What feature does the home described in the scenario include to improve energy efficiency?

The feature that significantly improves energy efficiency in residential properties is the hot water radiant heater. This heating system is designed to provide warmth through a series of tubes that circulate hot water beneath the floor or through radiators. This method of heating is generally more efficient than traditional forced-air systems because it minimizes energy loss and directly warms the spaces where people live, often leading to lower energy consumption overall.

In contrast, while solar panels, energy-efficient windows, and high-efficiency appliances all contribute to better energy efficiency as well, the hot water radiant heating system specifically focuses on improving heating efficiency. Each of the other options addresses different aspects of energy consumption in a home, but the radiant heater is particularly relevant when discussing heating methods and their efficiency.