Page 3 def. 13 of the WI Administration Code. See full Code in link below.
(13) “Group child care center” or “center” means a facility where a person for less than 24 hours
a day provides care and supervision for 9 or more children who are not related to the provider. dcf.wi.gov
Links: dcf.wi.gov

In addition to the brief (but correct) summary below, there is a difference in the quality of heat provided by many direct vent fireplaces. The venting flexibility is far better than what people traditionally think of vented fireplaces (wood-burning and b-vent gas), which must be vented vertically and actually suck heated air out of the home through the vent system.

Better quality direct vent fireplaces are sealed with ceramic glass, which not only makes them safer (high impact resistance) and better looking (low glare glass), but also make them more efficient, radiating more heat into the room.

The radiant heat can make a big difference in a room with a tall ceiling, where the primarily convective heat from an unvented fireplace would rise directly to the ceiling. Radiant heat travels as sub-visible light, just like the heat from the sun, gently warming objects all around the fireplace.

One other advantage of direct vent technology is flexible venting options. The vent may terminate horizontally (in a side wall) instead of going up all the way through the roof, which can mean significant savings on installation ($500 or more in some cases). Direct vent technology also allows large vent offsets with 90 elbows (up to 15' horizontal runs, typically), which make them easier to add to homes that were not designed for a fireplace originally.

There is also a MUCH wider selection of direct vent fireplaces than unvented fireplaces, which are sort of a "niche" product.