Besides good roof detailing and watertightness, the performance of the assembly depends on a combination of adequate attic venting and airtightness of the ceiling.

In this assembly, the roof sheathing is at risk of condensation and fungal growth due to night sky radiation. An anti-fungal surface coating should be used to reduce this risk. For additional information on this, see the Attic Ventilation and Moisture Research Study published by BC Housing.

A service cavity at the ceiling will reduce the number of penetrations in the ceiling air barrier and improve its airtightness, and can also be a place to put addition insulation.