Sizing a mini should lit with heat pump for a garage???

[Pziddy29]

Hey guys so I am looking for some advice on sizing a mini split with a heat pump for my garage.I live in NJ.So far I've seen some different numbers.The garage is a 19x25 with 13 foot ceiling.Has new fiberglass insulation and new drywall.Ive seen estimates between 9000btus all the way up to 24000btus.I am looking at GREE units.I just don't know what size to chose.Any advice is greatly appreciated.I normally prefer to have the indoor temp be 70 degrees with a max of 72 if that matters.


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[Firebrick43]

2x4 or 2x6 walls? R value in ceiling? Also you state only a tolerance for a max of 72. If you bring in a heat soaked car on a hot day even a 24k unit could have a hard time getting below 72 for at least an hour or two. On the other hand the bigger the unit the less efficientcy and it won't do as well taking humidity out.

 

[Pziddy29]

2x4 walls,not sure of r value on ceiling but it's framed out in 2x8.Moslty 1/2 drywall fire guard and one wall has 5/8 drywall also fire guard.

 

[Firebrick43]

i am really sorry but we are still throwing darts blindfolded. In the grand scheme of things the drywall is a small part of a buildings thermal performance. Ceiling insulation is number one, wall construction and window /door construction is number two. Also site orientation and roof /wall color matters. For example, a west facing uninsulated garage door with no shading can be unbearably hot on a summer afternoon. If your close to the ocean a poorly sealed and uninsulated door facing north east can be bone chilling cold during winter storms.

Also what gree unit are you looking at? They have at least two lines maybe 3. The terra has much better performance at low temps

 

[Pziddy29]

Sorry I have R30 in the ceiling.Asphlat roofing tiles.My garage door faces north.Door is solid wood uninsulated with single pane windows.I have 2 other windows that are also single pane and 2 doors that are single pane glass.

Gree model number RIO24HP230V1AO
And
RIO24HP230V1AH

Both are 24k btu units


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[yeldogt]

You have about 500sf. A well insulated/ tight building (spray foam) can be conditioned with 1 ton per 1000sf (or more). It drops from that point -- even at 1/2 that you are 2x with 2 tons (24btus). High ceilings you only worry about A/C under 8'.

I heat my 1700sf studio with about 33k of heat -- and that's oversized to bring it up quicker.

It all about leakage and how you are going to use the building ... need for recovery.