BTU required?

[Greatwhitewing]

I have a garage that is a metal framed canvas covered temporary structure so about ZERO R value. 2 car garage sized Cover-It brand with partition wood ends and sliding doors each end. I live in the peoples republic of taxachuesetts so a permanent structure with a variance was too much effort if even possible.

I would like to heat a small working area about the size of HALF a car and nearby work bench area to 10-15 degrees (F) above ambient temps while I do needed repairs and maintenance on my vehicles. Wind effects are minimal.

How many BTU's do I need and what type of heater design is best for my scenario?

Since I don't have a lift having the heat partially directed under the car and to the nearby work bench is pretty much a requirement.

 

[Kev442]

I would use a Mr Heater propane radiant heater.

 

[Greatwhitewing]

Any idea what size I would need to get the 10-15 degree rise over ambient?

I would use a Mr Heater propane radiant heater.

 

[rlitman]

The great thing about radiant heaters, is that they heat YOU more than they heat the room. Forget about heating over ambient with them, but at least you'll feel warm (although any metal tools will still feel quite cold).

You can always get a torpedo heater, and get it roasty toasty in there, but the smell can be pretty bad.

 

[lzenglish]

Any idea what size I would need to get the 10-15 degree rise over ambient?

To find the size you need, a heat load calculation will need to be done, unless you just want to ball park it. The easiest way to do this, is call a couple of HVAC contractors, to come out and give you a free estimate to install one of "their units". Or, you can get a copy of a short ,or long form heat load calculation form, and figure it out yourself. This is nothing more than filling in the blanks, concerning your sq. ft., insulation, windows, and weather temp. conditions, etc., in your area. Then you add it all up, and add a small percentage for unforseen weather conditions, and or future add on's, etc.

Wayne

Edit: Woops, I over looked your canvas roof, untill I see "69pace's" response. I don't think you will find that parameter in a heat load calculation, so ball park is what it looks like to me. Find a space similar in your area, "as stated", and see what they are using to do the job.

 

[69pace]

For what it is worth, many nurseries have temporary greenhouses that are nothing more then bent ribs covered with a poly barrier. Within them they use a standard natural gas air exchanger or forced hot air oil burner that uses a poly vent tube that has holes every foot of so to distribute the heat at the top. You might take a look at these units. The key for you would to put a taped and sealed vapor barrier under the canvas, then seal the bottom to the ground with sand bags. Once the structure is wind tight you can heat it easily with electric or gas or solar. You have a few commercial options, Mr Heater / Big Maxx as suggested, or radiant electric on the floor, or a standard green house electric or gas heater. http://www.advancegreenhouses.com/greenhouse_heaters.htm

 

[Greatwhitewing]

That might work out fine in the spring when I have to replace the "canvas".


"The key for you would to put a taped and sealed vapor barrier under the canvas, then seal the bottom to the ground with sand bags"

 

[Gary S]

You can't know BTU required until you know the rest of the story. What is your BTU loss? What temperature do you expect to have inside? What temperature is it outside.

The answer to any equation isn't available until you plug in all the variables, and the internet will never replace good old fashioned math they taught us in school.

 

[NUTTSGT]

You have what amount to nothing more than a military mechanics tent. I don't think it will ever be "warm" but it could be comfortable compared to outside temps. You won't have a biting cold wind or snow to deal with, that will worth alot alone itself.

I think a 55-60K btu space heater would be fine for that canvas hut.

 

[ForceFed70]

I would also reccomend a radiant heater. Forget about heating the building and just heat the workbench/person.

You might try a 1500W electric radiant heater 1st before spending big bucks on a gas heater.

 

[Charles (in GA)]

I assume this is one car size with just enough room to get around it.

Put a torpedo heater outside blowing in thru a hole in the end wall. Use metal or something non-flammable for the hole. This way the heater will be drawing outside air thru, heating it, and discharging it inside. Yes, it produces fumes and Carbon Monoxide, but you will be getting a major air change from forcing the outside air in. Get fresh air at the first hint of a headache or nausea. You could use a CO detector also. Burn Kerosene (K1) in it and it will not smell too much, Diesel is fumey, Jet A is even cleaner burning than K1 and probably not more expensive. Some airports won't put it in anything but an airplane, others don't care, and some are self service, even the jet is self service). I would use 65K to 85K BTU or so.

