I'm having a 30x60 garage built that will be spray foamed and drywalled. I'm wondering if I go mini split 4 zones (wall mounted or cartridge) or central air. If mini spilt thinking of ducted and run metal tube down the middle with vents every few feet. Ductless, wall mounted 2 every 20 ft? I'm in Texas, DFW area, and looking for what will be more efficient and cheaper on electric bill. Interior will look something like the picture. It's just a rendering but it's close. There will be an office up top.
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HVAC recommendations 1800 sq ft garage
- Thread starter dieseldog
- Start date
Dedicate a zone or head to the office....the main area can probably make it with 2 heads depending on how cool you need to keep it. Run some basic Manual J heat calculator online and see what they're saying. You can also always do the rough in electrical work for a future location so the wiring is there if you decide you need it down the road.
Circulation will be a big need though with ductless units so I think you're going to want a couple of Big *** style large diameter fans for airflow. The generics are really pretty cheap and seem to work well.
Circulation will be a big need though with ductless units so I think you're going to want a couple of Big *** style large diameter fans for airflow. The generics are really pretty cheap and seem to work well.
aggie113
Well-known member
Very small unit for the office (maybe even window unit), and then two units for the garage. How much foam? Closed or open cell? How many/what size garage doors? Working in the garage or just parking/storage? Eyeballing it off that rendering, the cubic volume would be good with two 2 ton units. That would allow for temperature maintenance and times when rapid cooling/heating is needed after opening up the doors.
1 inch closed cell, 2 garage doors 10x10, working in the garage. Two 2 ton units sound more ideal.Very small unit for the office (maybe even window unit), and then two units for the garage. How much foam? Closed or open cell? How many/what size garage doors? Working in the garage or just parking/storage? Eyeballing it off that rendering, the cubic volume would be good with two 2 ton units. That would allow for temperature maintenance and times when rapid cooling/heating is needed after opening up the doors.
That’s better than nothing, but it’s not nearly what you should have.1 inch closed cell, 2 garage doors 10x10, working in the garage. Two 2 ton units sound more ideal.
mike93lx
ALLIANCE MEMBER
1", really? You need at least 1.5" for a vapor barrier, plus that's only about R6.
aggie113
Well-known member
Yeah, 2" would be better. I wish my 2" was 4" (at least on the roof).
racecougar
Well-known member
A) 4 separate ducted heads for a 30'x60' garage is beyond overkill, IMO. I run a single 24k unit in my 30'x60' and it does fine. Temp gradient within the building is less than 2°F. I agree with running a separate head for your closed off office, but improve on your insulation plan and you won't need so many heads. Which leads us to...
B) 1" of closed cell foam is beyond underkill. Bare minimum, IMO, is R-13 for your walls and R-38 for the ceiling, but the more you improve upon that, the more efficient and comfortable your building will be. You mention you want the building to be "efficient and cheaper on electric bill"; insulation and air sealing is the path to this.
Hopefully the 10'x10' doors are insulated sectionals and not roll-ups.
B) 1" of closed cell foam is beyond underkill. Bare minimum, IMO, is R-13 for your walls and R-38 for the ceiling, but the more you improve upon that, the more efficient and comfortable your building will be. You mention you want the building to be "efficient and cheaper on electric bill"; insulation and air sealing is the path to this.
Hopefully the 10'x10' doors are insulated sectionals and not roll-ups.
finn
Well-known member
How tall are your ceilings?A) 4 separate ducted heads for a 30'x60' garage is beyond overkill, IMO. I run a single 24k unit in my 30'x60' and it does fine. Temp gradient within the building is less than 2°F. I agree with running a separate head for your closed off office, but improve on your insulation plan and you won't need so many heads. Which leads us to...
B) 1" of closed cell foam is beyond underkill. Bare minimum, IMO, is R-13 for your walls and R-38 for the ceiling, but the more you improve upon that, the more efficient and comfortable your building will be. You mention you want the building to be "efficient and cheaper on electric bill"; insulation and air sealing is the path to this.
Hopefully the 10'x10' doors are insulated sectionals and not roll-ups.
Your experience makes me wonder if I’m oversizing, as my HVAC dealer and I selected a 3 ton for my 32’x75’ shop (2400 sq ft) and an 8’ tall ~10’ x~8’ utility / boiler / compressor room with no door.
The 8’x16’ - 8 ‘high office / bathroom area will have its own 6000 btu head.
I wonder if a single 24000 btu head would have been adequate for 2400 sf, even with the 16’ ceilings.
