If it sounds too good, then watch out; it probably is. There is no practical way, scientifically, to get R-27 per 1 inch with EPS plus alumimum surfaces. EPS gets R-3.5 per inch. Reflective surfaces will provide a R 6-7 WITH a 3/4" airspace. But there are two issues with this statement; 1) foil in contact with a surface will conduct cold right through it-just like alumimum spacers in insulated windows. You need to create that airspace so that radiant heat can reflect back. 2) Reflection of radiant heat is only one of three components of R-values. The others are convection and conduction. Insulation has to address all three. The best insulation is a vacuum. If air molecules can't freely move about and bump into one another, than they can't transfer heat.