Insulated Garage and heating options.


I have a garage that is 20' depth x 28' wide and the ceiling is 8' high. The walls are block and the outside I had 3/4" insulation board with furring strips and siding added on for aesthetics. I put 4 new 36" x 36" double pane windows with argon in the garage as well. There are 2 on the east wall and 2 on the west wall. I had ceiling rafters and a i-beam put up as there were only cables holding up the roof rafters. After the ceiling rafters & I-beam were installed I placed R12 or R19 insulation with a covering of plastic over the insulation and ceiling rafters. I then added 3/4" insulation board over that as one side is shiny silver and helps with lighting,not only insulating the place more. After all of this I noticed I got a humidity problem and the humidity levels were near 80%. So I bought a whirlpool 70 pint dehumidifier. I can get the humidity levels down to 48% but no lower. This brings me to the new problem and finding a solution. I live in the northeast of the usa & the weather is getting colder especially at nights. I spend alot of time in the garage and I need heat. At least to 65-69 degrees while Im in there. 55 when Im not. I bought two charmglow propane wall hanging heaters that were 28,000 btu's & open blue flame only to find out that I cannot get them hooked up if I house a vehicle in there. Which I do. So I had to return them. Im looking for a vented propane wall hanging heater for this garage or something that would help heat the place and keep the mositure down and keep the temps mentioned above. I also understand that adding a vent free type propane or gas heater will add to my moisture problem. I was referred to use baseboard heaters but Im concerned on how much it would cost being electric. I probably would use the heat at 65-69 degrees 20hrs/7days a week from October to May(about 7 months). I may turn the heat down to 55 degrees for the night. I was told that electric heat would help the moisture problem(which I would like to stop using the dehumidifier). They also said with gas,propane,& oil prices of today, that electric heating costs arent so bad and are a bit better nowadays. But Im still concerned and still wonder how much heat they would throw off and what the temperature would be using 1,2 or possibly 3 baseboard electric heaters. Anyone have any better advise for me?
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cz snipped-for-privacy@hotmail.com wrote:

In no particular order, just shooting from the hip
Yes.....add some white space & paragraphs to make you posts more readable.
About the heat.....you need to do (or have done) some demand calcs for your heating needs.
determine the source of your moisture problem
Just a WAG but the new windows probably have ~10x the R value of CMU alone. CMU walls without insulation probably have an R less than 1. My guess is that your walss with insulation have an R of about 6?
Make sure the moisture retarder on the insulation is in the correct location....double layers of insulation should not have moisture retarder in between.....onlly one moisture retarder per insulation stack.
With your ceiling & wall insulation & windows installed the weak link is now the garage door?
I'd figure you need something in the 30 Kbtu/hr range or about 8 kwatts to heat when the temp outside is 0 deg F
Inorder to do the tradeoff gas vs electricity............
What is your incremental cost of electricity & oil or gas cost per therm?
My bias is against electric heat IMO it is usually more expensive unless you have cheap hydro power, Electric heat does avoid hte venting / moisture problems but 8 kwatt is nearly a 50 amp draw
cheers Bob
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cz snipped-for-privacy@hotmail.com wrote:

That's 560 ft^2 of ceiling and 768 ft^2 of walls, including windows and doors.

Maybe US R6.

That's 36ft^2/R4(?) = 9 Btu/h-F of window thermal conductance.

They might collect 0.5x36x415 = 7470 Btu of sun on a 30 F Jan day in Phila. What's the south wall like? You could glaze south doors like this:
http://builditsolar.com/Projects/SpaceHeating/SolarGarageCollector/garcol.htm
A 28'x8' tall version might collect 0.9x1000x28x8 = 201.6K Btu and lose 6h(T-30)28x8/R1 when the doors are open + 18h(T-30)28x8/R6 when they are closed. If the rest of the garage loses 24h(T-30)116 through the ceiling and non-south walls, T = 74 F, over an average January day.

Cables holding up roof rafters?

... 560ft^2/R25 = 22.4 Btu/h-F of ceiling conductance.

No vapor barrier under the floor? Paint it?

