yes select the room! Only works on polyys convert nurbs into polys later, make sure your normals make sense
then run
computePolysetVolume
take up the number
select the objecsts in the room and run
computePolysetVolume
calculate seconValue/firstValue
Now inorder to automate this totaly youd need to modify the computePolysetVolume script a bit! to return numbers
Note if the room is inverted so thet the faces are inwards! then maya will compute a negative volume no prob just forget the negative sign
If your walls have thikness then maya will produce the volume of the walls! not the room so you should prepare a object thatt describes to room not walls.
Works atleast in maya 7 6.5 and 6 might work on older mayas too