There are standards, but you must know them or find someone who does. Most often, people count, or measure, where we assume "living space" includes, but, rooms without windows, no heating, unfinished walls, ceilings, floors, no electricity, head-room reduced and other similar items are not considered "habitable". But, because kitchens and bathrooms are found in every home, they are not counted in the house (except Geneva, for some crazy reason)