AC for shop/shed

[paulsharvey]

We don't have a 'shop' topic? Anyway, I have a 24x28x7 pole barn shed/shop/dog house, that gets crazy hot. In the past, I've used cheap, old, used, window units ranging from 8000 btu to 5000 btu, and they've taken the edge off. 3.5 of 4 walls are roofing metal, with some 1/2" Styrofoam insulation boards. I'm fine with 85 and low humidity, 80 would be better, but it's a Very dusty environment. Between grinding dust, sawdust, dog hair, ect, the window units have lasted 1 or maybe 2 years. This is not meant to be cool; and doesn't need to heat, but it does need to be Cheap, and preferably something dust/grit resistant. Not doing MrCool type set up. What are yall using?

Current cut out is 15"×19", but can be modified easily.

Floor is broomed concrete, not dirt.

 

[paulsharvey]

Wife is more concerned with the dogs than me being comfortable working in there...

 

[MoKelly]

Wife is more concerned with the dogs than me being comfortable working in there...

Ha. My wife has a sign on her desk that says:

“Missing - husband, shotgun and dog.

Reward for dog”.

 

[ponytug]

(More) Insulation?
With more insulation, the units won't work as hard, or as long, and should last longer.

All the best,

Peter

 

[FPGT72]

The issue might be because the small size of the window AC you have been using. It likely runs the entire time.

In my shop I have a 240v 25000BTU "window" ac, and it has been in there for at least 15 years now, and (knock on wood) is still going strong. It will cycle on and off if I am out there long enough. My building is roughly your size but much taller.

I have a loft now, and it is really warm up there in the summer, I am going to do two things to help solve that issue, first is gable fans to pull that hot air out, the second is a smaller mini split. One reason I am going with the mini split is the heavy part is going to be down low, up high all I need is one hole.

 

[2manyrocks]

Basic BTU calculator: BTU Calculator

5-8,000 window units can barely cool a small insulated bedroom. With a larger, poorly insulated shop in sunny Florida, you'd probably need 25,000 btu if not 3 ton.

One advantage of mini splits is you only need about a 3" hole in the wall to run the linesets and power. Disadvantage is you must be meticulous about flaring and tightening the lineset connections to the correct torque to keep them from leaking, and you can't kink the tubing. Mini split can also provide heat.

 

[paulsharvey]

Basic BTU calculator: BTU Calculator

5-8,000 window units can barely cool a small insulated bedroom. With a larger, poorly insulated shop in sunny Florida, you'd probably need 25,000 btu if not 3 ton.

One advantage of mini splits is you only need about a 3" hole in the wall to run the linesets and power. Disadvantage is you must be meticulous about flaring and tightening the lineset connections to the correct torque to keep them from leaking, and you can't kink the tubing. Mini split can also provide heat.

So, let say I improve the insulation; we aren't trying to get to "room temperature"; just not dangerous; and workable (80-85, and get some/most of the humidity out). Is it better to run a smaller system constantly (well, in theory maybe 16-18 hr/day)?

So; the 5000 and 8000 btu cooled satisfactory; but they didn't last. Now; they both were over 10-15 years old, and taken out of a house the owner upgraded to mini-splits; but at the same time; I don't really want to buy a new $150-200 window unit every year. So, I guess the question really is; is there a better way to keep them alive in harsh environments, with extremely hot shed, undersized unit, with tons of dust/dirt/dog hair.

 

[paulsharvey]

So, back story; this started as a 12x16 3 walled, dirt floor, pole barn, that I build for approx $200. Since then, it's been expanded, concrete floor poured, ect. When I first enclosed the bigger footprint; it was fine 3 season; but summer; completely unusable. My first thoughts where swamp cooler or dehumidifier. The swamp cooler the issue is, you basically have 80-85 degree air, But 100% humidity. The dehumidifiers I've worked with at an old job, did keep humidity down, But they actually made a utility room hotter.

Hindsight being better, I might have done block walls; metal roof, with planned out insulation, like an R7 on the roof; but the way its built, it's hard to get a good air seal/decent insulation. I've bounced the idea around of using Kraken Spray foam; and even if I only get 1/2" of foam (R-3.5); I would improve the air seal.

 

[Runner]

My shop space is a 32 x 30 Perka building, which has 2 x 6 girts in the walls and ceiling with 6 inch (I think R-19?) batt insulation. I have a thru-wall AC/heat unit like this https://www.lowes.com/pd/Koldfront-...tioner-Heater-Included-with-Remote/5013393371 except I think it's about 13000 BTU. It is typically mid- 90's around here in summer and it will keep the temp at 80 on hottest days, usually cooler.

It helps to be strategic. If I know I will be working in there, I turn it on in the morning so it can maintain the lower night time temp and not try to cool it down from 85 or whatever by waiting to turn it on in the middle of the day.

