The design I used is very simple and cheap and you can buy most components right at your closest lumber yard.
I see people are trying too hard to make tube part more efficient by using some expensive materials and insulators like HD foam etc. The water temperature in loop is very low the heat loss is minimal in this area.
I think the biggest efficiency contributor is my control system multizone manifold using outdoor temperature sensor and variable speed pump control. All components are listed in thread before.
Also this system is low thermal mass system it follows heat demand just almost like air furnace. Concrete filled floors are very high thermal mass systems and will work efficiently only if heat demand is stable. We have one day 15F the next day 45F. Concrete floors will be comfy one day and will fry you the other day.
If I were to build this system again I would use high efficiency HWT or boiler as a heat source or WW heat pump. Also I would build arduino control system using flow control sensors and adjustable flow control valves for each loop and speed control for main water pump. This would make system even more flexible and controllable and definitely more efficient
