Our 8-year-old townhouse has always had a cold kitchen floor. This year we decided to have foam insulation applied to the underside of the kithcen floor, over the unheated garage's ceiling.

In demolishing the ceiling, we have found that the ductwork for the heating/cooling vents in the kitchen floor is installed below the floor joists. This ductwork is suspended in a large space under the kitchen floor, about 3 feet below the joists. The space is enclosed by plastic vapour barrier, with 6-inch fiberglass batt insulation at the bottom of it (underneath the vapour-barrier and above the garage's wallboard ceiling).

Inside the space, as well as the rigid ducts running to the vents in the kitchen floor, there are 2 flexible ducts that open into the space -- one pouring hot/cold air into the space, and the other presumably acting as a return. I should also mention that there are I-beams supporting the exterior kitchen wall, which is cantilevered over part of the garage. The rest of the ceiling is the roof overhang of the garage. This part is outside the vapour-barriered portion of the garage ceiling, and is vented with under-eave soffits.

Questions: are the flexible ducts necessary to the heaitng of the kitchen floor, or is this an inefficient way to do this?? Should I close these ducts before the foam insulation is sprayed onto the kitchen floor and the other ductwork, or leave them in place????? What about conductance of cold inside from the steel I-beams -- would this be a problem that needs to be addressed? (we live in Ottawa, Canada - down to minus 30 in the winter!)