If you lay a Neoair on a reflective layer, the two will quickly become the same temperature. It won't matter what the reflective property of the layer it is sitting is since the radiation exchange is occurring inside the mat, thus only the reflective properties of the mat matter.
I think you're wrong about that.
What is relevant is how much radiant heat is passing through the neoair layer and if any of it can be reflected back inside the NeoAir by the bubblefoil layer.
The bubble foil reflects about 96% of radiant heat. I've looked at the reflective material on a NeoAir and I doubt it achieves that efficiency. It just not near as reflective. That's what I based my assumption on when I said placing bubble foil under a NeoAir might add a bit of warmth.
I think I also said it works better if you lay it on top of your pad.
I suspect Neo Air's already use multiple radiation layers inside the pad(at least the new ones)
Since mine is not a new model, that would seem to confirm my observations. The trick for them is getting the reflective layer about 1/8" under the top of the mattress with airspace in between, like bubble foil does. No easy trick, they can't trap the air, the pad won't pack down small if you do that.
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It seems clear to me that how well these non-breathable reflective materials work is a very personal thing, might be somewhat regional and weather conditions based too.
Phat apparently gives off more moisture than I do, and because of that a SOL type layer does not work for him. There's nothing strange about that, we're all a bit different. But because they don't work for him is no reason I should not use them if they work for me.
As I've said, I think the material can be improved, or at least improvised better, for our needs. I even found and linked to a lightweight breathable reflective material that I think should be tested to see if it solves the kinds of problems Phat and others have experienced. I looks to me like it very well could, but I can't test it, I have not been able to duplicate those problems.
If that stuff works, just like it is, not yet optimized for our use, it could potentially lower your bags comfort rating by 10º, weigh less than 650 fill power down to do it, and cost less than $10.
Just because WM hasn't figured out how to incorporate it into their bags yet doesn't mean it can't or shouldn't be used. One reason they probably can't put a reflective layer inside a sleeping bag yet is because it loses its efficiency too fast, the shine wears off of it. But don't think they (and others) aren't still working on it. Whoever figures out how to use it first will have the lightest bags on the market.
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