Estimates of how different tubing materials can affect the thermal performance of a radiant slab.
For as long as I have been involved with hydronics I've heard "discussions" on how the type of tube used in a heated slab affects performance.
One camp usually points out that the thermal conductivity of copper tubing is more than a thousand times greater than that of PEX. To the thermally uninitiated this might suggest that using copper tubing in a radiant floor slab will yield one thousand times more heat output. I'm sure many of you can picture Joe Homeowner in wide-eyed amazement when such a statistic is tossed out during a sales presentation.