Heat is heat. All heat is heat. If the size is big, it is sufficient as the room's only source of heat in winter. If the size is small, it is as good as any other small heater of the same power. Leave anything on, for a long time, and you will feel it. Just as much as heat from another source. You can say you don't notice it, if it is really small, but its impact is as real as any other heat source of the same power. Heat spreads out. Heat seeps. Heat distributes itself. Heat does not stop moving into colder things. If the floor is warm, it heats the air next to it and everything else next to it too. It is not true to say it has no impact or no effect on the rest of the surroundings. It does heat up the rest of the hosue / structure / room, but only to the extent that its power enables it to do so, which is equal to the impact of anything else of similar power. Am making this point to be sure other readers later don't conclude that for some reason heat in a floor just disappears once it leaves the floor, or that it contains itself to the floor alone. Although it may be negligibly small, it still does warm up other things. It's just power = warmth, like any other heat source. How it gets described in subjective terms later is a variable that we can discuss for ever and ever, but power equals power equals power. HTH -david

Maren- The answer to your question depends on how your house is built. If the garage is not heated, what you need to do is insulate any shared walls it has with the living space. If it's unheated and you only insulate exterior walls of the garage, then heat from the interior makes its way to the garage and is costing you money; exterior wall insulation in the garage slows that heat and money loss down some, but you are still unnecessarily using the heat you want to keep in the living space to heat the garage. Basically imagine your house without the garage: the walls, floor and ceiling that remain are the areas you want to insulate. You want to create an "envelope" that surrounds all sides of the living areas that you want to keep warm. Does that make sense?

it would be easy to maintain the position that those words were appropriate and sufficient. so, any arguing the opposite point of view might end up in a zero sum exercise. the thing brickeyee did was to make it more practical to the end user who has to run with the knowledge obtained. the mental model is slightly altered when one introduces the notion of heat source. ta da. hope you are open minded enough to let it be. -- one thing I wrote wrong in my first post was not saying the heat source could be above the tiles (or below); any heat applied to the tiles.

Sophie, I think that you are too harsh in calling this a vanity project. The poor OP is just trying to learn if this is practical. I know nothing about how parquet floors are put down and their tolerance for adapting to heat and different levels of moisture. Kudos to the OP for looking to save it. Not every little country church has high ceilings. At 1000 sq, I don't think that this is going to qualify as exactly an example of a "high steeple church" as my wife calls some." (She is in the business.) First thing you need to do is get clear on how much heat you can make a parquet floor take. Then you will know how much heat the floor can emit at that temperature. That is a simple calculation for a hydronic heat engineer. Lastly, does that number match your heat losss calculations? Thickness of the wood does not bother me that much. If there is enough insulation underneath the heat source, it is not going to change your heating costs. If the R=value of the parquet is 1.4, underneath is R-30 and the overall R-value of the building walls and ceiling is R-30, where is the heat going to go? What kind of heat to use? That depends on what fuel sources are available. If you have natural gas, you need to have a boiler. Any boiler can make 80 F water, you just need a thermostatic mixing valve. If your structure is amenable to radiant floor at that temp, you will have uber combustion efficiency. Radiant floor combined with some other heat delivery mehanism is going to be uber expensive. Who can afford to install two heating systems? I guess it might be 1.5 since a single boiler could supply both floor and other types of emitters (think cast iron radiators.) Finally, if you can't have radiant and parquet floor there may be more than one way to punt. One way, of course is another kind of hydronic or forced air heat. If your heart is more set on radiant than parquet floors, you could put the parquet to another use. How does a parquet wall or two appeal to you? You could do parquet wainscoating, or parquet trim around windows and doors. How about a parquet ceiling? I've never seen parquet kitchen cabinets, but why not?