Insulating between recessed basement trusses – GreenBuildingAdvisor

The foundation of our home was designed with a reverse brick ledge that the trusses sit into to allow our main floor to be at the same level as the top of the stem wall. The trusses are spaced about 1/4” away from the stem wall so the truss wood doesn’t come in contact with the concrete and the brick ledge has a capillary break tape that was installed prior to placing trusses on it. My question is, how to insulate this space? Or, does it need it due to the way we’ve designed the exterior?

The exterior of the stem wall has 2” of foam, the sheathing and walls are made to line up with where this 2” ends. The joint between the sheathing and foam is air sealed first with closed cell spray foam to fill any exterior gap and then taped with siga fentrum 9” around the entire exterior. There is no exterior insulation on the sheathing but the walls are 2×8 thick with Rockwool insulation and intello vapor barrier. 

With this set up, do we need to insulate the basement truss space since they are recessed and in a conditioned space? Or do we need to do something to fill the 1/4” air gap and between the trusses?