Which of the following could be a sign of poor insulation?

Inconsistent temperature throughout the home can indeed indicate poor insulation. When insulation is inadequate, it fails to properly regulate and maintain the temperature within different areas of the house. This results in some rooms being much warmer or cooler than others, as heat transfer is not effectively mitigated by the insulation.

Good insulation should provide a barrier against heat loss in the winter and heat gain in the summer, contributing to a more uniform temperature distribution. Inconsistent temperature can be a direct result of air leaks or insufficient insulating material, leading to drafts and areas that do not hold temperature as well as expected.

Other options, while they can indicate other issues within the HVAC system or home, are not as directly related to insulation problems. For example, frequent air filter changes often point to airflow issues or dust ingress rather than insulation quality, regular maintenance checks are a part of routine preventive care, and consistently high energy bills may involve a variety of factors, including system inefficiencies beyond insulation alone.