Barn A/C or Not?

[Lindy911]

I recently built a 26x36x10 pole barn with wood siding and OSB underneath. No insulation or ceiling either. Roof pitch is 6/12. My part of Texas is hot and humid, so a mini split A/C would be great. So, I thought about adding a 36000 btu unit, but I wonder about its effectiveness. Spending the money for foam insulation is rather pricey, and with no ceiling, I wonder about effectiveness. Thanks in advance for your comments.

 

[The Cobbler]

without insulation your heat gain is huge, especially at the roof with the sun beating on it.
I suspect it wouldn't be very effective

 

[strutaeng]

The spray foam will be effective without the ceiling. Thermal barrier will be at the roof deck instead of the ceiling, provided they add a sufficient amount of foam. What does the building code require there, R30? That's like 5" of foam.

Is the roof wood trusses?

If you can live with a ceiling and do blown in cellulose, that the least expensive option, on a cost per R value ratio.

With decent ceiling insulation, just a 2 ton conventional split system will probably work. If you can live with a bit of ductwork below the ceiling, even better, but probably wouldn't need much ductwork anyway. Way cheaper than 3 ton mini split. You should have plenty of options in Houston area.

Personally, I think mini splits are uneconomical above 3 tons. You can get (3), 12,000 btu for cheaper than 3 ton single unit.

You also have to consider use. Is this going on 24/7? It may take 30 years to recoup mini split cost for a building that's used occasionally. Do a cost/benefit analysis.

Lastly, window AC units are an option. They are very economical and easy to install, just a ceiling fan. A 2 ton window ac is probably around $1k. $0 installation cost if you DIY.

I hope this helps.

 

[bluegoose972]

I'm up just north of Austin, TX and looks like we are in similar spots. I have a guy that quoted me $1/bf for closed cell and recommended 1" on walls and 2" on ceiling with an attic/exhaust fan to pull out the trapped hot hair. Also went with a white roof to give myself every advantage to keep the temps under control.

Just afraid that the doors will be my limiting factor. 2 ea 10'x10' doors will definitely present some cooling challenges.

 

[HoosierBuddy]

I wouldn't attempt it.

Technically it would be difficult as the A/C would have to be way oversized to deal with the heat load of an uninsulated structure, meaning a heavier outlay of cash to buy the system and possible additional expenses if you don't have the amps available to run the oversized system in your barn already (might have to upgrade electric service).

Economically it would be difficult as you power bills would absolutely eat you alive. You'd either be forced to go turn off the system you just paid for, severely limit the number of minutes you run it, or go back and insulate after the fact (after you already paid for oversized equipment to NOT insulate from the beginning.)

For me...I'd have a moral issue with using that much power when I could easily avoid it. I'm concerned enough about the environment that I HOPE I would not use that many kilowatts on something so easily remedied with good insulation OR avoided my just not installing a/c in my pole barn. People having been living in Texas for thousands of years with out air-conditioned pole barns, right?

Off my high-horse. Seriously...do whatever you feel is right for you.

Phil

 

[Sevenhills1952]

The original old section of my house is uninsulated. When I first bought it 40 years ago I installed a turbine that summer. Cutting opening I remember that blast of hot air, and turbine really helps.
Pole barns have cupolas and vents. Large trees around. Everyone thinks it has central air but they don't.

Sent from my SM-S320VL using Tapatalk

 

[dcg9381]

I have a 60x40 steel shop building in central Texas. My walls are 16' high. I have a highly reflective galvalume roof.

Building has 3 14'x14' R5 doors and a 4' person door. I can tell you that the big doors **** as far as insulation. I've weather stripped them, but they still have all sorts of holes for air.

For about $5k (off the top of my head) 3-4" of open cell foam insulation, which turns out to be around R13 or so. No vents.

This is my first year having full power and AC:

I'm running 2 x 24K Ductless split units (4 tons total) - cost for both those units was around $2300 with me doing the install.

I have been able to cool that shop off to the 70s with it in the high 90s ambient, so far...

I never tried to cool it without insulation. I balanced the cost of the R13 insulation against the fact that I only run HVAC very part time. Economics are different if you're going to "live" there. If I was using it all the time, I'd probably insulate to R25, buy better doors, and get more efficient HVAC systems.

@HoosierBuddy (Phil) has a moral issue with using all the power. I can tell you that my circuit breakers on those units are 15A, so they're pulling (for sure) under 12A each. To help with issues of fossil fuel / carbon morality, I stuck 6000 watts of solar on the roof. I just got an electricity bill of $24. $22 for having a power connection to the grid and $2 net use of electricity for May. Did I mention a 40A hot tub?

 

[HoosierBuddy]

@HoosierBuddy (Phil) has a moral issue with using all the power. I can tell you that my circuit breakers on those units are 15A, so they're pulling (for sure) under 12A each. To help with issues of fossil fuel / carbon morality, I stuck 6000 watts of solar on the roof. I just got an electricity bill of $24. $22 for having a power connection to the grid and $2 net use of electricity for May. Did I mention a 40A hot tub?

Sounds like you went about it the right way.

I just note that in the U.S. we use energy at a multiple of anywhere else in the world. I'm part of that. I have a hot tub and a heated/cooled garage as well. I do try to be intentional about my energy usage though and I'm consistent in the message I give out to other people, which is don't just waste it. Cooling an uninsulated garage would be just wasting power. I was harping to my 83 year old mother about the 3rd refrigerator she has plugged in her garage yesterday that has 1 12-pack of diet coke in it and a freezer full of something (possibly alien) that looks like it was chipped out of a melting glacier near an arctic research station. Use what what you want if you can afford it. Just don't waste it.

Phil

 

[dcg9381]

Phil, I'm sorta poking fun. Your energy concerns are legitimate and obviously I feel the same way as well (hence the solar install).

> Cooling an uninsulated garage would be just wasting power.

I'm generally agree. We can look and figure out the ideal insulation level for our climate(s), but I'm pretty sure those insulation levels are calculated at full-time use.

Most of us can't afford to build "500-year" class homes or even insulate our shops R30 insulation, so there is an economics of use here. At one extreme, it might be better to use the standard steel building "drape over" insulation at R5 and over-power the AC system if it's a shop that you're going to cool down once a month. Is that wasting power? Perhaps, but I'm not sure that the eco-impact of spraying it with R30 worth of foam in that use case is necessarily the right answer.

If my mom had 3 fridges running, I'd have the the same opinion about a 2nd or 3rd fridge too...

 

[Lindy911]

Thanks to all for sharing your thought and experiences. I’m going to think about insulation and adding some sort of ceiling before adding A/C