Which of the following elements is NOT included when calculating total heat loss?

When calculating total heat loss for a building, factors such as wall area, window area, and door area are directly involved in determining how much heat escapes from the structure. These elements help assess the thermal performance of the building envelope.

The wall area represents the solid part of the building's structure that can contribute to heat loss through conduction. The window area is significant due to the potential heat loss through glass, which can be much higher compared to walls. Similarly, the door area must be considered as it allows for heat exchange between the interior and exterior environments.

In contrast, furnace efficiency does not factor into the calculation of total heat loss from the structure itself. Instead, it relates to how effectively a furnace converts fuel into usable heat for the building. While important for understanding the overall heat management system, it does not influence the physical characteristics of the building's insulation or heat exchange surfaces that are considered when estimating heat loss. Thus, furnace efficiency is not included in the calculation of total heat loss.