I would agree with the HVAC guy, an electric in-floor mat would likely be the least expensive, easiest to install, zone and control. It may also represent one less trade involved in the renovation.

Depending on construction techniques, an in-floor electric mat may have the lowest physical profile of any in-floor heating method representing the smoothest transition in terms of âÂÂstep-upâ elevation from one area to the bathroom compared to in-floor hydronic. Therefore, electric radiant may reduce the âÂÂtrippingâ factor of stepping into the bathroom if the heating medium were to be imbedded.

As the product linked to below incorporates an EMF canceling design technique, there is little reason to reject this method from a health and safety point of view.

SR

Here is a link that might be useful: SunTouch

Assuming that there is a vanity, have they considered a toe-kick space heater?

I suggested a toekick heater - nope. Also electric radiant - nope. Even a towel warmer (radiator) - no. They want the hydronic radiant quote first.

Supposedly another contractor says he can use the existing radiator pipes, but I can't find anyone to support that.