I am still in progress of getting my set up done but here is what is done/or will be.  The basement floor heat is done with the electric boiler floor heat on it's own zone.  The garage floor manifold zone is fed by a large source and return line to main boiler.  I have forced air off peak electric heat with propane backup in main house, that system is set up with ducting to heat the whole house including basement so floor heat in basement is not only heat source.
I then put in a water to water exchanger in basement for the third zone. From the water to water exchanger I have the large source and return line heading to the manifold area in garage for the apron and sidewalk heat.  I do not have the concrete pourded yet so not using that part yet.  The design of that circuit is to set up that outside zone in a priority electric circuit so when I "punch" the outside heat button, all the heat will go there for that predetermined time.  The outside zone is also seperated by a water to water exchange due to the different antifreeze mixture in that circuit compared to the houe system.   I do not plan to have outside heat on all the time, it is 20 below right now, I just want it for ice removeal at times.  The antifreeze mixture for that low of temps is not as heat transfer effecient as what is used in teh rest of the house.

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