12k or 18k unit sizing garage

Hi,

I have a 20x20 (8ft ish ceilings) woodshop garage with sliding barn doors that do not seal well at all. Other than that, the garage is rather well insulated (apartment on top, insulated walls, and the sliding doors are somewhat insulated as well). I am located in Austin, Texas (high heat and medium/high humidity). I would only be running the A/C while I am working in my shop, but would like to have it dehumidify the space while I am not working to help keep the rust off my tools/machines. I do not need it cool the space to the lower 70s but just something so I am not working in a 90+ environment.

I have gotten three bids so far. Two contractors think I should stick to a 12k BTU unit, but one is pretty adamant that I should upsize to a 18k BTU unit given the sliding barn doors air sealing capability.

I am thinking of sticking to one of 12k BTU unit bids and while also adding some brush seals to the barn doors to help them seal better.

What would the pros on this forum recommend?

source https://hvac-talk.com/vbb/threads/2241151-12k-or-18k-unit-sizing-garage?goto=newpost