It's also possible to fasten the tubing and aluminum heat dispersion plates against the bottom of the subfloor. Below floor tube and plate systems work well when raising the floor level is not an option.
The plate cradles the tubing against the subfloor as well as disperses the heat across the floor to avoid objectionable variations in floor surface temperatures.
The ideal installation conditions for this system would be completely unobstructed floor joist cavities. However this is often not what the installer has to deal with. In some cases, plumbing, electrical, ducting or other utilities may already be routed through the joist cavities. This could make access to the underside of the subfloor difficult or even impossible.