So in the end cypress was specified for the shingles.  Cypress, which is also a very rot reistant wood, was specifically selected because it was commonly used for shingles throughout the 18th and 19th centuries.  Other historic homes in Virginia that used cypress shingles include George Washington’s Mount Vernon and Salubria.  As a result, the roof of Montpelier has been restored with materials Madison would have been familiar with but which will also protect the irreplacable 18th century roof framing for many decades.