Which insulation method is characterized by the installation of air-permeable insulation?

The installation of air-permeable insulation, which allows air to pass through, is best characterized by its placement above the roof sheathing. This location is significant because it helps to manage moisture and improve ventilation in the attic space. When insulation is installed above the roof sheathing, it acts as an effective barrier against heat loss while also permitting the flow of air that can help reduce the chances of condensation forming in cooler temperatures. This method is generally used in ventilated attics where maintaining airflow is crucial for the health of the roof structure and the entire building envelope.

Placement below the roof sheathing does not align with the characteristics of air-permeable insulation since it typically involves closed cell insulation, which does not allow airflow. Similarly, installing insulation only on exterior walls does not ensure the same benefits of managing condensation and ventilation as the method above the roof sheathing does. Covering insulation throughout the building envelope might also involve different types of insulation materials and methods, which may not specifically cater to air-permeability. Thus, the most fitting option for the question about air-permeable insulation is the installation above the roof sheathing.