Carriage considers the living area and basement area as one big compartment. This can be a good thing or a bad thing, depending on what you store in the basement and how much space you want to pay to heat and cool.
In extreme cold conditions, it keeps your basement and associated holding tanks from freezing. In really hot climates, it keeps the items in the basement relatively cool. However, the trade-off is that you must heat/cool the extra space of the basement. And, the outside compartment doors don't provide much insulation value.
I closed off the vents in the floor going to the rear basement just so I wouldn't have to cool that area last Summer.
I agree that it is kind of tacky looking in the utility areas below the sink and lavatory.
