Air Conditioning Advice Needed

get a white roof (either duro-last, foam, or white crushed rock), install a hard surface floor, create a cross breeze, and plant trees in strategic locations.

If you don't want to go that route, please don't mount an AC unit on your roof! They look hideous! Look at ground mounted system so you can hide them!

Saw a great Garage AC unit being installed today in Rancho San Miguel on Santa Fe in conjunction with an Abril Foam roof. Looked like a great way to go with only the low profile ducting up on the roof under some sprayed foam.
We have an AC unit on the roof way at the back of the house that was installed by the previous owners. You can't see it from the street but I sure would like smaller ducts.
As we are out in Walnut Creek with small kids, the summers are Hot and I could not see living without the AC.
Good luck to you and call the Abril folks about this Garage unit.

Susan: there are several discussion threads on A/C during the past 10 months. As a new comer to CA. and the South Bay, I suffered through last year's heat wave, the current heat wave and annual once-every-decade heatwaves. Of course, there are "naturalists" and A/C advocates, and the opposing opinions they hold are very strong.
My suggestion is to work through a list of options - - not by coincidence, the naturalist (shade) methods are inexpensive while the A/C route is the most expensive (but you get immediate relief time-and-time again).
(1) Outside shade via fast growing trees, etc. -- anything to block the sun's rays from hitting your house. The shade people have ideas about this.
(2) Inside the house, window treatment or sun blocking glass.
(3) An insulated foam roof - - this really makes an measurable difference, but if your roof is fine, you wouldn't spend $15,000 when A/C relief can be had for $6,000. However, if you need a new roof, you can consider the UNICO system which is a mini-duct system protected by a new roof - - I'm not certain a new roof is mandatory with UNICO, but the ductwork needs to be protected and the UNICO system itself requires poking holes of about 3" in your ceiling. Anyway, one posting said he got an estimate of $30K!! for a new roof & UNICO system.
(4) Recently, there was a discussion thread on "swamp coolers" (evaporative coolers??). I don't know anything about them, but you can research it as some people say it works well.
(5) Whole house fan - - with a flat roof, it is not a typical Eichler appliance. The previous owner of our Eichler put one on the side of the garage, and it makes a difference (in our BR area) whenever outside air is significatly more comfortable than inside, for example, after 6pm or after sunset. The drawbacks are droning noise (you and one side neighbor), and little relief during the day (and in our case, proping the garage entry door open) - - but this is our ONLY cooling.
(6) A/C -- your choices are (a) window or through-the-wall room A/C units, (b) UNICO (as mentioned above) and (c) mini-split or ductless A/C.
(a) Room A/C is a discussion in itself. I toyed with the idea of a through-the-wall A/C unit for my daughter's BR, but didn't like to architectual effects - - but the price is on the lower end of the spectrum (mostly framing the hole in the wall).
(b) UNICO - - there is material out there about this, but with a 4 year roof, I didn't want holes in our ceiling and crossed off this option from my list.
(c) Mini-split - - people who have it rave about it because they get immediate relief. The issue (besides opertaing cost) is cost -- $5,500 to $6,500 for a 2-zone system; more for a 3-zone system. In my case, I would have needed to upgrade my main panel to 200amp service from 100amp (another $1,800); otherwise, running other appliances during voltage-reduction times would have made my existing panel hot and dangerous. There are 2 aspects of this: (1) hardware and (2) location. Hardware should be easy to decide, but the contractor will sell what he wants, always saying this is the best in the market. Mitsubishi is the largest palyer, but Samsung is coming on strong, but other brands are just as good (Fujitsu, Sanyo, Hitachi, Freidrich, etc.) - - it depends on what the contractor is comfortable in installing. I would stay away from the e-bay units (made in China by unknown companies). Do your research by visiting the various manufacturers' websites (Mitsubishi Mr. Slim, Samsung Quiteside, Sanyo Heating/air condition, Fujitsu air conditioning, etc.). (2) Location - - since there are typically 2 wall mounted air ciculating units (2 zones). selecting sites is not easy - - these units work well in open spaces but partitioned rooms present a challenge. Typically, cooling multiple BR's is an issue. Mini-split A/C is also available as a ceiling mounted unit, but they are single zone and generally has more cooling than necessary for the cubic space.

The Unico hardware is fairly exotic, and more expensive. It operates at much higher air pressure than regular systems. The ducts are about 2" flexible tubes. The high pressure requires that the ducts be covered with sound absorbing insulation that makes them total 4". In spite of the high pressure, more outlets are required per room than conventional systems to obtain required air flow. To hide all the ducting, the roof surface must be built-up 4" using foam boards. This is a considerable expense and requires a lot of labor. The 4x8 foam boards must be cut to fit around the ducts and whatever else is being hidden. A 1 1/2 to 2" thick foam roof is installed to waterproof and insulate (and hide) all this. Eichler owners that have installed this system are quite pleased with it. This eliminates the maintenance required on exposed ducts, which can be a headache on old or poorly installed systems. When the roof is not widely visible, most owners that install A/C or heat and A/C opt for exposed ducting because it is a lot less expensive. If the layout of the Eichler allows it - we encourage buried rectangular ducts that are arranged like a backbone with smaller ribs. The buried backbone (largest ducts) goes down the middle. This helps to eliminate standing water where the structure has sagged. This also eliminates maintenance on the ducts and leaking ducts. With our thousands of Eichler foam-roof customers, very few feel they need A/C after experiencing the difference the roof makes. There is no thermal mass inches above your head, soaking up the heat (or cold) and radiating it inside. Cooling requirements are much less than without the insulating foam blanket. One of our biggest problems with A/C contractors is this: They usually oversize the capacity for the cooling load that 'used to be required'. A/C only works well when allowed to run long enough to dehumidify. Cold, damp air is undesirable and uncomfortable.

You should be able to find the past strings on this topic by doing a search.

We installed a 2-zone Samsung system last spring in our 1530 ft^2 flat-roofed courtyard model and it is terrifc-IMHO. Quiet, effective and can be installed w/o roof penetrations (a biggie for us) --AND worth every cent. I wish we had known about these earlier -- it would have saved us cutting into the walls for those old wall/window style units which are noisy and limited in their cooling ability.

We upgraded our electrical panel at the same time, so the cost was more than mentioned above, but it needed to be done anyway, so that was not an issue.

The most effective things we have done--other than the AC unit--to cool the house were:

1) Install foam roof (wow what a difference!)
2) Install double-pane windows and sliders
3) Install lawns in front and back (got rid of all the wood chips and rocks that the other owner had) - provided a surface to absorb the heat

Cathye