Rooms are defined as rooms in a dwelling with a size of at least 4m2, including bedrooms, dining rooms and living rooms as well as walled-in, liveable basements, attics and kitchens serving as accommodation. Kitchens intended solely for cooking are excluded, however kitchen-diners are included. Not included are furthermore toilets, bathrooms, corridors, verandas and meter cupboards. Also excluded are rooms intended solely for business use.