This already exists, downvoted and closed questions will usually be removed automatically.

The exact criteria are [listed in this post on Meta Stack Exchange](http://meta.stackexchange.com/questions/78048/enable-automatic-deletion-of-old-unanswered-zero-score-questions-after-a-year):

> Just to formally document the exact policies we have in place to
> remove old abandoned / dead questions, [the Community user][1] will
> delete questions in the following circumstances:
> 
> **If the question is more than `30` days old, and ...**
> 
> - has −1 or lower score
> - has no answers
> - is not locked
> 
> **...or...**
> 
> - it was closed and migrated to a different site
> 
> ... it will be automatically deleted. Internally, these are termed
> "dead" questions (`RemoveDeadQuestions`, or `RemoveMigrationStubs` in
> the case of a migration).
> 
> **If the question is more than `365` days old, and ...**
> 
> - has a score of 0, **or** a score of 1 in case of deleted owner
> - has no answers
> - is not locked
> - has view count <= the age of the question in days times 1.5
> - has 1 or 0 comments
> 
> ... it will be automatically deleted. These are "abandoned" questions
> (`RemoveAbandonedQuestions`).
> 
> These checks are run every week across all sites.
> 
> **If the question was closed more than `9` days ago, and ...**
> 
> - not closed as a duplicate
> - has a score of 0 or less
> - is not locked
> - has no answers with a score > 0
> - has no accepted answer
> - has no pending reopen votes
> - has not been edited in the past `9` days
> 
> ... it will be automatically deleted. These are "abandoned closed",
> and show as `RemoveAbandonedClosed`:
> 
> [![example of "deleted by Community" notation][2]][2]
> 
> This check is run every day across all sites.
> 
> See also: The official ["How does deleting work? What can cause a post
> to be deleted, and what does that actually mean?"][3] FAQ meta post.


  [1]: http://meta.stackexchange.com/questions/19738/who-is-the-community-user
  [2]: https://i.sstatic.net/usHJW.png
  [3]: http://meta.stackexchange.com/questions/5221/how-does-deleting-work-what-can-cause-a-post-to-be-deleted-and-what-does-that