Which of the following promotes energy efficiency in existing buildings?

Replacing old heating systems with more efficient models is a key strategy for promoting energy efficiency in existing buildings because HVAC systems are often a significant source of energy consumption. Older systems tend to have lower efficiency ratings, which means they use more energy to produce the same amount of heating or cooling compared to newer models. By upgrading to high-efficiency heating systems, buildings can reduce their overall energy use, lower utility bills, and decrease greenhouse gas emissions. This action not only improves the comfort of the building occupants but also contributes to sustainability goals.

While increasing natural light can help reduce reliance on artificial lighting, it does not directly relate to energy efficiency in terms of heating or cooling performance. Renovating for larger spaces could potentially increase energy consumption if larger areas require more heating or cooling. Dividing spaces into smaller units may improve occupancy comfort but doesn’t necessarily contribute to the overall energy efficiency of the building's systems. Thus, replacing heating systems stands out as the most effective and direct method to enhance energy efficiency in existing buildings.