Heating AND Cooling workshop/garage?

Discussion in 'Workshop Tips and Secrets / Tools' started by cattflight, Jan 17, 2011.

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  1. Jan 17, 2011 #1

    cattflight

    cattflight

    cattflight

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    Hey gang.
    I have a tandem 3-car attached garage (right hand side is 2x as deep as the main garage and the main area is approx 18x18) for a total of approx 525 sq ft with 11' ceilings. The garage is sheetrocked and I am assuming it is insulated but I am not the original builder - but logic says it should be. Concrete slab floor and foam panel insulated door with the Master Bdrm overhead.

    I plan to do most of my composites construction in the tandem right side and "stage/prep" my work on portable benches on the left hand side so I can still park my wife's car inside at night. Here in south Denver, we get winters where the temps can get as low as 35F and as high as 95F in the garage, but those are few and far between. Typically, garage temps will vary between 50F-85F, but that's still outside the range I want or can tolerate with composites. So I am looking for efficient ways to bring the temps up quite a bit and down a few degrees when necessary. I suspect my heating months will range from Sept-May and my cooling months from July-Aug only (not uncommon to see 30F-40F swings overnight here, even in the summer)

    So....any recommendations would be helpful, but I am thinking of a portable swamp cooler like this one. I am wondering if this might create more humidity than I want. It's already very dry here in Denver, with RH between 40-68%, but not sure what these units will do to that. Also not a clear spec on what type of temps drop I should expect with this unit. Anyone know how to calculate that?

    For heating, I am trying to avoid anything with an open flame, but I also don't want something with a fan blowing dust around. Thinking about an electric infrared radiant tube heater like this one. Figured I could install 2 or 3 on their own switches so I can heat the garage quickly but maintain only the areas I am working in. My main concern with these is how "localized" the heat might be and if I would end up creating "hot spots".

    Oh, and one last thing....I would like to do this in a "non-permanent" installation. With the exception of some 240VAC power I plan to install anyway, I really don't want to start piping gas and venting through the walls.

    OK. Let 'er rip! Am I on the right track? Any specific experience with these types of units? Thanks!
     
  2. Jan 17, 2011 #2

    autoreply

    autoreply

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    "Poor man's painting cabin" might be an idea for you. Weld a 17X17 steel frame. Hang transparant plastic from it all the way to the floor and cover the top with it. With a couple pieces of rope you can tie the whole thing to the steel frame, hanging on the ceiling.

    As for calculating power; if you have the surface area and the isolation specifics of the area it's fairly simple; materials have a "heat flow":
    Thermal transmittance - Wikipedia, the free encyclopedia

    With a construction like a garage that might quickly become complicated.
     
  3. Jan 17, 2011 #3

    Hot Wings

    Hot Wings

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    These portable coolers just don't work. Sure they blow cool air out the front but in an enclosed area they just raise the overall temp and humidity. In a large shop they have some value for local cooling.

    What kind of heat does your main house have? If it's hydronic just plumb in an extra zone and radiator, but I suspect you have the more normal antiquated forced air so common in our part of the world.

    Radiant heat does work but I hate standing under it so I've never tried it with composites. I suspect that it could cause working time problems.

    If you're going to be rewiring for 220V I'd look into the window mount heat pumps like are used in motel rooms. In a well insulated area of the size your considering they would probably be the best solution. They can be very energy efficient, they are compact, and they both heat and cool.

    Window A/C/Heat Pump, 24K/23.6K, 230/208V - Window-Wall AC & Heat Pumps - Air Conditioners - HVACR : Grainger Industrial Supply

    No building permit needed, other than for the wiring.
     
  4. Jan 19, 2011 #4

    Topaz

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    Keep it simple.

    Cooling: Swamp coolers are a poor solution, IMHO. They're better than nothing, but not a lot. Go get one of the portable air conditioners - such as this, for example. (Not recommending a particular model. Read reviews to find a good one.)

    Heating: IIRC, radiant heaters are not recommended for composites work. The infrared can cause hot spots on your parts if they're too close. A convection heater is better, such as this. I have one very similar to this (different brand) for my own garage and it works great.

    Limiting the volume to be climate-controlled like Autoreply mentioned will help the effectiveness of these devices.
     
  5. Jan 19, 2011 #5

    roverjohn

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    Google "mini splits cooling". They are what you are looking for and have seer ratings over 20 now and operate as heat pumps when that's what you need.
     
