It's not quite that simple. You should check out the work that the Radiant research team at the Center for the Built Environment in Berkeley, CA is doing on the subject. They have shown that radiant loads are not the same as typical air loads. I'd suspect that if you are looking to size a cooling system like that, you will be interested in the heat in the floor, the surface temperature of the floor, plus the surface temperatures of the surface that have some sort of view factor to the floor. The load itself would be based on the radiant temperature you expect to achieve in the space, but the cooling that the system can provide is also dependent on that radiant exchange. The E+ engineering reference guide has a good explanation of how they calculate it.

https://www.cbe.berkeley.edu/research... https://escholarship.org/uc/item/9dq6...