Washington's home was not looted and pillaged by Union troops like so many other Southern civilian properties because,

1. Washington was dead so they couldn't spite him like they did Lee.

2. The house was empty nothing to steal.

3. They left Sarah Tracy at the house believing that the presence of a lady would protect the house from unruly soldiers (sure didnt work at Roswell Georgia).

4. They had a written order from General Winfield Scott for soldiers to lay down their guns when they entered the grounds.