Which method involves installing air-impermeable insulation during roof construction?

The method of installing air-impermeable insulation during roof construction can be effectively done both above and below the roof sheathing. When insulation is placed above the sheathing, it acts as a continuous layer that reduces thermal bridging and helps regulate temperature within the building. This method is particularly effective in preventing air leakage, which is essential for maintaining energy efficiency.

Likewise, installing insulation below the roof sheathing also provides added thermal resistance and helps prevent heat loss, especially in colder climates. This dual approach is beneficial because it enhances the overall performance of the roofing system against air infiltration and other environmental factors.

In contrast, limiting insulation to just below or just above the roof sheathing does not maximize its effectiveness across the entire roofing system. Installing only on exterior walls is unrelated to roof construction and does not contribute to the benefits associated with proper insulation placement for roofs. Therefore, the most comprehensive and effective method involves both locations, making the choice valid.