Baseboard Radiant heat, want to add underfloor heat for bathroom

TheHox

I have a traditional boiler system, with baseboard radiant heat. It is a 4 bedroom house, and the heat is setup for 3 zones.



Zone 1 is master bedroom

Zone 2 is 3 other bedrooms and bathroom

Zone 3 is living room/dining room/kitchen



The bathroom is where I would like to install some pex underfloor heat. What would be the easiest way to get this to work? Do I have to create another loop for the bathroom with a mixing valve? Would I create a 4th zone? Or just a seperate loop with a mixing valve that would come off the 3rd zone.

Thank you for your help!