You might run it for heat and pipe the exhaust to the outdoors and run tools from an inverter, with a CO detector...
If the south wall has no doors, you might cover it with 28'x8' of U0.58 Thermaglas Plus twinwall polycarbonate ($85/4'x12' sheet from Palram at 800 994-5626) with 80% solar transmission and collect 0.8x1000x28x8 = 179.2K Btu on an average January day. If the air behind the twinwall is T (F), it would lose about 6h(T-30)28x8xU0.58 = (T-30)780 Btu during the day and 18h(65-30)28x8/R7.7 = 18.3K Btu at night. The windows and non-south walls might lose 24h(65-30)116 = 97.4K Btu/day. The ceiling might lose 24h(T-30)22.4 = (T-30)528 Btu/day. Putting this all together, you could make an average ceiling mass temp T = 84.3 F.
If sun-warmed air keeps the garage 70 F for 6 hours on an average day and you store 18h(65-30)154 = 97K Btu of overnight heat and the thermal mass in 508ft^2x5 = 2540 Btu/F of hollow blocks (which would work better with holes at the top and bottom to allow room air to move through the blocks) stores (70-60)2540 = 25.4K Btu, you need to store 97K - 25.4K = 71.6K in ceiling mass. If C Btu/F cools to 60 F by dawn and warms to 60+2(84.3-60) = 109 by dusk and (109-60)C = 71.6K, C = 1473, eg 13 4"x20' thinwall PVC water pipes under the ceiling, with a slow ceiling fan and a room temp thermostat and an occupancy sensor to keep the room 70 F as needed.
On cloudy days, you could circulate hot water up through the pipes from a large well-insulated heat storage tank to heat the garage.
Nick
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Since it sounds like you do automotive work, check into a "used oil heater" on ebay. I found a couple of them there. You can burn all used motor oils up to sae-50. You can also burn transmission fluid. It is usually a pain to take the stuff to a recycling point. Now you can collect it during the off season and burn it during the cold season!
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One of the components of propane is water and burning it, of course, makes water vapor.
I was referred to use baseboard

A 1500 watt electric heater will give you 5,000 Btu of heat. You probably need 20,000 to 30,000 Btu to get the temperature comfy on a cold day. Given the part time use, they will probably be operating much of the 20 hours that you want heat so you can figure the cost by multiplying the kW by your electric rate.
I'm not sure of the codes on gas heaters. I do know that in some places, gas hot water heaters are put into garages but must be 18" off the floor. I'm also wondering what mechanics have in their shops. Of course, any open flame in any place that has gasoline and solvents can be a danger.
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cz snipped-for-privacy@hotmail.com wrote:

Something like this from a previous post?
http://shoppingcart.msservicecompany.com/default.aspx?ext=true&itemid=sa25ng
Should be a number of sources for similar units, looks like it installs pretty much like a through wall air conditioner so pretty easy to deal with.
Another option if you increase the insulation to decent levels so electric isn't too expensive, is one of the heat / A/C units designed for hotel / motel rooms so you get your heat and A/C all in one simple package.
Pete C.
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Your windows are likely R3. 3/4 pink or blue foamboard is only 3.75R, so your walls are underinsulated. Your area is large with the poor R value and air infiltration of the garage door. Your concrete floor will hurt also and add alot to your load. Your dehumidifier may not be a design to operate under 60-65f without freezing the coil, even if it is a model that will operate in colder temps its efficiency goes way down as it gets colder. A small gas furnace or vented wall heater will do, but you need a load calculation done as you will likely need 20-35000 btu. Forget electric as im sure its Btu cost is more than gas, but you need to run your own BTU comparisons for different fuels. Heating 20 hr a day will cost alot. A wood stove can put out alot of btu, a radiant electric heat can give warmth if you work in one area. A small Ng wall heater or furnace might be best after you insulate more. But have a load calc done, the BTUs needed will suprise you.
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Solid fuel stove are not allowed in attached garages though.
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You didn't mention where you live or how cold your climate (e.g., big difference between Seattle, WA and International Falls, MN). Likewise, it would be helpful to know the cost of propane and electricity in your area --- whether you pay 5 cents or 15 cents per kWh has a direct bearing on matter. Without this information, we're really only throwing darts in the dark.
Is there any insulation below the slab and around the perimeter of the foundation? If not, your garage floor will remain cold and leak a tremendous amount of heat into the ground. Moreover, 0.75 inches of wall insulation for a heated structure (especially one heated by electricity) strikes me as rather modest in just about any climate (I'm guessing something in the range of R3 to R4?).
As a point of reference, electrically heated homes here in Nova Scotia generally have between R38 and R60 insulation in the ceiling and R20 and R28 in the walls. There would be a minimum of R10 insulation around and underneath the slab. According to our provincial department of energy, a "typical", new electrically-heated home uses 15,000 kWh/year for space heating purposes; adjusting for the smaller size of your garage, that's perhaps 4,000 kWh/year. These numbers, of course, reflect our climate and insulation standards. As a wild guess (and please treat it only as such), your energy consumption could very well be two, three or even four times that.
Sorry I couldn't be more helpful.
Cheers, Paul
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cz snipped-for-privacy@hotmail.com wrote:

