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  1. #1
    Join Date
    Jul 2019
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    3
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    Shop - 30' x 60' x 12' -- Considering adding A/C

    I am located in Oklahoma.

    I have a metal fabrication business that I run with just my son and myself.

    We have 3 separate buildings:
    --> All three buildings are metal frame.
    --> all three buildings have sheet metal on outside (walls and roof)
    --> all three buildings have a dark colored (charcoal) roof metal.. (I think that was a bad choice)

    #1: --> 30' x 30' x 10' (wall height) ... it is our office ... it has 2" of closed cell spray foam on walls and roof.
    ---> this building has an A/C .. (3 ton unit) ... it works great, has been in service for a few years.

    #2: --> our original shop = 40' x 60' x 15' (wall height)... insulation = the 6' wide vinyle backed fiberglass.. has large north and south garage doors, in the summer we leave those doors open ... and we get a good breeze... it is hot in this shop ... but a little sweat.. and the breeze make it bearable ... we have been working in this shop for about 7 years.. and live with it fine... (lots of welding, plasma cutting, waterjet machine, grinding etc...

    #3 --> this shop is our newest .. and the one my question is about.

    --> shop is 30' x 60' x 12' (wall height)
    --> shop has spray foam (closed cell)... paid for 2" .... some places is more ... a few places maybe only 1.5" thick (most probably 2").
    --> This shop has a couple of CNC machines (Mill and Lathe)... they run very clean ... we do not run them often ... they do not generate a lot of heat....

    --> this shop has 1 10' x 10' garage door... it faces the east ... it is a high quality door ... very air tight.. and is insulated... not a lot of opening and closing... it is closed most of the time.

    -- This shop buts up (hard) against the two other shops ...
    > the West wall has no exposure to the outside world .. is against the 40 x 60 ..
    > the North wall ... is against the office shop ... very little exposure to the outside world.
    > East wall ... has 10' x 10' garage door .. and one walk door.
    > Entry to this shop is typically (almost always) from the office area... so no outside doors opening and closing.

    > There was never any intention to Cool this shop with A/C ... we heat it easily with small heater in winter.

    The Problem .... during our "dog days" of summer ... this shop is unbearably hot .... we think we are tough ... but ... July and August (some of June)... it is unbearable .... no breeze (learn value of North/South doors)...

    I would not expect to cool this shop to 72* .... 80 ~ 82* would be fine I think ...

    -- I believe I made a mistake with the choice of roof color .... (dark)... I am looking at having the roof (of all shops) coated with reflective coating (white)... (a roofing system from a local contractor).... I am hoping that will help.

    -- I am going to have more insulation (open cell) added to the ceiling of my problem shop .... and to the top 4' of the exposed exterior walls (bottom 8 ft is not accessible to add more insulation). Going to add 6" of open cell.

    -- I am strongly considering adding Air conditioning to this shop .... Can someone give me an idea of what I should look at or expect for sizing?

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    23,930
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    Unfortunatly we can tell without a lot more information
    Windows
    Doors
    How tight
    Insulation values

    The old rule of thumb was 500 Sq Ft per ton but that's a wild a$$ guess and only in extreme conditions is even close to being accurate.

    30 X 30 with 3-Tons is extreme, I would guess 1-Ton at best

    30 X 60 1 1/2 - 2-Tons

    But there only guesses

  3. #3
    Join Date
    Jul 2019
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    3
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Unfortunatly we can tell without a lot more information
    Windows
    Doors
    How tight
    Insulation values

    The old rule of thumb was 500 Sq Ft per ton but that's a wild a$$ guess and only in extreme conditions is even close to being accurate.

    30 X 30 with 3-Tons is extreme, I would guess 1-Ton at best

    30 X 60 1 1/2 - 2-Tons

    But there only guesses
    ***
    Thank you for your response ... any information is much appreciated.

    I am a little confused by the first part of your response:

    I listed all of the things you specified in the info above:

    > 1 - External garage door ... very good quality door, seals very tight ... it is insulated... dimensions are 10' x 10' ... it is on the east wall
    > 1 - external walk door ... also insulated... also on east wall.... seals good and tight.
    > No windows at all
    > Insulated currently with 2" of closed cell spray foam ... (so very tight) ... I believe that is R13 ... I also have a contractor coming to add 6 inches of Open Cellto the ceiling and to the top 4 ft of walls (the bottom 8 ft of walls in not accessible .. covered by liner panel).

  4. #4
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    23,930
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    Are you on the Gulf Coast, Canadian border?


    There are any # of sites that you provide the data and they’ll run the calc.
    Search Manual “J”

  5. #5
    Join Date
    Jul 2019
    Posts
    3
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Are you on the Gulf Coast, Canadian border?


    There are any # of sites that you provide the data and they’ll run the calc.
    Search Manual “J”
    --- The very first line of my message = "I am located in Oklahoma" ..... we neither have any proximity to "the gulf coast" ... nor to the "Canadian Border".

  6. #6
    Join Date
    Jun 2012
    Location
    Northern NV
    Posts
    1,803
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    Package unit, ground mounted for access, and some really good filters.... a big banks of them much like a paint spray booth.

    Get an installer to size one up and get it ducted... DuctSox is a good alternative for the supplies.

    Would think strongly about a full enthalpy economizer on these so you can get "free cooling" and ventilation air. The ventilation air will be your biggest load I'm thinking. If you do not have nat gas, think heat pump!

    White reflective coating on roof? No-brainer for sure...

    Cheers and coolth to ya.

  7. #7
    Join Date
    Jul 2000
    Location
    Northern Wisconsin
    Posts
    3,008
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    Without being there to see things I would think a simple split system with an air handler suspended at a reasonable height would probably work just fine.

    Make sure you get very good filters installed. Even though the shop is clean, the coolant that does get atomized into the air can coat the indoor AC coil and make it hard for it to get rid of moisture in the building.

    I would put minimal duct work on it because you will more than likely not run it until conditions in the shop are such that it will run a long time and be working against a ton of humidity, both of which can cause standard duct work to sweat and drip moisture off of it.

    I'd look at it and size it more of a central dehumidifier type of installation with a nice side effect of it will also cool the air off. In other words size it maybe a little small so that when you turn it on it will run pretty much non-stop to move air and dry the air out ....... with all the doors closed of course.
    Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.

  8. #8
    Join Date
    Nov 2004
    Location
    SW FL
    Posts
    9,372
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    Thumbs up HEAT GAIN & LOSS ESTIMATE for OK

    NET EXTERIOR Areas and associated R-values are the factors needed
    to determine Heat Transfer

    No windows.

    WALLS
    NORTH, SOUTH, WEST - N/A

    EAST: 60 * 12 = 720 SQ FEET with R-13
    ____ Door 10' x 10'

    Floor: EXPOSED Perimeter, ~ 90'

    CEILING:
    ________ 30 * 60 = 1,800 SQ FEET, use R-30 [ ? ]

    DT: 97' - 77' = 20'F SUMMER
    __ 70' - 17' = 53'F WINTER

    Infiltration: ? / … as indicated

    EXAMPLE: www.loadcalc.net
    _________ _ Sensible Cooling __ _ _ ~ 11,960 BTU /HR for 20'F dT


    Applicability of above values to be verified BY Owner.
    For example, if ceiling is actually R-15: Double the 3,168 BTU/HR listed Sensible Cooling
    ____________________ - - - or recalculate with New value
    Attached Images Attached Images   
    Last edited by dan sw fl; 07-21-2019 at 07:41 AM.
    Designer Dan
    It's Not Rocket Science, But It is SCIENCE with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE

    Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities

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