Functional obsolescence refers to a decline in a property's value due to outdated design features that diminish its utility or effectiveness, often making it less desirable in comparison to more modern alternatives. The example of having to access a bedroom through another bedroom illustrates this concept effectively. This layout could pose privacy issues and may not align with contemporary expectations for residential design, where direct access to each bedroom is typically preferred.
Other choices, while they involve issues related to a property, do not exemplify functional obsolescence in the same way. Outdated plumbing, for instance, could be considered a physical deterioration or maintenance issue rather than an ineffectiveness in design. High operating costs relate more to economic obsolescence, which is about expenses related to running the property rather than its design. Inadequate heating is indicative of a potential maintenance or upgrade issue but does not directly pertain to how the property's layout or design impacts its functionality in a way that is considered obsolete.