Any one of several things can happen since we are getting close to the melting point of the aluminum. At the very least it will deform and maybe fall off. It will certainly oxidize rapidly, which will result either in it turning to powder and falling off, or it could catch fire and burn away. The rapid oxidation may produce enough hydrogen to burn, and that may cause it to reach its melting point. So it really is not possible to know for sure what will happen.
But let’s assume we pick a lower number so that the aluminum foil retains its original physical configuration. Let’s also assume that the hot gas flow is the same and we will ignore any burning hydrogen shed by the aluminum.
Now the convective heat transfer in the two cases will depend upon the convective heat transfer coefficient. Without testing it, I don’t know the numbers for sure. But most likely the coefficient is higher without the foil, so more heat will be transferred to the brick in that case and it will get hotter.
We also have radiant heat transfer from the flame. That will be higher without the foil, so again the brick will get hotter.
Any heat that gets transferred to the aluminum covered brick will have to conduct through the aluminum, which will provide a small amount of thermal resistance, slowing down heat transfer to the brick. So again, the brick gets hotter without the foil.
So for this temperature assumption, all modes of heat transfer result in a hotter brick without the foil.
Edit: I'm used to working with flames that are between 2300 and 5000 degrees F. So that is why I was asking the question. But after thinking about it, a common burner is sucking combustion air in at a low rate via natural convection, so the flame temperature will be much less than my flames that are fed by huge air compressors. Also, in the ten inches above the flame, much ambient air will be drawn in, further cooling the flame exhaust gas. I'm guessing that actual gas flow temperature at the brick would be in the neighborhood of 500 degrees F, unless you did something to prevent exhaust gas dilution.