3 Car Detached - Full Envelope Foam Insulation - Mini Split Question

[Stroonzo]

I am in the process of finishing out my detached, 3 car, 20 x 30 unfinished garage. As it currently stands, the entire garage is unfinished (no insulation, no sheetrock, etc). The 8' ceiling of the garage consists of 2x10 joists 12" O.C. that is for the most part completely decked above with plywood.

My plan for insulation is a full envelope foam job (that is to spray the walls, the underside of the roof, and not the ceiling joists).

My concern has to do with my mini split AC. I want to make sure I have air flow and conditioned air in the attic storage space. I am not looking for it to be 78 degrees up there, but I would like to keep the temp and moisture manageable.

Having the mini split in the bottom half of the shop that is fully sheetrocked (walls and ceiling) is not going to allow air to circulate above.

In the summer heat, thermodynamics is not going to play nice in the space above either.

I am wondering if anyone has dealt with this issue. I am considering / questioning passive or active attic ventilation through the ceiling into the attic, or even the thought of a dual zone mini split.

Your thoughts?

 

[dmoore]

Given that you essentially have "two" rooms, I think what would be a great solution here is a split-mini, dual-zone unit. This way you could have the temp/humidity in the upper attic at one level and then another temp/humidity at the garage level. Given that you'll have a lot of air exchange on the bottom, compared to the top attic in a full envelope, it would seem like a logical solution.

http://www.thermospace.com/ductless_split/dual-zone_inverter_mini_splits.php

 

[mo2872]

Dual zone mini, +1 from here.

Wish I'd gone spray foam on my build. If for no other reason than to test/compare it with the house which is traditional batts/blown.

 

[theoldwizard1]

Dual zone. 2 thermostats.

Open your wallet wide when you get your quotes for spray foam !

 

[Gerald O]

I'm going with a dual zone mini for my own 32 x 24 project with attic. Just received my equipment today. I had the shell built last summer, now it's up to me to finish the inside.
http://garagejournal.com/forum/showthread.php?t=200759

My attic room will be closed off from the garage space below with a door at the top of the stairs. Since I may keep the two levels at different temperatures I will be insulating the garage ceiling/attic floor also.

I'll be insulating with conventional fiberglass batts, but our climate is relatively mild here. R15 in walls and R30 in the ceiling.

 

[Stroonzo]

Well, it sounds like the dual zone mini split is the answer. I guess for a couple of hundred more on the AC, it will end up being the most effective solution rather than trying some forced air circulation contraption. Thanks!

 

[JakeKohl]

If you are using those to heat as well, make sure you research the lowest settings that the units will work on. Mine won't adjust to a thermostat setting lower than 60 degrees - I found that a little disappointing for the garage environment because I would like it to be about 45 or so when I'm not using the space.

 

[mo2872]

If you are using those to heat as well, make sure you research the lowest settings that the units will work on. Mine won't adjust to a thermostat setting lower than 60 degrees - I found that a little disappointing for the garage environment because I would like it to be about 45 or so when I'm not using the space.

Set the timer for it to only be on at times you're most apt to be in there. Mine is set to turn on at 4 PM, off at 1 AM(night owl, I'm out there late).