Where should screened slots or ventilating units be installed in a closed or boxed cornice?

The installation of screened slots or ventilating units in a closed or boxed cornice should occur at the soffit. The soffit is the area beneath the eaves of a roof, and it plays a crucial role in promoting proper ventilation for the attic space. By placing the ventilating units in the soffit, airflow is allowed to enter through the eaves and circulate through the attic, which helps to regulate temperature and moisture levels. This is important in preventing issues such as mold growth and ice damming in colder climates.

The other locations, such as fascia, rafters, and gable ends, do not serve this specific purpose as effectively. The fascia is primarily a decorative and protective board at the edge of the roof, while rafters are structural elements that support the roof's slope. Gable ends refer to the triangular upper part of a wall that supports the roof, which does not provide the same access for ventilation as the soffit. Therefore, the soffit is the optimal placement for ventilating units in a closed or boxed cornice.