We have an old (1700's) part stone part wood frame house w/ hot water radiator heat.  we have gutted the 300 sq ft dining room, put in new windows found great old wide pine floors.  Thinking about radiant heat only in this room, any concern w/ damage to wood (heat, drying) or lack of comfort b/c of size and retrofit.  We would insulate basement side very well.  Is it ever not enough heat?

You start with a heat load analysis.

You need to find out how much heat the space needs so that you create a system that will work to keep you warm and not just at foot. This is called a heat loss calcultaion. We, like many radiant heating companies, will do one for you. We charge for it but then it's fully credited towards the purchase of the materials you buy. Use this scenerio for your needs.

You will be required to supply the construction information such as exterior wall, ceiling and floor dims, window sizes and design, insulation used in the same places, etc..

Once you have the heat loss, you now know how much heat you need to surpass to keep you warm. With an electric radiant system, as with all, you will need to replace the lost moisture content with some kind of humidifcation system. I would suggest ZMesh under the the wood you want to use. It staples right down on the substraight and you can then lay the wood directly over the top. Nail through it, screw through it, cut wholes in it using a cut out kit and you won't hurt the element anywhere on the grid or add any measurable floor height as well.

Insulate, insulate, insulate!

Good luck!

Russ

there is another way-
the most heat that you can ideally get through a pine plank floor is in the 15 btu/sqft range.
In a 300 sqft floor, thats 4500 btu/hr.
for a pine plank floor, I would ONLY do outdoor reset, continuous circulation.
Leave the hot water radiator and use a 2- stage thermostat to control the floor as the primary, and the radiator as the secondary.

That information might be true with hydronics, but you can get twice that amount of btu's with a low voltage ZMesh system. As with any radiant system, always keep the wood humdified to the mfr's recommended moisture content for the wood.

A btu is a btu. Output is based on the difference between floor temperature and the mean temperature of the room...period.

BillN has a well accepted stategy and one that I haved used and specified often (though I have driven many pine floors well beyond 15btu's/ sq. ft).

I'm not sure about the 15 BTUs/sq ft either. I routinely push wood of all types up to 30 with no issues. Wood floor installation quality is, of course, important.