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!)

The method you describe is a carry-over from heating crawl-spaces in the extremely-cold areas. The idea is not so much to heat the floor above entirely, but to temper the area so it is not near outdoor temperatures.

Install a damper in the duct that supplies the air. Then you will be able to see the result of closing it off in the winter - without totally abandoning the idea if it proves necessary. With foam on the underside of the floor the air to the space will be less necessary for a comfortable floor; but without the air the ducts would get such cold air in them that the blast of cold air from the ducts when the blower starts again (if it is not constant flow) would sure make a bare-legged cook jump.

Underfloor radiant heat would get rid of the heating problem with much less wasted energy; but you have what you have. I imagine you are enjoying the hydro-electric rates there, so electric radiant heat would be easy to install and as much to run as any fuel.

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The Senate and House can not find a suitable health plan for the nation; they should open their own exclusive health plan booklet and start reading.