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Thread: Advice on how to cool and dehumidify my little work shop.

  1. #1
    Zaid19 is offline Plastic
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    Default Advice on how to cool and dehumidify my little work shop.

    I have a small shed that Iam in the process of converting into a workshop, its roughly 11'x15'. Iam almost done insulating it got all the walls, and currently doing the ceiling. Now the current dilemma Ive been thinking about is cooling and keeping the humidity out. I live in southern Florida so Iam no stranger to hot and humid weather lol. Iam leaning towards a window ac unit, probably around 6000 to 8000 BTU. And getting a Dehumidifier, the plan is to have the AC on when Iam using the place and turning it off when Iam not in the shop and running the Dehumidifier when Iam not in there. Also there isnt any windows just a hole where a window used to be where Ill be hopefully sticking the ac unit into. Is the way Ive described a good way to to do it? or are there any other ways. Iam looking to explore all my options before I got out and buy the AC and Dehumidifier. Thanks in advance.

  2. #2
    t.jones is offline Cast Iron
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    Sounds like the plan to me ! Make sure the building is as air tight as possible. ( Hermetically sealed ) ---Trevor

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    MichaelP is offline Titanium
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    After you try current dehumidifiers that last for 1-2 seasons, I'm sure you'll use your AC instead.

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    A ceiling fan (can be a residential offcast) is also a nice accessory to keep moisture from building up in a humid climate.

  5. #5
    oxford is offline Aluminum
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    I would personally just run the a/c and skip the de-humidifier. I don't think there will be much difference in the electric cost between the two.

  6. #6
    mach2 is online now Cast Iron
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    I use a 6000 BTU window air conditioner mounted in the wall for 500 square feet. There are times in mid summer here in Indiana when I wish the conditioner were bigger. The air conditioner runs continuous from June to September. I'd skip the dehumidifier too. Don't let the temperature and humidity fluctuate or you will have lots of condensation, pronounced rust. Also be sure your floor has a vapor barrier to help keep the humidity low to begin with.
    Last edited by mach2; 06-10-2013 at 06:11 PM.

  7. #7
    Zaid19 is offline Plastic
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    So from what you guys recommend its looking like that it will probably be more efficient and pretty much the same cost as if I were to just leave the AC running at all times. I never thought about adding a ceiling fan, does that keep air circulating while the AC is off to keep condensation from happening or at least keep it under control? As for the Vapor guard on the floor Ive totally forgotten about that part, definitely changes the budget a bit lol. Any recommendations for how to put in the vapor guard never done that before. Thanks for all the advice guys I appreciate it, alot of helpful ideas so far.

  8. #8
    MichaelP is offline Titanium
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    IMHO, the only meaningful vapor guard for your particular case is placed before the concrete floor is poured. But I'm not a builder and don't play one on TV. If you already have a slab, I'd leave it alone and won't cover or paint it with anything. You'll be glad you have a concrete floor when you have something like an oil spill (and you will get them regularly in your home machine shop). Bare concrete works like a giant sponge and stays non-slippery unlike epoxy covered floors, etc.

    Now about your AC. When you're away from the shop, just adjust the temperature up to make it easy for your wallet. You can think about installing a humidistat instead of thermostat if cooling is not your priority (which very well may be the case even in FL if the shack is well insulated). It won't be a problem to install it later when you have an idea of how much cooling you need, and what humidity drop you get at this cooling level. You may even cobble up a more sophisticated system which will use a thermostat when you work in the shop and then switch for humidistat control when you're out. Keeping relative humidity at or below 50% will help you protect your tools from rusting.

  9. #9
    Bill D is offline Titanium
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    a window ac unit is cheap but loud inside and out. I can not find any db ratings on them. you might consider a mini split ac for less noise and efficiency. For the amount you will run it the SEER rating is important a good split system can be almost 75% more efficient then a window unit.
    As far as vapor barrier best bet may be plastic then plywood or concrete on top.
    Bill D.

    PS: Friedrich brand was quietest I could find several years ago. About 5 DB quieter then next ones. that means about 50% quieter at low speed, similar reduction in outside noise. 10DB increase is double the noise.

  10. #10
    Zaid19 is offline Plastic
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    Yeah I just have a plain ol' poured in slab. Interesting Ill definitely be looking into the humidistat/thermostat idea. Iam also digging the Mini Split AC too, there kinda pricy though. So do all AC's have a SEER rating or just the Mini split systems and Iam assuming the higher the SEER the better in power savings? Thanks for advice.

  11. #11
    mach2 is online now Cast Iron
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    For under slab :

    High Performance Vapor Barriers | Raven EFD

    For existing slabs and many other conditions:

    Versatile Building Products, For The Best Deck & Garage Coatings, Epoxy Floor Coatings, Urethanes, Industrial Floor Coatings

    Any kind of central system is going to be more efficient and installed in a closet will be less of a noise problem. A window air conditioner has the initial cost advantage hands down.