Our summer temperatures are moderate compared to much of the country, but on occasion it can get fairly humid, although nothing like Florida, the gulf coast, or the Carolinas.
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racecougar
Well-known member
12'7"However tall are your ceilings?
A) it would be 4 ductless wall or ceiling units. I have one in my 16x24 shed and it is not enough for Texas heat.A) 4 separate ducted heads for a 30'x60' garage is beyond overkill, IMO. I run a single 24k unit in my 30'x60' and it does fine. Temp gradient within the building is less than 2°F. I agree with running a separate head for your closed off office, but improve on your insulation plan and you won't need so many heads. Which leads us to...
B) 1" of closed cell foam is beyond underkill. Bare minimum, IMO, is R-13 for your walls and R-38 for the ceiling, but the more you improve upon that, the more efficient and comfortable your building will be. You mention you want the building to be "efficient and cheaper on electric bill"; insulation and air sealing is the path to this.
Hopefully the 10'x10' doors are insulated sectionals and not roll-ups.
B) I agree with you and will upgrade it to 2"
C) they are insulated.
I believe 20 ft.12'7"
Ceiling will be about 20 ft. AI told me for 1800 sq ft I would need 3-4 ton unit.How tall are your ceilings?
Your experience makes me wonder if I’m oversizing, as my HVAC dealer and I selected a 3 ton for my 32’x75’ shop (2400 sq ft) and an 8’ tall ~10’ x~8’ utility / boiler / compressor room with no door.
The 8’x16’ - 8 ‘high office / bathroom area will have its own 6000 btu head.
I wonder if a single 24000 btu head would have been adequate for 2400 sf, even with the 16’ ceilings.
Our summer temperatures are moderate compared to much of the country, but on occasion it can get fairly humid, although nothing like Florida, the gulf coast, or the Carolinas.
mike93lx
ALLIANCE MEMBER
At least 2". Consider that the bare minimunA) it would be 4 ductless wall or ceiling units. I have one in my 16x24 shed and it is not enough for Texas heat.
B) I agree with you and will upgrade it to 2"
C) they are insulated.
racecougar
Well-known member
A) it would be 4 ductless wall or ceiling units. I have one in my 16x24 shed and it is not enough for Texas heat.
Okay. This part was confusing.
If mini spilt thinking of ducted and run metal tube down the middle with vents every few feet.
Again, I'd advise way more than that, particularly at the ceiling.B) I agree with you and will upgrade it to 2"
What does your attic venting consist of?
Overboost44
Well-known member
Interesting replies. Makes me think I am being oversold for my well insulated 1000 sq ft garage with 24k having 14' ceilings, and then 12k in my 16' x13' upstairs.
bob smith1
Well-known member
- Joined
- Jul 2, 2026
- Messages
- 80
Details are being overlooked. Building size alone does not size the equipment. Only YOU can answer the dozens of others like temp set expectation, building air tightness, E value for building. Steel roof or? 1" is it for the ceiling? think again. ALL OH doors are major leakers and not efficient. Windows? Walk doors? In all, you need a load assessment.
Then there is the 'response factor', which means if those doors will open a lot, and you want that temp returned quickly, your 4T could be close, but I still believe if you need that, you need to fix your building.
And why do all DIY shop guys hug minis like they are so awesome? They literally wrote the book on reefer leaks, and no one will fix it once you screw it up. I don't hate them, but you DO get to jack with reefer lines.
My solution? A residential packaged unit. If not familiar, look it up. Just off the cuff, 2.5T is prob about right for your space with reasonable expectation. If you want office conditions 3T.
Ducting is ALWAYS going to give you more comfort, and how the ducting gets done and tuned matters! Sizing and such, you size office space with dampers. However, it's very common to separate office from shop due to fumes and return air. That's how I fly.
Then there is the 'response factor', which means if those doors will open a lot, and you want that temp returned quickly, your 4T could be close, but I still believe if you need that, you need to fix your building.
And why do all DIY shop guys hug minis like they are so awesome? They literally wrote the book on reefer leaks, and no one will fix it once you screw it up. I don't hate them, but you DO get to jack with reefer lines.
My solution? A residential packaged unit. If not familiar, look it up. Just off the cuff, 2.5T is prob about right for your space with reasonable expectation. If you want office conditions 3T.
Ducting is ALWAYS going to give you more comfort, and how the ducting gets done and tuned matters! Sizing and such, you size office space with dampers. However, it's very common to separate office from shop due to fumes and return air. That's how I fly.