Forget all the laying, leveling and setting cement. If your clients want a radiant floor underneath their laminate, simply lay the insulating heat distribution plates on the existing floor, press the heating cable into place, lay the wooden floor directly on top, connect the thermostat, and turn on the heat. The insulating subfloor and a heat-conducting surface ensures optimum heat reflection upwards. Links:
[1] http://www.danfoss.us