Retrofit Radiant with No Subfloor

Gea Pea

We purchased our 1930s home a couple years ago and have been renovating ever since. The first year we upgraded the "gigantic" boiler to a Lochinvar Knight with indirect hot water tank. One of the reasons we went to that boiler was that we wanted any home additions to possibly be radiant, zoned, etc. Now as I'm ripping down ceilings to redo wiring on the main house, and I'm considering adding radiant and removing radiators room by room.



The problem is our old house has 3/4" TG pine floors with no sub floors (only double 2x10 16" OC). The floors have lots of characters and do "move" with the humidity. Any fasteners must be < 1/2" and would go right into floor.



So...

* what's the best type of system for this situation?

* should i add something in between the joists to act like a sub floor to isolate the plates?

* can heat source be too close to floor?

* as long as i have even one radiator that depends the higher temperature...do lose the normal energy savings of radiant and it just becomes a "comfort" based decision?

* issues I may be missing?



(I realize I'll be modifying to boiler setup allow for a lower temperature, etc...but I think there's plenty of info out there on that end of things....)



George