I have a trilevel house that is about 50 years old with forced air heat and a fairly new furnace. Now that winter is here, we've discovered that there is no heat in the bedroom that is on the ground level (the level that is on a slab with no basement underneath). There is decent heat "upstream" in the laundry room and bathroom, but none coming in the bedroom. The register damper is not closed (actually, there is no damper on this register). Could it be clogged somehow under the slab? Is there a way to fix this without major excavation? The attached photo of the exterior shows the problem bedroom on the lower right, adjacent to the garage, with the window behind a tree.