My in floor heating is cooling my house in winter. If my water storage tank temp is cooler than my house temp and my thermostat setting is calling for heat, it runs the pumps effectively cooling my home when I really need heat. My geothermal heat pump is on an off peak power connection, so power is not supplied to my heat pump all of the time. Anyone know of a thermostat that will not call for heat if the supply water temp is cooler than my current house temp? Rick

There are variety of thermostat available in the market. There are various options when purchasing low-voltage thermostats. These are the cheapest and easiest to install. A consumer by hand adjusts the thermostat to the temperature he or she wants. 

Use a programmable thermostat that you can set back the temp during the heat pump off times.

Or power the tstat from the HP power. No power to the heat pump, no tstat to call for heat.

Chris

I think Chris is giving the easiest answer. If you want to do this with water temp though the easiest way to go is to set a "go/no go" temperature on the tank itself. Thermostat goes through an aquastat or to a "setpoint" control that will only pass the demand through if the tank is over a set temperature (say, 80 degrees or more).