Soda can garage heater

Since this is my thing, and since everyone's entitled to my opinion , in order of cold weather comfort and efficiency for a garage:

1) In-floor radiant heat. There's nothing better, nothing more comfortable, and nothing else compares. Work in your shirt-sleeves. Lay on the floor. It's wonderful. the drawback is that you have one chance to do this-- when you are building the garage. If the pipe isn't in the floor, you're screwed.

2) Forced air gas heat. The space heats up quickly, and is pleasant to work in. Laying on the floor gets cold, but at least you're warm everywhere else.

3) A woodstove. It does nothing for you when you aren't feeding it logs, but when you are-- the heat is pretty darned nice. Drawbacks-- it's an open flame. At least it vents outside.

4) Infrared heat. The idea is to warm objects under the heat-pipe, not the air around it. It's a nice theory, but stuff "in the shade" not in a line of sight under the heat-pipe gets no heat. Working under a car is not in the line of sight. It requires a gas line, and really isn't all that comfortable. 

4) A heat-pump. The only advantage here is that it runs on electricity. The heat is really uncomfortable-- mildly warm(ish) air blowing around the room (nearly) constantly.

5) Electric heat. It's a nice heat, but get out your wallet-- there's nothing cheap about heating with resistance heat.

Unacceptable-- any ventless heater, propane or natural gas. It's dangerous and stupid. I did it on one of my places, and will never do it again. A good way to get kidney or brain damage, or suffer with a lifetime of autoimmune problems.

In order of preference for fueling whatever you do:

1) Natural Gas. North America (the US and Canada) are the Saudi Arabia of natural gas. The commodity itself is almost free. What you are paying for is the cost to get it to your house.

2) Wood.

3) LP. It's #3, but I'd put this about 8 rungs under natural gas if there were 8 other things to put in between. There's not, so here we are. Get a big tank.

4) Electricity. It's just expensive.

Thanks Stan for putting things into perspective, the autoimmune problem mention is especially interesting.

Stan have you heard of pouring two&1/2 inches of concrete on top of your existing slab to cover pex tubing.

I stayed in a small casa B&B in New Mexico once in the dead of winter and it had radiant hot floor heat (floor was tile) and that was THE BEST, as Stan has said.  I have no idea about economics here (capital investment to get it, fuel costs to make it work, etc.) but padding around in shirt sleeves and socks was the bomb.  And it was like zero outside.

My two car garage is insulated and has dry wall and shares two walls and part of the ceiling with the house.  It is on the north and west side of the house, so has zero solar exposure. The double size garage door does not fit especially tightly, and improvements could be made there. I have a 220 v space heater, fan forced, not sure of Btu rating, which will take the chill off in just about any weather. It is only about 16" square by 4 " deep, and so can be moved about to aim at where you are.  It ain't perfect, but it does allow for winter work in the garage.  Give it 30 - 60 mins before you want to go in there.  Future plans call for one of those motel heat pumps (called splits) that will heat or cool.  Methinks this could do the job well enough and even help out in the summer.  Sometimes the sweat running into your eyes can be a real PITA.  East Coast Bruce has one of these in his garage, and I think it works pretty well.  Cost to run?? not sure, but is easy electric hook up, so there is that.

I just thought of one thing that I would like to see what Stan thinks about and that is if you have a radiant heat system but instead of natural gas you have a dedicated electric water heater say 40 gallons would that be much less efficient if Gaz is not available.  Also would you need to put in propylene glycol?  Just wondering.

@IaM-Ray,

I've heard of retrofit in-floor jobs being done, but I've never been a part of one. One drawback I can see is the need for an insulation barrier under the concrete. Some guys are using thin reflective insulation sheets as the barrier when pouring on leveled grade (I'm not a fan), and it would be wise to do at least that with your idea of 3" of concrete with the pipes on the bottom. I've always used 2" of foam-board under the concrete, but you play the cards you're dealt.

You'll want to be on 1 ft centers with the piping. I've used 3/4" PEX on every job before my house (I used 1/2" PEX on the floors in the new place). I've had 5x the issues with the smaller PEX and pump sizing as I had with the bigger. If I had it to do again, I'd put the bigger PEX in the floor. Loops are easier to lay out (since the allowed runs are 500 ft vs 300 ft), and the pump head is much lower. In a retrofit application, I'd probably use 1/2" just to keep the pipe profile smaller and the pipes in the (thin) concrete.

Propylene glycol is a good idea if you have any worry about freezing, but like most solutions, it introduces a set of new problems as well. Glycol is harder to pump than water, so you'll want to have plenty of capacity. It also foams, so getting rid of micro-bubbles means an air separator is needed if glycol is being used. I used it at my old place in the floor, but am not at the new one. If my floor gets to the freezing point, I'm in bad shape on every possible level, since all my water comes into the building in the garage.

