Reflectix

I know there is alot of information here about Reflectix but I am having a hard time finding the precise information I need. Question is... When installing Reflectix, I understand you need apprx 1/2" air space between the outer shell and the layer of reflectix. If I do that, it only leaves about an inch or so of space inside the wall, not enough for the fiberglass insulation. How do I cope with this? Can I do the air space, Reflectix, then another air space and a 2nd layer of Reflectix? Overkill? This is driving me apesh@t trying to figure out how to handle this. TIA.