Illustration Source: CHBA Manual, Fig.2.9,Pg.24

Some leakage areas within a home are unavoidable and will always occur.

Examples include: vents, drains, chimney, plumbing stacks, etc.

Insulating around these areas will ensure that the leakage area is reduced as much as possible. As an insulator it is important to make sure that all areas that require insulation are insulated or air sealed to reduce air flow. (This is because insulation should not be used around chimneys for various reasons.)