Simply go to propaneproducts.com and check out the Modine HotDawg heaters. I have used Modine heaters in shop environments since about 1974 and those units are still up and running today. At the present time I have a new residential garage (central Illinois) and plan on using the HD 40,000 BTU for heat. The price/performance is just right, and conversions from propane to NG are easily done. With a Honeywell programable thermostat you'll have an unbeatable combination.Highly recommended.
Joe
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Your wall insulation sounds a little inadequate, especially for the Northeast. I live in Washington state, and put R19 in my garage walls and ceilings. Even that's a little light on a cold winter day. Remember a lot of heat will be lost out your garage doors!

I'm not sure what kind of work you do in your garage, but baseboards are usually not a wise choice because of dust build-up. Could be a fire hazard if you don't clean them often.
On the other hand, any kind of combustion heater (propane, natural gas, etc.) will have to be located at least 18" above the floor by code, to protect against igniting fuel vapors from cars.
Personally, I'm a big fan of electric heat, but we also have reasonable electricity rates.
The general rule of thumb is 10 watts per square foot, so you would need about 5600 watts to heat your garage. That's about 24 amps at 240 volts, so you would need at least a 30 amp circuit in your garage for the heat.
That said, I use a small 4000 watt "Cadet Hot-One" to heat my 24'x28' garage. It's really undersized, and runs almost all the time, but it keeps my garage comfortable enough to work in while I'm out there. If I wanted to heat the garage full time, or just wanted it to warm up quicker and stay warm, I could simply add a second heater. Since I only use mine occasionally, I just set my heater on the floor with a dedicated wall outlet. But, the Hot-Ones can be wall mounted too.

A 5600 watt heater running continously for 1 hour would use 5.6kwh. Of course, the heater shouldn't run continuously, so that would probably drop to about 2kwh per hour or so (assuming it runs about 20 minutes each hour). Running 20 hours a day, that would translate into roughly 40 kwh per day. Multiply that times your electric rate to see what your cost per day would be.
Around here, that would be 7.4 cents * 40kwh, or roughly $3 per day.
Of course, the less insulation you have, the faster the garage will cool down, and the more the heater will run. Improve your insulation and the heater will run less, saving you money. Don't heat the building when you're not in it, and you'll save even more.
Anthony
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On 13 Oct 2006 23:18:09 -0700, cz snipped-for-privacy@hotmail.com wrote:

