On Wed, 4 Aug 2010 08:54:25 -0700 (PDT), jamesgangnc
wrote:

On Aug 4, 11:46Â*am, wrote:
On Aug 4, 9:13Â*am, Yong Huang wrote:

Thanks. More than half the time at night, the AC is not running. I
hope the room is not too warm during that time. I'll try to put more
insulation in the ceiling above this room.

That will make it WORSE by trapping the heat that is rising up from
the driveway below!

No, it won't. The room is already conditioned space. It is not
conducting heat from below the floor, thru the room, and out the
ceiling.

Improving the insulation below the floor would be more effective but
I'm assuming that space is unaccessible from above or below without
major demolition. In most cases the space above is easily accessed.
Improving the insulation up there, while not as effective, would still
reduce the overall heat transfer between the room and the surrounding
unconditioned spaces. Anything that does that will reduce the load on
the hvac service to the room.

Is it possible you don't know what you are talking about?
It is almost ALWAYS possible to insulate a carport ceiling, one way
or another - and it WILL be more effective than insulating the ceiling
(which could very well already have been done) The difference in
temperature is due to the heat radiating from the driveway - so the
only way to attack the problem is to reduce the amount of that heat
getting into the room.