Are they considered non-essential?
Where is this "non-essential" crap coming from? Who is saying this?
That's how these departments determine who they furlough. If the employee is non-essential, they aren't required to operate the main functions of the agency. Hence, non-essential.
In the private sector, this is a routine undertaking when scaling back due to a loss of revenue or a tax increaase. Federal workers aren't demi-gods because they work for taxpayers.
These agencies could probably trima lot more fat to decrease taxpayer burden.
You are just making shit up. You obviously have no idea what this shut down means and what it affects. Yeah essential employees are on furlough. That is what happens when radicals close our government. This isn't standard procedure.