What maintenance activity does NOT improve energy efficiency?

Cleaning the windows does not directly contribute to improving energy efficiency in the same way that the other activities listed do. While maintaining clean windows can enhance the aesthetics of a building and allow more natural light to enter, it does not affect the thermal performance or energy usage of heating and cooling systems.

In contrast, replacing furnace filters ensures that the heating system operates efficiently, as clogged filters can restrict airflow and reduce effectiveness. Weatherproofing doors helps to eliminate drafts, thus minimizing heat loss and improving overall energy efficiency. Cleaning the vents ensures that air can flow freely, maintaining optimal operation of HVAC systems, which also aids in energy efficiency.