The pipe that transfers the heating fluid throughout the floor is the key component of a hydronic Radiant Floor Heating System. Most pipe used in RFH systems has an oxygen barrier which prevents oxygen from entering the system and essentially eliminates corrosion.
In PEX-AL-PEX (FIG.2) the aluminium core is the oxygen barrier. Standard PEX pipe is encased in a layer of polymer to provide the oxygen barrier.
Probably the most important feature of any RFH pipe is stress life. Under ISO (International Standards Office) or DIN (Deutsche Industrie Norm/German Industry Standard) RFH pipe must have a 50 year stress life rating. The stress test is conducted at 95°C (200°F) at 6 bars (100 psi). When transposed to a 40°C (110°F) at 1 bar (15 psi) operating range, a 100 year stress life is achieved.