What is the suitable area for solar collector to use in underfloor heating?

Question

What is the suitable area for solar collector to use in underfloor heating?

Answer 1

In addition to the previous response, which deal primarily with heat gain of the system, you must also know the heat losses of the structure: insulation, average temperatures (indoor and outdoor), window area, etc.

You must also decide what percentage of the time you are willing to use a backup system instead of the solar.

Answer 2

As stated, your question leaves too many unknowns to give you a sensible answer. The designer must know the location, the amount of cloud cover, use size and geometry of the building,what kind of collector, etc.