he has got a point (!) Tiles will absorb radient energy from the sun and
re-radiate some of that down into the attic space. Lining the inside of the
roof with tinfoil would reflect some of this back, and reduce convection
currents.

Whether it would make a noticable difference to the rest of the house is
another matter!

Since I am sick of renovating my kitchen I might try an experiment this
weekend