Garage minisplit sizing sanity check.

[Arkive]

Built this house last year and I'm ready to further invest into the attached garage to prepare it for some additional hobbies like woodworking, and a minisplit seems like the obvious first step. The HVAC company I've used for years and generally trust recommended a 24000 BTU single head unit. Has anyone conditioned a similar space and think that sounds right for the following specs:

1. 1400 sqft
2. 11.5' ceiling
3. Three insulated garage doors and all walls insulated and double-pane, low-E windows.
4. 1/4 of walls and the entire ceiling adjoins conditioned space.
5. Coastal Virginia so temps generally range from 20's to mid 90's.
6. I'd be fine with maintaining 65 in the cold months and 75 in the hot months.

I only ask because most generic calculators seem to think a 36000 BTU unit is more appropriately sized for that space, however a very detailed calculator that accounted for every detail like insulation, wall length, etc spit out estimated loads of 12000 BTU cooling and 21000 heating. The space is very well-insulated and the entire ceiling adjoining conditioned space obviously makes a huge difference so 24000 may be perfectly fine. Just looking for a sanity check. Thanks.

 

[justinjoyal]

Definitely not more than 24k. Less if you have backup heat.

 

[Jim greengo]

I'd want more than 1 head for that area for circulation.

 

[Black Oak]

That's a lot of cubic feet at 11.5' high . If you run with 1 air handler , I'd say you need to move the air . Maybe an Ambient Air Cleaner or a couple fans .

 

[Mesozoic]

I just had a Daikin system installed in my attached garage, fully insulated, 3 garage doors. I have 2 indoor coils, a 7000 BTU/hr in my 130 sqft office and a 24000 BTU/hr unit for the main floor, which is about 1700 sqft. The system is a 3-ton multizone. Ceiling height is 13.5’. The Manual J calc is detailed and conclusive, no doubt about that.