Do you live anywhere where you could get away with a mother-earth-news style waste-oil heater?
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Well thanks for all the replies. I appreciate the help and information. Sorry if I miss anyone's questions. And after reading all the replies I see I have left out some information too. I have forgotten to mention I have a insulated 9x7 garage door and its steel both sides with insulation in between. So its the warmest one I could afford.There is no windows in it as well.
I do have the floor painted.
This garage was built around a previous smaller garage and the guy didnt want to tear the old existing garage down so cables were used to run across the building east to west where your ceiling rafters would usually be with of course lolicollars near the peak of the roof on the inside. There was also a drop ceiling in the place but I replaced all that now. There was a bit of movement after 33 years but nothing major. The cables held the bottom of the rafters quite well. But heating a place with that high of a ceiling and having only a drop ceiling in there wasnt a good way to keep heat in the place.
I figured the place would be under insualted for electric heat. Glad I asked though. I did more research on it and you guys are absolutely right. R-38 is needed or something similar. I was told it was a good way as long as the place is well insulated. I thought about placing more insulation in the ceiling but come summer I imagine Ill have the same situation only too much heat and not enough cool air. lol! I dont want to add a air conditioner. Not yet at least. I get a very nice breeze with the 4 windows and the garage door open and only needed a fan on low to circulate the air this summer. It wasnt that bad. Ill see how it goes next year and decide then.
I finally found information on northern tools how to determine how many btus would be needed after some of you guys told me to do a load calc. Thanks again. That helped and I hope Im right.
But according to the way northern tools explains 1-you simply multiply lxwxh to get the total cubic ft. My case would be 4480.
2-Then figure the temperature increase by the heater and subtract this by the area temperature with out the heater. I figure take the lowest temperature that it was during February-March(the place was already insulated,sided,new roof,etc in February of this year) as a rough estimate which was proabably 35 but Ill say 33 just to go under a bit. We had some cold days and nights I remember and it may have gone to 33 but didnt go below freezing. As long as I get 60-65 heat I would be satisfied. I dont like it too hot. Room temperature increase with heater 69 minus lowest temperature on a cold night 35 equals = 34.(this part doesnt make sense to me). Step 3 I found easier.
3- They state to calulate the btu's required to achieve the increased temperature take the 4480 (total cu.ft.) x 1.33 = 5958.4 x that by increase temperature desired with the heater. Which if my coldest night was 35 or 33 and I want 65-69 degrees inside. There would be a 30-36 degree difference. Which would come to 22,000 btu's. I think I would just look for a 30K unit.
The other problem along with moisture, and finding a unit, is I have a store credit with the home depot. So I was trying to stay with purchasing at that store so I could use the store credit up.
I did find a 30K unit that I think I can use.
http://www.homedepot.com/prel80HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE=PROD_META&MID76&com.broadvision.session.new=Yes&N)84+3693&No&CNTKEY=misc%2fsearchResults.jsp
Its a direct vent unit with thermostat. The unit comes with material for venting a 9" wall. Its a sealed combustion chamber.And it comes in propane or natural gas. I wanted to go with natural gas but my town does not have natural gas lines in my area nor do I think its offered anywhere in the town. Ive seen only propane tanks. Is there anything I can do or add on to the unit to cut the moisture that propane gives off? Also does anyone know for sure if I can use this heater with a vehicle in the garage? After buying two open flame heaters and having to return them I would like to get all this settled before I use the store credit for anything.
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You seem to be missing something important:
Moisture is only an issue with propane (or natural gas or oil) when the unit vents _into_ the building. Eg: portable, "ventless" units.
A propane or natural gas or oil unit that vents to the outdoors will NOT be a moisture problem.
You're talking about a pretty high duty cycle (7x20). In that case, it's particularly important that you DON'T use a ventless unit - not just because of moisture, but because of the potential for CO.
Certainly for a situation like that, don't use an occasional-use portable unit.
You seem to be looking at a vent-type NG unit. Good. It's probably convertable to propane, and as it's vented, it won't be a moisture generator.
Electric is often preferable for occasional use because it's so cheap to install it'll offset the (usually) higher operating cost. But as it's not cheap to operate, it doesn't make sense for a duty cycle like Oct->May 7x20 _especially_ with how poorly insulated the building is.
[My garage heat is electric. But it's quite well insulated, and it operates only for perhaps a day per winter month.]
--
Chris Lewis, Una confibula non set est
It\'s not just anyone who gets a Starship Cruiser class named after them.
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P.s. I really dont have the room for a oil furnace,oil tank. :(
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