2 4 inch holes on street side bottom of TM?

Would someone please tell me what is the purpose of the 2, 4 inch holes on the streetside bottom of my TM? They are located about halfway between the two windows in front of the wheel near where the eletrical goes up thru the TM floor. In one hole is a small fan connected to an white internal hose that runs up either to the bath or fridge? The other hole is filled with electrical wires, the bottom of a gray metal plate or box with other tubing visible. This second holes would seem to let a lot of air- particularly cold air -into whatever cavity or compartment that is there. While both of the holes in my 2009.5 are covered with a fabric screen mesh, I wondered what the second hole is (the one w/o the fan) and wondered if it could be stuffed with insulation or better closed off. The two holes are not necessarily connected but one can see the vent hose running up from the other hole.
Everything else underneath seems to be nicley sealed off.
Thanks.