The present disclosure relates to insulated building structures. In one aspect of the disclosure, an insulated building structure includes a longitudinally-extending cavity bound by a first lateral surface, a second lateral surface, a back surface and a front surface, the cavity having a cross-sectional area in a plane normal to a longitudinal axis of the cavity; one or more shelves extending into the cavity, each having an occluded area in the plane that is less than the cross-sectional area of the cavity; and loose-fill insulation disposed in the cavity, loose-fill insulation being positioned above and below each of the shelves.