I am having a dust issue in one room of my house (rancher w/ full unfinished basement). I have replaced the entire duct system, everything is now hard ducted, no panning. But I still get major dust in one room. There are no gaps in the ceiling/wall or wall/floor joints as the moldings are caulked. Only other guess I have is the dust is coming up from the basement through the hard wood flooring.

The subflooring was laid out with 1/2" to 1" gaps between the wood planks then the hardwood laid on top, half a$$ed by the previous owner.

So I want to seal between the floor joists in basement, here are my options I have been pondering:

1. Buying a few cans of that rubber sealer and spray that between the joists below the room that is the problem.

2. Installing thermopan (used for HVAC panning) up tight to the subflooring and caulking the joints along the floor joists and thermopan.

3. Insulating with typical R-30 batt insulation.

4. Insulating with closed-cell spray foam (very costly).

If anyone has any other ideas, please let me know.

Thanks
DM3