Electric is 100% efficient-- every kW/hr you put into the water yields 3412.14 btu/hr of heat at 100% efficiency for all practical purposes. The problem is cost. Most of us are paying about a dime per kW/hr. 1 cubic ft of natural gas has about 1020 btu/hr of heat capability, so at 70% efficiency (a standard water heater), you'd need 4 cubic ft of gas to equal about 1 kW/hr of electricity. The cost of the gas in my part of the world is a fraction of the electricity. If you're OK with the money, or have no choice-- an electric water heater would work fine, as long as the capacity equals the load on the floor. Recovery time for electric heat is generally slower, but with in-floor heat, it doesn't matter. The slab is a huge heat-sink, and one you warm it up, you'll want to keep it warm.

A "perfect system" is one whereby you heat the room primarily with the in-floor heat, up to a "set-back" temp (50-55*), then have a forced air system (furnace or unit heater) for occupied periods. I'm doing this in the new place, but it's equipment intensive. Either the in-floor, or the furnace would have the capacity to heat the space, but I've got both, so that I can have a nice warm floor, hold the temp at 55*, and bump it up quickly. In reality, I'll probably never use the forced air, but since I wanted A/C as well, I just put in a high-efficiency furnace with an A/C coil instead of an air-handling unit with no heating capability. It's definitely a buy once/cry once situation, as long as it works.

So, you see-- when I say I'm building an entire house around my desire for a nice garage, I really mean it. In the midwest, a nice garage is more about being climate controlled than raw space, although space is a nice thing to have.

Thanks for the info Stan, I have styrofoam under the slab already but the sides are exposed so I would have to wrap styrofoam around all edges of the slab I would think... I will have to think about how to get NG to the slab as in Ontario we lead the country with electric prices I think their goal is to reach the sky mimiking lighting heights. 

@IaM-Ray,

You're good without wrapping the sides, although that'd be great. 

@Stan Galat 

I was thinking about the floor heating in my garage again.  

I do have a radiant heat set up in my house with a 40 gallons tank (pilot light) that heats the basement family room floor and runs also one small rad.  I have some reserve left and I was thinking of running another zone from the system and making it run outside in a conduit fully insulated in styrofoam and of course with a heating wire as well and extra pex and a chord to make sure we have spares in case of problems and we can even pull another pex feed should the chord be needed.

 Since it is about 8-15 feet from the house to the inside of the garage I was thinking that a sufficient size pump should be able to handle the length of the travel and back from the garage and heat the garage floor if I repoured a 2&1/2 inch layer of real cement on top of the existing floor by using tapcon screws and the pex tubing. 

Any thoughts on this one Stanley...?

Ray

IaM-Ray posted:

@Stan Galat 

I was thinking about the floor heating in my garage again.  

I do have a radiant heat set up in my house with a 40 gallons tank (pilot light) that heats the basement family room floor and runs also one small rad.  I have some reserve left and I was thinking of running another zone from the system and making it run outside in a conduit fully insulated in styrofoam and of course with a heating wire as well and extra pex and a chord to make sure we have spares in case of problems and we can even pull another pex feed should the chord be needed.

 Since it is about 8-15 feet from the house to the inside of the garage I was thinking that a sufficient size pump should be able to handle the length of the travel and back from the garage and heat the garage floor if I repoured a 2&1/2 inch layer of real cement on top of the existing floor by using tapcon screws and the pex tubing. 

Any thoughts on this one Stanley...?

Ray

I don't remember your garage set-up but I can't imagine how much that pump would be working to heat a cold cement garage floor in a "relatively" uninsulated garage. ANY garage door makes it relatively uninsulated imo

So, here's the thing:

If you run the loop outside, you'll need to run glycol. If you ever lost power, your pumps would stop, and your heat tracer would die. In Canada, it wouldn't take long for the pipe to freeze, unless you're burying it below the frost-line. Even then, I'd be worried about bursting the PEX below the floor. Glycol in an outbuilding is a non-negotiable for me.

If you run glycol, micro-bubbles in the system can become a problem, unless the loop is very simple (yours sounds like it isn't). If you don't have an air-separator, you'd need one. The greater the solution of glycol, the more your pump performance decreases. As I said, I had glycol in my new house loop, but the pumps weren't pushing adequately and I had to either go to bigger pumps or go back to water. I went back to water for now.

I think in your application, I'd personally just look at a separate system for the garage. Getting gas to the garage is going to be cheaper and easier than getting glycol out there. It might even be an idea worth considering for others with cheaper power or a more temperate climate might be to use a small electric water heater, depending on how much power costs in your part of the world. Point of use electric water heaters are not that expensive, and the amount of glycol in the system is greatly reduced once the tank is gone. 

The best alternative might be to just put some exterior plywood on the floor to take the chill off, put some nice rubber garage tiles on it, and install a nice gas-fired unit heater (Modine Hot Dawg or equal from any one of several manufacturers). The floor would not be bad to work on, and the cost would be a fraction of any of the other alternatives.

