Product Focus: Radiant Heating Systems Issue: 9/01 The framework of a Wirsbo Radiant Floors heating system is our flexible, resilient, Engel method cross-linked polyethylene (PEX) tubing. Wirsbo hePEXplus is heat transfer tubing with an EVOH oxygen diffusion barrier. AQUAPEX is our potable water tubing, but it can also be used in hydronic heating applications where the system contains no ferrous corrodible components. Wirsbo PEX is durable, corrosion resistant and has a life expectancy of over 100 years. Wirsbo.