Date: 2/21/2009 4:44 pm EDT
None of the "wire-type" floor heating systems designed for under tile use get up to 115 degrees that I am aware of. Typically they all will heat the floor to about 84 degrees, which is plenty. The other wire-type systems must be buried in a mortar to create the thermal mass necessary to heat the floor evenly and efficiently.
Quiet Warmth is the Avaire reccomendation and should probably be used but it isn't mandatory.