Options to HVAC detached with partial attic truss?

[jpcjguy]

Hi all,

So my plan is a 48x30x12, doors on 48' eave side. See attached. Current design is with 18' of scissor truss for a lift bay and 30' of attic truss. The 30' side will be 10' walls with 2' raised heel on the truss. 9/12 pitch. 2x6 wall construction.
So if I want to heat/cool this building down the road, would it make sense to have 2 mini splits? Small one for the upstairs - area is 16x30 (480 sq ft.) and then a larger one downstairs. Or for the downstairs should I get 2 medium sized? on opposite ends of the garage to help with the scissor truss ceiling area not being the catch all for my heat in winter?

My house is 100% electric, so no gas or propane on the property, currently. Not opposed to having a propane tank behind the garage if that helps cut down on electrical consumption....
Any other reasonable options?

End result, I am trying to determine what future electrical loads I am looking at in order to ensure I size my panel appropriately. I am 200'+ from the house so the main wire is not something I want to upgrade later!
So once I have a plan for the HVAC, I can estimate what that future load would be and then add that to calculations for the rest of the garage.

Thanks!

 

[justinjoyal]

Before we can help you, we need the following:

- zip code or city/state
- insulation R-value for slab, walls, ceiling
- type of windows and doors and their size
- front door orientation
- what temperature do you want to maintain inside during cooling and heating seasons
- do you plan on opening the doors frequently or not
- what kind of work will be done in there

 

[jpcjguy]

Before we can help you, we need the following:

- zip code or city/state
- insulation R-value for slab, walls, ceiling
- type of windows and doors and their size
- front door orientation
- what temperature do you want to maintain inside during cooling and heating seasons
- do you plan on opening the doors frequently or not
- what kind of work will be done in there

23103 - Richmond, VA
No insulation under 4-5" slab. planning on rockwool - R23 in the walls,R-38 in the ceiling.

1 man door and 2 overhead doors that are 10' wide and 9' tall, no windows
Doors all face the west (very slight north)

Plan is for automotive work, ATV work/storage, looking at putting my free weight gym area in the corner.

As for temperature, in the winter mid-50s and summer 80ish? not looking to maintain it at a perfect 70 degrees. I am ok with moving the thermostat some and hour or two before I go in there.

Hopefully that is enough information- if not ask away. Thanks!

 

[justinjoyal]

This is the quick load calc I did with the data you provided.

Design indoor cooling temp 78, indoor heating temp 55.

Do you plan on heating only with the heat pump(s) ?

 

[bobbyjean]

i think ductless is the way to go on your build...maybe go with a two head unit like this/ Fujitsu / F2L18W07120000

 

[jpcjguy]

This is the quick load calc I did with the data you provided.

Design indoor cooling temp 78, indoor heating temp 55.

Do you plan on heating only with the heat pump(s) ?

justinjoyal - thanks for this info! so to ensure I am interpreting it correctly I need about 14K BTU to cool and 23K BTU to heat it? This is assuming a flat ceiling at 12ft? So I could equal out the scissor truss area that is higher to the 10 ft ceilings on 30ft?

 

[jpcjguy]

i think ductless is the way to go on your build...maybe go with a two head unit like this/ Fujitsu / F2L18W07120000

I like the idea of a 2 head unit - one sized of for the attic room and the other for the bottom.

 

[justinjoyal]

justinjoyal - thanks for this info! so to ensure I am interpreting it correctly I need about 14K BTU to cool and 23K BTU to heat it? This is assuming a flat ceiling at 12ft? So I could equal out the scissor truss area that is higher to the 10 ft ceilings on 30ft?

Yeah that’s pretty much it.

However I just realized I missed the 2nd story attic space... should not make a huge difference though.