To support tile, you need deflection to be at least L/360 for tile and L/720 for stone. This measurement is a combination of joist size, spacing, and span. Google "deflectolator" for a calculator that will calculate yours. If the rating is insufficient, you can add or sister joists to reduce deflection. Then you need underlayment. Tile needs 1 layer of plywood (OSB is ok); stone needs 2. Then the substrate: Ditra is best, as it's a decoupling membrane, plus way easier to install than cement board. We just put fiberglass batts in our bathroom floor/garage ceiling, and we have radiant floors. As for the upscale look, it's not just about the size of the tiles, it's about material and layout. So come on over to Bathrooms when you're planning your materials, and we can give you feedback on your choices.

Have you considered a hardwired in-wall/ceiling heater? Timer/Thermostat/Control could be anything you like, a programmable line voltage model could work great for you. We have a wall mount in the master bath hooked to a simple 30 minute timer. Works great and no cords, the only downside is they cost about $80 online.

While I'm sure between the husband and dog we could heat the whole house with farts, they're too smelly and hard to collect. We've found out the joists run in a favorable direction to remove one radiator and run the pipes under the floor, leaving one. We also purchased a heat light as suggested above. I can only find one place who I think stocks the floor warming mats in my area. I can't believe there aren't more, so if anyone knows someplace in the Chicago area, NW or W preferably, please let me know. The Heating guy is coming Monday, and the electrician and GC will be back Tuesday.

"will underfloor heating help warm the room at all, or just stop the floor being chilly?" A true underfloor radiant heating system will heat the room. Basic under-tile heat mats or cables can do what the others' wrote; simply warm the floor, or some are capable of warming a room. "2. what wattage of towel heater is needed to make a difference to air temp? Over 150? Over 400?" Look at the BTU output. Most "towel warmers" struggle to simply warm towels. If you want a "towel warmer" that will heat a room, look at Runtal. There are other brands as well. Some of their warmers are hydronic, some are electric. For room heat, a very generic rule-of-thumb...which is exactly, that...a generic rule-of-thumb... recommendation would be to get something that can output about 25-30BTU per sqft of room. You have a 10' x 10' room, 100sqft, you'd look at a unit that can output 2500-3000BTU. There's always Manual J for a more accurate number. "3. whats the most energy efficient and non-ugly ;) way to heat a bathroom?" First, stop the loss. Air seal the room to prevent air infiltration through the house's thermal envelope, and properly install whatever insulation that you use. Then address heat requirements. In a light-use climate like yours, anything "radiant floor" you'd want low-mass for quick response times. Simple under-tile cables or mat systems, or if you did go with a true underfloor hydronic, a low-mass staple-up system would probably serve you best. If you pursue the towel warmer route, Runtal and Runtal-like towel warmers come in a variety of sizes (BTU outputs) and styles. They blend well with most decor. Most cost-effective would likely be a Runtal-type warmer with a few judiciously placed bathroom floor rugs set on the tile.