  12. #12
    frank46 is offline Aluminum
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    I have a 3' circular 3 speed floor fan. Leave the back door open and with the rolling door open the garage cools down fairly fast. All bets are off when the temp/humidity index reaches 105 or better. Frank

  13. #13
    Bill D is offline Titanium
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    I believe all ac units have to have a SEER and/or COP rating on the label. The higher the number the more efficient. On a split ac system you really have to have a vacumn pump to install them or install and have a ac guy come out and vacumn it down. I think they are all 240 volts with a remote control so they can be mounted up high out of the way. Some units can be mounted flush into the ceiling/attic. I have to say I have no idea how there filters will do in a shop. maybe too much oil/smoke in the air or sawdust.
    Bill D.

    the links below first one is to show the ceiling evaporator I mean. No idea if that is a good brand or not.
    second link is the system I installed in my house. Indoor fan is four speed, has to be dead quiet to hear it run at lowest setting. Condenser is VFD Drive variable speed, very quiet at low speed outside

    Ceiling Cassette Systems – Fujitsu Ductless Mini-Splits

    Breeze


    some general info below

    Ductless Mini-Split Air Conditioners | Department of Energy

    Seasonal energy efficiency ratio - Wikipedia, the free encyclopedia

  14. #14
    James H Clark is offline Cast Iron
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    Zaid: I use a large window unit in my shop,(29000) BTU. I have about 900 square feet with 12 foot ceilings (building insulated). I also use a dehumidifier in the off season. I recommend mounting the AC unit up high in the wall, higher than a normal window. It's worth cutting a new window up high, because heat rises and cool air falls. This works well and eases the strain on the AC. I also keep a little box fan moving air around the shop. Good luck.

    JH

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    Zaid19 is offline Plastic
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    Yeah honestly noise really wont be an issue, Iam used to sleeping with my big old AC unit outside my window at night lol. Cutting a hole higher on the wall wont be a problem at all, so definitely be doing that. How much does the paint I can use on the floor usually run? Man this is going to be a tuff decision and so many ideas, unfortunately my budget is only so much, but then again the money Iam going to spend on a AC and a Dehumidifier, I can buy something that does both, lol I wish I was more experienced in these things. Again all awesome ideas thanks again.

  16. #16
    Bill D is offline Titanium
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    do not know if it really matters in your climate but some of the split ac units can be used as heat pumps for heating.
    How close are neighbors to hear the condensor 24/7?
    Bill D.

  17. #17
    Zaid19 is offline Plastic
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    Not very close, Iam on a 3 and a quarter acre lot, and my neighbor is probably about 100ft away from me. So your saying to run the heat to dehumidify? As for climate I live in southern florida, it gets cold sometimes lol.

  18. #18
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    metalmaster10 is offline Hot Rolled
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    I agree about just running the A/C at a slightly higher temp when not there instead of the dehumidifier! I have tried 3 different dehumidifiers and they were all the same. They didn't do a great job and added heat to the area, then you have to either plumb it into a drain or empty the tank a couple times a day. A slightly smaller A/C unit will dehumidify better than a big one. It Bly dehumidifies when the compressor is running and if is a smaller BTU the compressor will run longer each time, taking out humidity.

    As to the cost... A little 8 or 10,000 BTU unit will only cost a few dollars a month to run, but letting moisture build up on your precision tools will destroy thousands of dollars in expensive equipment... Trust me, been there... It sucks!

  19. #19
    Zaid19 is offline Plastic
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    So pretty much from what Ive gathered from everyone thats posted here, that Ill probably just end up using just a AC unit to cool and dehumidify, and probably install a humidistat. Its also looking like it will cost me the same monthly running the AC unit 24/7 as if I were to have a AC and a dehumidifier taking turns running on and off. At least thats what Ive been able to learn. Thanks for the advice guys.

  20. #20
    william33902 is offline Plastic
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    Quote Originally Posted by Zaid19 View Post
    So pretty much from what Ive gathered from everyone thats posted here, that Ill probably just end up using just a AC unit to cool and dehumidify, and probably install a humidistat. Its also looking like it will cost me the same monthly running the AC unit 24/7 as if I were to have a AC and a dehumidifier taking turns running on and off. At least thats what Ive been able to learn. Thanks for the advice guys.
    Thought I would contribute. I have a wood shop in south Florida and have went through the same questions.

    The problems with window units, they use water to cool the coils. So not only are they pulling humid air from the outside and bring it in, but it then sprays the coils with a mist of water. I've watched the humidity rise with a window AC turned on. The mini split is a great idea. You can get one online for the cheap and putting them in isn't that bad. The Hitachi is the Cadillac. And like someone already suggested, I also use a humidity switch to control the AC. I also have a dehumidifier running when I'm not in the shop. If the humidity gets too high, 50, the AC then turns on. So my bills aren't outrageous and I only cool the shop when I'm out there. I just turn the humidity setting to 30 and then the AC runs by temperature setting. Also, painting the floors helped a lot. I used a cheap oil based. Slippery, but everything beads up. I would have used a vapor barrier if I was planning ahead.

    My advice from my painful ($$$$) lessons:

    Mini split thats only on when in the shop
    Decent dehumidifier running all the time set at 45
    Honeywell switch that turns on the AC above 47 (Rainy days, or full dehumidifier)
    Paint the floor
    A nice weather door seal

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