My unit is older, completely manual, no thermostat or timer, etc., but when it dies, I will be buying a new one similar to the one posted above (only with as many BTU heat/cool as I can get) and with the timer and thermostat, assuming our government still allows them to be sold. Anyway, this has worked for me for a number of years with no problems and I would definitely do it again given the same circumstances.

P.S. The insulation made all the difference. I checked the temp. of the inside of the steel siding one day before installing the insulation and it was 130 degrees. The building was like an oven prior to insulation. I know this is obvious to anyone with two brain cells, but I was still surprised at how much difference even such a minor amount of insulation could make.

 

[JJT]

I'm not in Florida and my shop is well insulated.

"What am I using?" I have a single 10K btu window ac unit that I turn on if I'm spending any amount of time in the shop when it's hot out. It does an adequate job of cooling the bay I'm working in. No way could it cool the entire 1200 sq ft building. At my age I'm happy with a little cool/dry air moving around me while I work.

 

[EddieWalker]

My garage has a metal roof without a ceiling or any type of insulation. My Mom's house has R13 fiberglass insulation in the walls and 2 feet of blown in insulation in her attic.

In Summer, it's hard to just breath in my garage, the heat is so oppressive. You are better off standing outside in the sun then you are inside my garage. I would guess it's ten degrees hotter inside my garage compared to the outside temperature.

My Mom's garage is pleasant. No AC, or anything to keep it cool, just the insulation. I've never checked the temperature in there, but I would guess it's at least 10 degrees cooler inside her garage then outside, and I wouldn't be surprised if it was even cooler.

My long term goal is to insulate my garage by putting metal R panels on the ceiling. My trusses are every 4 feet, so metal roofing will be perfect. Then blow in 2 feet of insulation.

 

[ruffdog]

Being that the main issue is "tons of dust/dirt/dog hair", maybe a large volume fan to move air THROUGH the building?

Sidewall Propeller Exhaust Fan, Product # SBE-2L30-7X-QD-DR3, 7992-10921 CFM | Greenheck

 

[bigtiller]

If you can get the ceiling insulated to some where close to an R50, it will probably cool it enough that you won't need anything else.

My sheds ceiling and walls are well insulated and I have an undersized de-humidifier running. I go in there to get cooled off before I go in the house for supper.

I go to the shed about 3pm every day of the year to check the temp and empty the de-humidifier in the warm months. At that time, it has never been above 81° or below 33°

 

[paulsharvey]

If you can get the ceiling insulated to some where close to an R50, it will probably cool it enough that you won't need anything else.

My sheds ceiling and walls are well insulated and I have an undersized de-humidifier running. I go in there to get cooled off before I go in the house for supper.

I go to the shed about 3pm every day of the year to check the temp and empty the de-humidifier in the warm months. At that time, it has never been above 81° or below 33°

Yeah, R-50 is never gonna happen; if I could get it a consistent R-5, with no air leaks, that would be awesome. It's frankly harder to retro fit a pole barn into conditioned space than it is to build it with that intent from the ground up.

 

[paulsharvey]

Even when I worked on PEMB (red iron buildings; pre-engineeered metal buildings), with the roll insulation between the frame and skin; we would chase light holes in corners, and dang birds getting in, forever. I dont think we ever did one conditioned without a drop cieling...

 

[paulsharvey]

I just went ahead and picked up the cheapest window unit ac in stock; a 5000 btu Toshiba, and some additional 3/4" foil and Styrofoam board; as well as ordering a 2 can pack, gun, and cleaner of Kraken spray foam. It wasn't cheap, and 2 cans is going to do only like 40 sq ft; but I couldn't make my self just make the leap to order a 6 or 12 can kit. Gonna do some of the odd shaped areas of the cieling with that; where I have nothing to attach foam board too.

That foam; I see it widely used in E. Europe on videos; but only a handful of videos in US of people using it; with mixed reviews.

Hindsight being maybe not 20/20; but closer; I really wish I would have started from the ground up with an intent to insulate this structure. But when it was first built; it was just a place to keep the rain off a mower.

 

[MossRoad]

Could you use thinner lumber and make a lattice frame in the high areas to attach the foam board to instead of using expensive spray foam?

 

[KennyG]

Since you are concerned with humidity, I would focus on air intrusion first - sealing doors and windows, vapor barrier, etc. You don't want to oversize the A/C unit. I had a house with an oversized central air unit. It only had to run about 20 or 30% of the time to keep the temperature down so it wouldn't control the humidity. Kept the house cool and clammy.

 

[paulsharvey]

Since you are concerned with humidity, I would focus on air intrusion first - sealing doors and windows, vapor barrier, etc. You don't want to oversize the A/C unit. I had a house with an oversized central air unit. It only had to run about 20 or 30% of the time to keep the temperature down so it wouldn't control the humidity. Kept the house cool and clammy.

No worries about oversized unit

Sealing air intrusions is a never ending battle in a pole structure, and that's part of what I'm working on.