Which indoor factor can negatively affect the performance of a heat pump?

Air leaks represent a significant factor that can negatively affect the performance of a heat pump. When there are gaps or cracks in the building envelope, conditioned air can escape, resulting in increased energy demand to maintain desired indoor temperatures. This loss of efficiency can lead to longer operating times for the heat pump, reducing its overall effectiveness and increasing energy costs.

In contrast, elements like the proximity to windows, high ceilings, or the presence of furniture may have some impact on airflow and distribution of heated or cooled air, but they do not contribute as directly to the loss of conditioned air as air leaks do. While windows can introduce heat loss through conduction and high ceilings might lead to stratification of air temperature, air leaks facilitate a more significant and continuous loss of energy that directly undermines the heat pump's efficiency and performance.