i have a challenging home to add air conditioning to. California home in Los Angeles that only has heating now. Here are the facts:

3 floors -- Main level, 2nd floor, and basement level (we do not use but have friends staying there)

Basement has heating unit and intake downstairs. thermostat down there.

Main level - vents come from basement unit

2nd floor (bedroom area) - separate heating unit in very small crawl space/attic. vents to the 3 bedrooms upstairs.

Total SF - around 4700 sf. Our living space (main level, 2nd floor) is about 3500 sf.

Big issues:

2nd floor crawl space too small for new AC unit. we can put on roof deck (which is next to the crawl space)

Main floor vents come from basement heater, not the one we want to add AC unit to

No crawl spaces so we will have to build soffitts

(YES, the builder of this home was an idiot)

We had one AC group in here and they were ready to roll, but the sales guy under-estimated the complexity and they had to return their 6 guys after 'brainstorming' for 4 hours, with all materials and truck and crane in the front of the home.

Another group, AirFlow, has recommended the following:

Main floor: install an American Standard Air Handler in the garage, and run 3 supply air ducts with register. install a return air grill in entry hall (ugly solution).

Second floor: remove attic furneace and install American Standard 3 ton air handler. Run new ductwork properly sized for AC with manual dampers to balance systems airflow.

But both heat pump condensers on the roof deck.

Run both refigerant lines from the air handlers to its respective condensing unit.

install condensate pumps.

use super qulaity R-6 flexible duct of prpery delivery size w/one inch sound dampening fiberglass insulation liner and vapor barrier.

Equipment:

American Standard - looks like Premium unit but not identified

we have also asked for air purifier/HEPA like unit

I'd love your thoughts on configuring this better - or if you think this is a smart solution. AirFlow is the only group to suggest the use of Air Handlers, so i know NOTHING about them. do they work? is this a good solution? The total estimate (not including the HEPA unit for some reason) is around $13,000, plus electrical, carpentry, etc.

thanks!

wes