If your floor insulation is FG batts, I'd recommend pulling them, friction-fitting 2" of XPS insulation between the joist bays right up against the bottom of the subfloor, then re-installing the FG batts.

Instead of friction-fitting the XPS, you could cut it slightly narrower than the joist bays, tack the XPS in place, then use canned foam to fill the gap between the XPS and the joists.

Use XPS in the rim joist as well. Probably take three sheets, maybe four depending on the rims. About $35 a sheet.

As for the room heating? One of the best radiant panels out there is the Runtal Omnipanel. It can be a towel warmer, a clothes dryer, and a room heater.

They come in various sizes but one of the the 2400BTU models should work well for you, giving you roughly 30BTH/hr/sqft.

No personal experience, but you might consider a towel warmer. Apparently some of them will help warm the room. There are some threads about them on here, linking one below.

Here is a link that might be useful: GW thread on towel warmers

Another vote for a towel warmer. The Runtals are not cheap but they do the trick

My tile installer told me about a new heated tile floor product from Schluter that will only radiate heat upward not downward; we are waiting for it to be available this spring before we redo our downstairs (concrete slab) bathroom.

I would look into why you are losing heat, not a very big room. You could get an eheat electric wall heater.

Here is a link that might be useful: link

1 heat run should be sufficient for an 8x10 bathroom if it is done correctly. I am guessing forced air furnace? I would check that you are getting the correct amount of air moved into the room first ( you could check with a meter or just compare the diameter of duct to the other runs in the house. looking for leaks as you compare) Then ensure the attic and walls are both correctly insulated. Next I would address the floor by insulating the perimeter wall and box sill of the crawl space rather than doing anything different with the floor joist batts (make sure your crawl space vents are closed during cold months - sometimes forgotten about). A good number of times I have seen plumbing access holes cut into the floor underneath the tub not get sealed correctly, even no insulation behind shower wall is quite common - plumbers, electricians and most home owners frequently disregard the importance of thermal breaks, insulation, and ventilation during their projects. If you have vinyl siding, lift a row on each wall and drill an inspection hole in the wall pockets to see if there is any insulation. IMHO an 8x10 bathroom insulated well with proper venting and decent duct work is all that you need before installing any additional heat source. There is a reason the room is cold and that needs to be addressed first, call a local insulation contractor. The good ones will do free estimates, make certain they explain what work needs to be done and take it from there.

We've used one of these for years in two different houses. They done take up a lot of space and work well.

After the remodel, reinsulating walls and ceiling and adding radiant floor heating we no longer needed it. The floor heating adds plenty of additional heat for our bathroom.

Here is a link that might be useful: Heater