Looking at the side view here there are lots of not needed points that can be joined.
All the straight lines between windows and floor can be optimized away without sacrificing anything.
The lines are from details in the front but there is no need to have all this detail on the sides.
Uppermost section of the front, the lower straight line has lots of points that does not do any good for the model.
Same thing with house for the roof mounted light.
Do you use creasing in 3D Canvas? Same as smoothing groups in 3d Studio. Shading of texture that allows a smooth surface with less polygons.
Getting a nice curved surface without creasing is difficult and takes lots of polygons.
