The fastening devices must reach through the insulation and into the wood to prevent the tubing from floating up as the concrete is poured. If a wood floor is to be placed over a slab, sleepers are used to create a space between the wood and the slab deep enough to fit the tubing on top of rigid insulation. At least one inch of rigid is needed, and two is better. Wood has nearly the same R-value as insulation, and if the tubing is sandwiched between two materials of equal insulation values, it will lose heat equally in all directions, including the slab and into the soil below it. There are times when it is impossible or next to impossible to get enough tubing in the floor or baseboard along the walls.
Alternatives are floor mounted recessed units or free standing radiators.
With central air almost the norm in new construction, ductwork is inevitable. Hot water is required for the radiant anyway, so adding another circulator and feeding the air handler isn't a big deal. By using a two stage thermostat, the radiant loop can be the first heat call, and the ducted the second. This design keeps the radiant as the priority heat source, and the warm air as an assist. Air rotation creates the opportunity for a central humidifier and improved air filtration by using a high performance air filter or electronic air cleaner.