What effect does air flow through insulation have on its effectiveness?

Airflow through insulation reduces its effectiveness, primarily because insulation materials are designed to trap air to minimize heat transfer. When air moves through insulation, it creates convection currents, which can carry heat away from the insulated space, making it less effective at resisting heat flow. This phenomenon leads to a decrease in the material's thermal resistance, or R-value, because the air movement counteracts the intended function of the insulation.

In contrast, the other choices do not accurately reflect the impact of airflow on insulation. For example, airflow does not increase the R-value, as the introduction of moving air generally diminishes the insulating properties. Maintaining R-value would imply that the insulation can effectively resist heat transfer despite the airflow, which is not the case. Lastly, improvements related to thermal bridging typically pertain to avoiding heat loss or gain through structural components rather than being impacted positively by airflow. Thus, the presence of airflow through insulation effectively weakens its overall performance.