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A few years ago I converted my stick house to radiant heat. I'm sort of an anal DIY type so I did it myself and had to learn a lot in the process. Here's the short story about what I learned.
We all probably forgot there are three ways to 'move' heat; conduction, convection, and radiation. Insulating a home is an exercise in trying to contain your heat and these three culprits are always at work trying to undo your efforts.
Stick houses, at least modern ones, do a really good job on convection and conduction. Tight houses cut down on convection by stopping air infiltration. They cut down on conduction by utilizing really high R values, and most do nothing about radiation.
To fight conduction takes thick walls; the thicker the better. Trailers can't have thick walls so they opt for fighting radiation while mostly ignoring conduction. The foil stuff is the radiation fighter.
The problem with understanding all this is that R values were developed to provide a way to indicate effectiveness in fighting conduction. It was never intended to indicate effectiveness in stopping radiation. The people who sell it are forced to market the stuff in an "R Value" world so they fudge some numbers up to try to compete with the pink stuff. If you look at the foil stuff it's just bubble wrap encased in tin foil. It is a very effective radiation fighter ( probably 99% effective) but it's conductive strength is equivalent to just bubble wrap; very thin bubble wrap.
R value on the foil stuff is misleading at best and more likely a fairy tale. It's not that the material is no good. It's really good but it's really good at stopping the kind of heat flow we usually ignore.
I don't know how to quantify the relative amount of flows from the three culprits. I just know that to really contain heat you need to fight all three. Stick houses do a good job on two of the three and trailers go a good job on one of the three. It's the only weapon the manufacturers have.
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