What do you mean by no air returns?

At best 4-5% savings for each SEER increase.

As far as size, I would want to see a properly performed load calculation in writing.

IMO

Tigerdunes,

Thanks for the reply. It sounds like an up-grade to a higher SEER will be well worth it. I take it the 13 SEER is the low end.

On the returns - the newer construction in Fl I have looked at have no duct work in the rooms to return the air to the handler. The only return is one large return going directly to the handler, usually in a central hall or living room area. So the far bed rooms never get the same temperature as the rooms closer to the one return. This must save the builders money.

More return needs to be added for better airflow and comfort.

One large return for a house this size is nothing more than a joke.

Add at least two more with media filter cabinet at the air handler.

IMO