The best floor type for radiant heating is tile. Porcelain, ceramic, and natural stone are the best tile options because they’re excellent heat conductors, won’t mold or rot if your hydronic system ever leaks, and don’t pose a fire safety in the off chance your heating system overheats like with wood flooring. For radiant concrete slabs, it’s smart to first install a vapor barrier to prevent moisture in concrete and condensation, especially in basements.