To answer the question the Restoration Team analyzed the dates of the architectural finishes found in the Mansion’s other rooms.  After the analysis was completed, it was discovered that all of the mantels in the ca. 1797 section of the house dated to ca. 1812.  The dates were based on nail evidence as well as the fact that the carpentry bill for the ca. 1812 renovations includes references to the mantels.  One theory that would explain the ca. 1812 mantels in the ca. 1797 section of Montpelier was that President Madison simply replaced the mantels in 1812 with more fashionable examples, similar to how he treated the windows.  However, the Restoration Team also found that the mantels in the ca. 1764 section of the house were not replaced during the ca. 1812 renovations.  Why would Madison have replaced all of the mantels in the ca. 1797 portion of the house, which would have been much more fashionable than the ca. 1764 chimneypieces, and yet leave the ca. 1764 mantels in place?