Which factors contribute to heat gain in a building?

The correct choice identifies the critical factors that significantly influence heat gain in a building. Windows and insulation quality play a central role in regulating how much heat enters or escapes a building.

Windows can vary greatly in their energy efficiency; single-pane windows typically allow more heat to pass through compared to double or triple-pane windows that are designed to reduce heat transfer. Insulation quality is equally important, as inadequate insulation can lead to substantial heat gain during the summer months. Proper insulation helps maintain a consistent indoor temperature by minimizing heat exchange with the outside environment.

While the other factors mentioned may have some impact on energy efficiency or HVAC performance, they do not directly address the mechanisms of heat gain the way windows and insulation do. For instance, the type of ductwork can affect the distribution of conditioned air but does not influence the amount of heat entering the building. Similarly, while the color of the building can affect thermal absorption, its impact is often less significant compared to the role of windows and insulation. The orientation of the HVAC unit is more about efficiency of the system rather than contributing to heat gain.

Therefore, focusing on windows and insulation quality gives a clear understanding of how they dictate the heat dynamics within a building.