Re: How can you cool/vent the rigs in a garage?

As much exhaust as you can stuff in there. Don't even consider cooling until you've done all that you can with the exhaust side. Then, if you want to run AC to drop the miner's intake air temps, so be it. I'd recommend an evap type of cooler rather than an air conditioner, far less amperage diverted.

Ive been looking at dual zone split acs they have a rediculous 22 ser rating
can cool up to 24k btus and cost only 2300 or so.

wattage is 1600 very reaonaable and you can get a heating and cooling model
which helps with humidity in the winter.

https://www.ebay.com/i/332395637591?chn=ps&var=541410197174&dispItem=1&ul_ref=http%253A%252F%252Frover.ebay.com%252Frover%252F1%252F711-117182-37290-0%252F2%253Fmpre%253Dhttps%25253A%25252F%25252Fwww.ebay.com%25252Fi%25252F332395637591%25253Fchn%25253Dps%252526var%25253D541410197174%252526dispItem%25253D1%2526itemid%253D541410197174_332395637591%2526targetid%253D441940624444%2526device%253Dm%2526adtype%253Dpla%2526googleloc%253D9019664%2526poi%253D%2526campaignid%253D1058340450%2526adgroupid%253D52757731435%2526rlsatarget%253Dpla-441940624444%2526abcId%253D1133886%2526merchantid%253D115324784%2526gclid%253DCjwKCAjwhcjVBRBHEiwAoDe5x8TVwIG03kgWbxkbnR0AW58ZfFkI7ZJ7xmvkzpK1n5O_hhuTCIDPzxoCZAEQAvD_BwE%2526srcrot%253D711-117182-37290-0%2526rvr_id%253D1474104211920

I don't know what cards you have but if for example you have 30 GPU @ 200W each that is 6,000W, so (not even counting PSU & CPU heat) you will need 20,500 BTU. The remaining 4k BTU that you're talking about will probably barely cover your PSUs, CPUs, etc. In the end you're best case stuck with ambient temps in the room.
If you find a way to exhaust the heat to the outside then you will only need a small AC unit to cool the room.

In the past I used one of these 14k BTU @ 10.8A, and had external intake & exhaust so in an 27c room it would pump out 16c air all day long. https://www.amazon.com/Whynter-Dual-Portable-Conditioner-ARC-14S/dp/B0028AYQDC

yeah I alaready have an external exhaust, I have six atttic fans. I will be installing an intake fan next week. The AC is just to help like you said cool the hotspots and add a few degrees of lower temps.

Plus it can help with humidity build up