I am remodling a Missouri Farmhouse and am putting in a centeral air and heat but there is not allot of room for duct work to reach the downstairs bathroom that is off the back of the house on a concrete slab. (NO attic there and no room in crawlspace) My thought is to heat it completly with radiant underfloor heat laid in the concrete slab using the extra run off my Hardy. (the first run will be running through the centeral furnace). The bathroom is only 6' by 13'. I think this will work fine but I also wondered if I could also run this line up to my upstairs bathroom to heat it undertile (run between the floor joist) as well but zone them seperatly as to control their temps. Both bathrooms will have tile floors. What would it take to add the upstairs bath on a loop with an exchanger off the downstairs bath's run from the Hardy? Looking for any ideas as this is not my area of expertise.