  6. Jan 19, 2011 #6

    cattflight

    cattflight

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    Thanks guys. Your feedback is greatly appreciated.

    I was afraid the radiant infrared heater approach would create hotspots. I will look into these other recommendations. I am a big fan of the portable units because, as autoreply recommended, I plan to "curtain off" sections of the garage so I can have a 15x10 area for small work, a 35x10 area for wingspan and hull work, or the full 500+ sq ft.

    I also just picked up a digital thermometer from HD that will allow me to record actual min/max temp readings as I haven't truly qualified the range of temps throughout the year. For all I know, I might not really need A/C, but at the moment I cannot imagine that's the case.
     
  7. Jan 25, 2011 #7

    Trackwelder

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    By the time the radiant heaters bring the concrete floor up to temp, it will even out real well, plus you don't have the open flame of regular furnaces. A regular furnace must be at least 18 inches off of the floor in a garage, but duct work in that size is optional. Ask an HVAC installer what they have that would be good for a garage unit, the guys on the truck not the company. They will likely be able to set you up with heat and Central air for less than the cost of a new furnace alone. I wuld love to take a trip out to Denver and have several units here, but check locally you could do just as well. depending on how far gas and electric lines have to be run you cold be looking at less than $1,000.
     
  8. Jan 25, 2011 #8

    Vigilant1

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    I agree with HotWings' suggestion regarding the window-mounted heat pump. It heats and cools, has no open flame. You don't say what type of budget you are on, but I'd definitely look for a used one--new units are pricey, and servicable used ones are widely available (hotels typically upgrade all their rooms at once, so servicable used units are junked.)

    You might want to check to be sure the walls in your garage are really insulated--they often aren't. It's cheaper to insulate the garage ceiling and any common walls to the house, so that's what builders often do. Drill into a stud bay with a small bit, insert a coathanger with a small hook bent into the end, and pull it out. You'll either have fiberglass insulation on the hook, maybe cellulose, or (worst case) you'll be staring at an empty hook and swearing at your cheap builder. After you find that out, you can do a "heat and cooling load calculation on your garage to see how many BTUs of heating and cooling you'll need to get the temps you want (given your anticipated outside temps). The gold standard for these calculations is something called a "Manual J" assessment. But, I used this online calculator to do calcs for my house and my stand-alone shop and it worked great. It will take you 20 minutes and youll know how big the heater/AC will need to be without guessing. If you have 16" stud spacing and fiberglass insulation filling the cavity, then your total wall R-value is about R-12 (this accounts for the thermal bridging of the studs). If you have no insulation in the stud bays, you have a total wall R-value of about R 4.6. If you are lucky enough to have 1" foam sheathing outside the studs and 3.5 inches of fiberglass insulation, you have a total wall R-value of about R-20. When you use the calculator, be sure to account for any walls/ceiling that are against conditioned spaces in you home, since they won't be leaking any heat.

    I was lucky enough to be able to build a shop, and I knew I wanted to heat and cool it affordably. I insulated it well (easy to do at the time of building). The shop is about 30 x 24', and I use a regular home AC window unit (10K BTU) to keep it comfortable in 100 degree weather. Heating is done with a regular small domestic gas furnace (45K BTU) that I got for $100 at the Habitat for Humanity recycling store (you can bet I checked really well for leaks in the heat exchanger! And, I have a CO detector running all the time in the shop--cheap insurance). Everything works great and the heating/cooling hardware cost me less than $300.

    Open flame: What are you specifically concerned about (Trying to avoid an ignition source for flammable gasses/dusts? Trying to avoid introduction of combustion byproducts into work space? etc). Depending on what you find regarding insulation and what your heat load calculations show, it might prove to be a challenge to heat your area using electricity (both due to available electrical capacity and utilities cost). Composites require warm temps, your epoxy won't be happy at 65 deg F. If you've got natural gas at your house, using it heat your workspace might be a good answer. The "vent-free" furnaces are cheap and put out a lot of heat, but they also add a lot of water to your inside air and have a definite open flame. I'm not a big fan of them--they are illegal in many countries. You could also use a conventional furnace, which would not exhaust any combustion products (incl water vapor) into your work area, but a flame would be present and accessible to the air in your work area (since that's where the combustion air comes from). Lastly you could install a small "through the wall" closed combustion furnace/wall heater which gets combustion air from outside and vents to the outside. They aren't rock-bottom cheap, but they are efficient, fairly easy to install, and avoid the open flame you mentioned. I realize all this contradicts the preferences in your OP about avoiding new gas plumbing and installation of new vents, but you might want to keep that option open--it's not that hard, you'll be in this area a lot and being comfortable is important, and making permanent changes will also permanently increase the usefulness of this workspace after you finish your plane, and maybe even add a little to the value of your house. Heck, Denver gets snow and ice storms, and power can be out for days. In a real pinch, you might feel pretty happy/smart to have a spot you could keep warm with natural gas if the power went out (some of the smaller NG heaters can run with/without a fan).

