This question came up while my brother-in-law was at the barber’s. As always, no fair looking it up.
Under what condition is the American flag *not *flown at the Whitehouse?
The flag is not flown over the White House if the President is not in D.C.
That’s correct. And bonus points for being quick about it.
I’m full of useless knowledge. No comments required. 
I’m just glad the myth about burning the flag if it touches the ground was cleared up for me recently.
You’re supposed to burn the person who let the flag touch the ground.
nice…
" The flag is not flown over the White House if the President is not in D.C. "
Same rule as for the Queen of England - the flag flies over Buckingham Palace when she is there.