Pex tubing loose in flooring plates. Silicone vs no silicone

heathead

I have pex-al tubing in panel system that has some space between the tube and the aluminum plates (not a tight fit).  I would think that silicone is an insulator, but is it less of an insulator than air, or  does the pex-al radiate the heat to the aluminum with the air gap.   I see Uponor uses silicone in their quick trak system. Is silicone with a radiant panel going to increase or decrease performance.  Are their any other products that might work better, or is it all a mute point.   Thanks

NRT_Rob

if it's a loose fit

make it a good fit any way you can. silicone is much better than air.