Your fan/inlet arrangement is correct. The 16 inch fan may be a bit of overkill however. The recommended one complete air exchange per minute in a 9 x 12 is about 800 cfm. The unit you mention is 2000 cfm

Sounds like you are on the right track :)
One thing I could not live without in my greenhouse is the watering system. We use a lot of drip emitters into trays that the potted plants sit in (I use dog kennel liners for trays and they work great!). Each emitter line has an on/off valve so if a tray is empty it doesn't get watered. I have a couple of different zones set up and use a timer (like is on a yard sprinkler system) to auto water my plants daily. I also set up a zone outside the greenhouse where I hold plants that have outgrown the greenhouse awaiting to be planted out. The timer allows me to set the time of day and how long to run the timers. It takes some toying with to get the amount of water right but was worth every penny.

I live in coastal Northern California, with much the same temp range you mentioned. I built a wood framed 9'x14'and used TWO 16" shutters for intake and a gable mounted 16" fan for exhaust. The numbers may be "overkill" but I've never been sorry about going to a higher than calculated air movement scheme.

I've forgotten the amount I might have saved by going with a smaller (and perhaps adequate exhaust fan)...I run mine on a speed control....mid to low setting in the Winter and Spring, and higher speed setting in the Summer.

The orchids LIKE air movement.

My two cents,

Steve

I life in No. Calif. We've had temp to 110 on and off for 2 months now. My husband put a 16" attic fan in our greenhouse, it's definately needed. My door is a screened storm door, and I open the window during the summer. I have a stand mister in front of the door, and that fan pulls enough air through, past the mister to keep the temperatures down

THANKS!!!

Here is some clarification:

The floor will be 9x18, not 9x12. The mail reason I was thinking 2000cfm when less would do is because of the extreme moisture in the air here with fog rolling in on virtually every summer night. Does that make the requirements seem a bit closer to 1500cfm or so?

I can't wait to get it finished.

The whole idea of air exchange once a minute is good and it's a common practice, but my experience is that this is not sufficient for high intensity sun and single layer glazing. I installed multiple additional vents to get natural ventilation going before the fan kicks in.

I want to grow vegetables to save money, have more variety and better food, but I don't want to be paying for it through higher electricity costs.

Venting is done with a fan and vent for most of the year, and then I am relying on manual venting for the summer.

Since you are building this from scratch, you also have an opportunity to install underground heating with Pex piping. This can be coupled with solar panels or a water heater of some sort. This type of feature is installed in all three of my greenhouses, and it makes a big difference in getting a jump on the season and extending the season.

One concern I would have is installing overhead glass. It's heavy and potentially dangerous. Have you considered glass walls and a poly roof?

Clair

Here is a link that might be useful: Shop converted into a greenhouse

Thanks for the input, Clair, very informative also.

The glass is tempered, 1/8th inch, and will have support purlins on the trusses that the glass will sit on.

Poly would be a great idea, but want to keep this cheap as possible :)

I've very slowly been working on it, here are some photos so far

Here is a link that might be useful: Greenhouse progress