Good question! SIP relies on seamless bond between facing board (OSB) and the core (EPS). Similar to I-beam if there isn't a good continuous bond between the web and flange of the I-beam, the construction becomes unstable.
In principal there should be an option to conceal the pipes inside the core, knowing exactly how much of an impact it is on the actual structural stability, but probably with lots of testing.
Most 'in-floor' heating systems rely on some sort of thermal mass, but not all of them. SIP is very light and won't be able to provide thermal mass, but will provide great insulation.
I guess the best option would be to lay floor SIP panels first, and than lay another thin layer of EPS on top, to provide 'cut-in' space for the pipes, and lay flooring product over.
Some (walls) come with several electrical chases already cut in just behind the outer skin. Would this be more of an integrity breach than that? Also, this would be on the compression side of the virtual flange. I think the trick would be the return loops at the end of the PEX run. I'd probably have to replace the loops with a header...
True. Those wire chases are allowed for in the calculations and limited to one vertical and two horizontals when panels are used for walls. Also those are usually in the middle of the core, to not compromise the bond to facing board. Most SIP manufacturers around the world agreed not to have any plumbing run inside the walls, mostly due limited serviceability. From what I know most suppliers in NZ also avoid having pipes run inside the SIP, but allow penetrations.
If you wanted more than the standard 3 wire-chases this will likely compromise the structure. However, most cost effective floor solution appears to be having conventional timber joists spaced @600mm crs and panels laid on top of joists. It makes for simpler construction and thinner/cheaper SIPs. And in this case, the spans are way less than what panels can handle.
I do think underfloor heating is the absolute winner in all designs. How to make it work with light weight suspended floor is very interesting topic. And since we don't have any thermal mass to work with, the pipes should be as close to the surface as possible, quick response heating. So I always thought below would be best of both worlds.. basically thicker flooring layer... to accomodate surface mounted pipes and finished flooring on top (?)
Forum about SIP structural insulated panels