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Discussion Starter #1 (Edited)
So construction will start soon on my detached garage. I'm looking down the road to heating and cooling the garage. Basic layout shown below with shop area of 30' X 36' with two small rooms on the back, one 10' X 10' and one 10' X 20'.

I will want the shop area comfortable to work in (@ 70 degrees) year round and I'm hoping to do this with a mini split. The other two rooms would be fine if they were cooler or warmer than that as long as they were not really hot or cold and the humidity was under control.

Would air exchange from the shop area using crawl space fans be enough to keep the humidity down and temperature decent in the two small rooms?

Garage will be all block construction with 2" foam board insulation on the inside of the exterior walls, with walls framed over the foam board and fiberglass batts in the framed walls. Ceiling will also be insulated. The wall separating the shop space from the two small rooms will not be insulated.

No windows will be in the garage. Only one insulated garage door, one walkout door, and the two doors to the smaller rooms.

Shop area will have a 12ft ceiling. Two smaller rooms will have 8' ceilings so the smaller rooms would be 800 cubic feet and 1,600 cubic feet. Using four 200 CFM crawl space fans, two in each room, one pulling air in and one pulling air out as indicated by the blue arrows, the air should be completely exchanged in the small room every 4 and 8 minutes. Is that correct?


Any thoughts, opinions, or other options would be appreciated.


 

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Use a multihead minisplit.
You’ll make things unnecessarily complicated-and noisy- with all those fans buzzing.
What will the rooms be used for?
 

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My 2 cents: Install a mini split with two heads , one mounted where you show in the pic and the other mounted on the same wall of the 10x20 room . Then you can do your fans in between the 10x20 room and the 10x10 room . I am no expert but that is a lot of space to condition with a single head mini split .

I have a 24x26 man cave garage with 12 ' ceilings and condition it with a 24K mini split but it is one large open space . I hope others chime in I am interested to see if others think your original plan will work .
 

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You will still need to size the mini to condition the entire 30x46 building doing the fans the way you want.


Putting the mini where you show, will cause a warm spot at least toward the over head door. It better to have the head blow with the long wall.
 

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Discussion Starter #5
Use a multihead minisplit.
You’ll make things unnecessarily complicated-and noisy- with all those fans buzzing.
What will the rooms be used for?

That's definitely an option. Was just looking for possible ways to save the additional cost if it were possible to do so.



Rooms will be for storage.
 

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Discussion Starter #6
My 2 cents: Install a mini split with two heads , one mounted where you show in the pic and the other mounted on the same wall of the 10x20 room . Then you can do your fans in between the 10x20 room and the 10x10 room . I am no expert but that is a lot of space to condition with a single head mini split .

I have a 24x26 man cave garage with 12 ' ceilings and condition it with a 24K mini split but it is one large open space . I hope others chime in I am interested to see if others think your original plan will work .

Yea, I figure two heads is probably what I'll end up with. Just curious if one might work. How does that 24K do in your 24X26? How are you insulated?
 

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Discussion Starter #7
You will still need to size the mini to condition the entire 30x46 building doing the fans the way you want.


Putting the mini where you show, will cause a warm spot at least toward the over head door. It better to have the head blow with the long wall.

Yea, I assume there are better and worse places to mount them. I just threw it on there in a random spot. A two head mini split seems like a better option, but I'm still reading around and checking opinions. I'll get my local heat and air place out to check it out when the time comes too. I figure it'll be another year before I heat and cool it. I want to see how hot and cold it actually gets before I make the jump. I will have a dehumidifier running from day one.
 

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That's definitely an option. Was just looking for possible ways to save the additional cost if it were possible to do so.



Rooms will be for storage.
Make sure to check local code, to see what’s required for small rooms off of a vehicle storage area.
May not be possible to share airflow between the garage, as carbon monoxide could enter those rooms and become trapped.
 

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Yea, I figure two heads is probably what I'll end up with. Just curious if one might work. How does that 24K do in your 24X26? How are you insulated?
Sorry for the late reply , been busy :biggrin2: . The mini split in my man cave garage does an excellent job of heating and cooling . My exterior walls are 2x6 with 1/2 " plywood on the outside and the inside no sheetrock . Exterior has house wrap and vertical metal siding . Insulation is kraft faced R19 conventional fiberglass . The ceiling is also metal siding with the same kraft faced R19 . At some point in time I will probably add another layer of unfaced insulation in the " attic " but the electric bills are so reasonable I am in no hurry .

I have four small vinyl insulated windows , an entry door with a storm door and two insulated garage doors . I have aluminum radiant barrier stapled to the bottom of the roof rafters creating a 3 1/2 " air space between it and the roof deck . Full length ventilated soffits and ridge vent . That's it in a nut shell .
 
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