The ceiling joist/bottom chord of the truss space can be insulated using a variety of different insulation types including batt (i.e., mineral wool or fibreglass) or blown-in fibrous insulation (i.e., fibreglass or mineral wool).

With fibrous fill insulations, blown products with integral binders can be used to prevent settlement within the attic. Batts should be used at the roof perimeter, hatches and in any high wind areas.

Attention should be paid during installation to not block the baffles, as their performance is crucial to the adequate ventilation of the attic space. A cost-effective combination of closed-cell spray foam and fibrous fill could also be considered in a flashand- fill application. In this application, the spray foam serves as the primary material of the air barrier. At the roof perimeter, the roof slope may limit the thickness of the insulation. A raised heel truss should be used where possible in order to maintain insulation thickness.