    I don't think you'll be happy with a swamp cooler. They do work reasonably well in places like Denver, but the extra moisture they put into the air won't be good for your epoxy work (blooming, etc).

    Good luck!
     
    Last edited: Jan 25, 2011
  9. Jan 26, 2011 #9

    Dana

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    A friend of mine heated his garage with a wall mount propane heater (the vent free kind, that exhausts into the room and adds water vapor). They also make them in direct vent (through the wall vent) models. They're natural convection, though my friend's has an aux fan.

    When I bought my house, the previous owner had an old mobile home furnace (forced hot air, about 18" wide by 6' high) in the garage, running on kerosene from an old outboard motor gas tank. He took it with him, but a few years back a friend (the same one mentioned above) upgraded his house furnace and gave me the old one. It's a hot water boiler... I plumbed it to an old car radiator with a fan blowing through it, and I use antifreeze so it doesn't freeze when it's off... it can heat my garage from 0°F to 70°F in an hour or so. I run it on kerosene from a 55 gallon drum.

    At one time I had a window air conditioner in the garage window, but it's not that big a deal to me.

    -Dana

    The Bill of Rights goes too far--it should have stopped at "Congress shall make no law".
     
  10. Jan 26, 2011 #10

    Vigilant1

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    That's another way catfight could heat his garage inexpensively if he's got a NG water heater. Just run a 3/4" line from his water heater "out" pipe to his garage to a suitable heat exchanger, with a small circulating pump pushing it back to the "in" pipe at the water heater. The long runs could be easily done with PEX, and the heat exchanger would have to be good for potable water ( these panels might work, note the conversion chart for lower than 180 deg F water temps, typical home water heaters are 120-145 deg). I don't know what they cost. If they are expensive you could always make a fun project out of this by making your own heat exchanger with a lot of 1/4" soft copper pipe, something for additional heat-exchange area, and a fan. A single thermostat switch could turn the fan and the circulation pump on and off.

    There. Heat for the garage done at natural gas prices but with no new gas lines or flues. A typical NG water heater runs at 35K to 75K BTU/hour, more than enough to keep ahead of any reasonably-sized heat exchanger and to heat a small garage (IF it is insulated).
     
  11. Jan 29, 2011 #11

    Lemans

    Lemans

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    Don’t forget about existing « green » technology.
    It’s worth the effort.
    The length of the tube under the surface depends on the volume of your workshop.
    If you are able to get some mass into the shop, temperature will vary less on daytime basis.
     

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  12. Jan 29, 2011 #12

    Vigilant1

    Vigilant1

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    Yes, unfortunately people still propose doing this for cooling, too. What happens is the incoming air gets lowered below its dew point in the underground, dark pipe and condensation results. It makes a groovy mold colony.
     
  13. Jan 30, 2011 #13

    Lemans

    Lemans

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    I have build several “green” houses in the past and the system is widely accepted in Europe. As mentioned, you can use is to pre-heat and to cool your house/workshop with it. You don’t need to overestimate the danger of the water in the pipes caused by condensation. You do need a system to evacuate the water, in general a small water pump.

    What you get is more important for your health. Every 4 hours the air is refreshed so chemical vapor from curing resins is evacuated constantly. If you do it by the book, you will have a workshop with a relative constant temperature and a very small energy bill.

    A few words about the heat exchanger. You don’t need one ‘factory build’, an isolated wooden box with aluminum tubes will do the trick too. If needed, I think I’ve still have some plans for a home build system. I used 4 small computer fans as blower.

    Ps; In most cases, green houses are not green at all…the money saved is spend on buying fuel for other ‘applications’ .But hey…what is wrong with that? ;-)
     

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  14. Jan 31, 2011 #14

    johnnyd

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    Keep your eyes open for a used mobile home/trailer unit. They can be had pretty cheap & are the same as a central heat & air unit, only smaller. Should be a good size for garage/shop use.
     

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