Another option would be a Kerosun type wick heater, elevated to keep it from any potential fuel spills. They put out a surprising amount of heat, are silent and if properly adjusted burn very clean with little to no CO. Not as effective as a torpedo heater but not as loud and not as dangerous as a torpedo/salamander heater.

Dress warmly.

Charles

 

[dave67fd]

I agree with Charles. Being a temporary uninsulated structure, installing any kind of costly more permanent heating system is foolish.

 

[rlitman]

You might try a 1500W electric radiant heater 1st before spending big bucks on a gas heater.

I've got one of those. It's better than nothing, when I'm within 6' of it, but just about worthless when I'm off-center, or more than 6' away.
1500W translates to just over 5000BTU/h
I used to have an 8000-14000BTU/h MR Heater radiant propane heater (a single circular heater that sat on a 20lb BBQ tank.
Doing an oil change and a little more a couple of winters ago, I had one on each side of me on a breezy 20F night, and it was comfortable, but under the car, it was still pretty cold (I couldn't point the radiant heaters down, and I was in the car's shadow).
Nowadays, I just point the 55kBTU torpedo heater at me from about 6' away, and the whole area is toasty, even outside.

 

[Greatwhitewing]

Exactly the type of direct experience I was looking for. Komal Tada (Marshallese for TYVM probably spelled wrong)

I've got one of those. It's better than nothing, when I'm within 6' of it, but just about worthless when I'm off-center, or more than 6' away.
1500W translates to just over 5000BTU/h
I used to have an 8000-14000BTU/h MR Heater radiant propane heater (a single circular heater that sat on a 20lb BBQ tank.
Doing an oil change and a little more a couple of winters ago, I had one on each side of me on a breezy 20F night, and it was comfortable, but under the car, it was still pretty cold (I couldn't point the radiant heaters down, and I was in the car's shadow).
Nowadays, I just point the 55kBTU torpedo heater at me from about 6' away, and the whole area is toasty, even outside.

 

[trainer]

Small woodstove with a chimney out through the wooden end of the structure.
For working under the car, get a piece if styrofoam sheet to kneel/sit/lay on.

 

[Jagmandave]

Are there any "rent a shops" in your area?

One just opened locally here that rents for only about $10/hr - $20 if you need a lift, and they provide the tools. Indoor, clean, well lit, includes tools, has heat for winter and A/C for summer......seems like a real deal if you don't have a garage of your own.

The reason I mention it is that it seems to be a franchise deal....the one here is called DIYAutorepairKC.com, there may be one in your area too?

Worth checking out, nothing harder than trying to do quality work with frozen fingers or sweat running into your eyes....

 

[Greatwhitewing]

It's not just auto work but a variety of projects including wood, small appliance repair and whatever needs doing as a homeowner. The garage idea is a good one since I don't have a lift, just ramps, jack stands and floor jacks

I am leaning towards the propane torpedo heater. Debating (in my shallow mind) between the 30-60kbtu and 50-85kbtu units from Mr. Heater. I have smelled those kerosene heaters before.

Are there any "rent a shops" in your area?

One just opened locally here that rents for only about $10/hr - $20 if you need a lift, and they provide the tools. Indoor, clean, well lit, includes tools, has heat for winter and A/C for summer......seems like a real deal if you don't have a garage of your own.

The reason I mention it is that it seems to be a franchise deal....the one here is called DIYAutorepairKC.com, there may be one in your area too?

Worth checking out, nothing harder than trying to do quality work with frozen fingers or sweat running into your eyes....

 

[trainer]

The problem with a propane heater is that it puts alot of moisture into the air that will condense off of the cold surface on your cover and drip all over everything.

 

[rlitman]

Water is not specific to propane. Kerosene does the same thing. Any unvented heater actually. Propane does however produce a higher ratio of water to CO2 than kerosene (about 1.3:1 for propane vs about 1.1:1 for kerosene, with methane being 2:1). The lower carbon content is why propane burns cleaner (there's less CO as well, because of this), and why natural gas burns cleaner still.
Would you rather be breathing water vapor, or increased CO2?

I will admit that after using the kerosene torpedo heater, I have to shower when I come back into the house. The smell lingers on your clothing (that's one reason why I have "shop" clothes), and especially in your hair.

Other people on here have complained about the smell from propane torpedo heaters. They're not kerosene, but they're not odorless either. I do have a friend who's happy with his though.
The catalytics are odorless for all intents and purposes, but don't put out enough to truly heat your space (just increase your comfort level a bit).