I just bought a 1-story home in central NY State built in 1960 that has a poorly working heating system. Appears to be the original Lennox nat. gas forced air furnace, which still seems to be functioning fine. Ducts are simple channels (unlined/uninsulated) in the concrete slab and when heat is running the flow is very low at the registers and air is quite moist (evidenced by sweat marks and some mold spots on walls of interior of house). Previous occupant (a renter) complained of it being cold, clammy, and expensive to heat.
I tried to run a plumbing snake through from a register to see whether running flex duct would be practical but ducts don't appear to be a straight shot and can't get any further than 6 feet in at any of the registers (~20ft to the furnace). I suspect the designer might have been trying to achieve radiant heating with this set up but I don't think they succeeded.
My question to the forum is whether I should abandon the ducts in the floor and run new ones up through the attic instead? This option doesn't seem all that optimal either though since winters can get cold here in NY, and the attic is an unheated crawl space (granted, I will be installing R-39 insulation on the attic floors). Is there any hope in trying to salvage the in-slab ducts or was it a bad idea in the first place?
Any wisdom about dealing with in-slab ducts (or work-around alternatives) appreciated!! Should I try to salvage this system or abandon altogether and maybe jump to wall-mounted heaters??
Thanks very much.