterior conditions that the building is expected to sustain without negative consequences to itself or its occupants. The standard provides criteria for selecting design parameters such as initial moisture levels in building materials, interior temperature and humidity, air pressure differences, and exterior weather loads such as wind-driven rain that affect the building envelope. The standard also gives criteria for selecting analytical procedures and for evaluating moisture performance.