A measure of the loss of use of property that has not been physically injured but that is less marketable because of the presence in it of a known defect. For example, a building constructed with substandard materials that have not yet shown any physical damage but are certain to do so over time sustains a diminution in value. One purpose of the commercial general liability (CGL) "impaired property" exclusion is to eliminate coverage of diminution-in-value claims.