The Solar-AC FAQ : Minimizing the need for cooling :
What's thermal mass and why do I want it?
See also: 
Tables of specific and latent heat values
Thermal mass inside a home tends to damp and time-delay
the day-night cycle
of heating and cooling. This can drastically reduce the amount
of active cooling needed. The thermal mass should be INSIDE the
insulated space of the home.
faq@solarmirror.com