Of course, these are just suggestions. Your mileage may vary. I wish you blessing in your endeavor. 

Total aside:

The @Stan Galat thing didn't notify me via email. I even looked in the spam filter. Strange.

I've tried that on my own username a few times - nothing.

If either have changed your email since you signed up with the SOC then you will not get any notifications.

@Stan Galat

@Gordon Nichols

I checked. I haven't.

What is mentioned here about putting wood or vinyl tiles on the floor brings up an interesting point.  Absent any heat input, the wood or tile or concrete at any given time will all be the same temp, and in winter that would be cold.  The concrete has very high thermal conductivity, so any heat applied, say from a space heater via the air, or lets say your backside, lying down to adjust the valves, is going to conduct from the source (you) into the concrete pretty fast, and the concrete is not going to heat up much.  The concrete also has high heat capacity (specific heat times density), which means it can hold a certain amount of heat and not gain very much temperature -- it just stays cool.  So it will feel cold at first, and stay cold for a long while.  Adding a less conductive layer with low heat capacity  t means that at first, the surface will feel cold, but as your heat goes into the material's surface, it can't flow out so readily plus has low specific heat, so heats up rather more quickly.  And so the surface becomes warm, and you don't feel so cold. About the best thing here would be styrofoam, w very low conductivity and low heat capacity, and this would feel warm almost instantly once you lay down on it.  This is why walking barefoot on a concrete floor feels cool (rapid heat loss out of your foot), walking on wood floor is better (less rapid heat loss out of your foot), and walking on a rug with very low conductivity and low heat capacity feels nice, and this is so even though all surfaces are at the same temperature just before your foot lands.

ANd the part about insulating a concrete slab: this would be especially important around the edges if they are exposed to the outside.  Insulating between ground and slab on the bottom will also help, but the ground tends to be lesscold than the outside during winter around here, somewhere in the 50s I think, and remains that way pretty much year round.  Even so, one could easily insulate between ground and concrete to, and that would be all to the good.

So for a part-time garage, and limited budgets, I'd be thinking about heating the air on demand, using electricity directly, or possibly a heat pump.  Or a gas fired air heater if that is convenient.  I'd insulate the concrete edge from the outside (2" rigid styrofoam min), and think about one of those vinyl tile applications to put on the floor. Maybe these can be applied with some sort of rigid insulation underlayment. Which is not to say I would not thoroughly enjoy an electric or hot water grid in the concrete, which would be the cat's pajamas if one was building new and had the money to spend.  Speaking of money to spend, how about this garage:

Thanks for the input. My garage is 24x24 feet and has a loft accesible by a full stair case for storage. 

I have two insulated garage doors for what that is worth and a slab poured over 2inch of styrofoam... I should have included floor heating PEX at the time but hey you know how life it ... 

So today it is 10 degrees and goes to ZERO Fahrenheit at times and even down to -22 fahrenheit on a cold snap. 

At present I have a infrared small heater that does 500sq ft which is pretty much keeping it at 60- ish but It can't keep up on the real cold snaps. 

I was thinking that encasing the tubes in a cube of 8 inch styrofoam might allow the water to be protected so long as we have battery backup and a heating cable.  But I guess if it does completely stop we would be in trouble. 

I think my cost to run a gaz line would probably in the 3K area just to get it to the garage as it is on the otherside of my house and the whole yard is terraced and interlocked so that is why I was looking to use the existing water system. 

I will have to give some thought on a very small water tank that would be able to push Evans coolant or Propylene Glycol for heating.  I think a heavier duty pump might be called for.  I have seen open systems on the WEB which gives me a few ideas on how to remove bubbles in the system. 

More thinking needed for now ... it might hurt ...

I've wondered for a while why (or if) no one has adapted any of the snowmelt or bath tile radiant systems to a garage. Seems to me the most obvious move: $1,000 in tiles @$1/sf, plus this electrical junk (another $1,000 or so) & a few bags of thinset would get it: $2500 or so plus a weekend or two of great enjoyment.

It's not cheap heat but could not be beat for utility--no flames, no air circulation blowing dust into your new paint job... 

Thoughts?

And another thing: can anyone explain why the same tech that gives us heated seats & electric blankets could not or should not be adapted to a garage floor mat system? Seems like you could make them so they interlock with electric connectors, and just specify a max number of tiles per circuit. Then it'd be down to running a few wires.

I figure these both must be terrible ideas or else they'd be all over the market. But why?

"Point of use electric water heaters are not that expensive, and the amount of glycol in the system is greatly reduced once the tank is gone"  

Stan this point you made regarding point of use... did you mean a tankless water heater or a small hot water tank like they do to simply wash hands in an office something that fits in the drop ceiling.   I have checked using a tankless heater before and some could and some could not be used. 

El Frazoo that garage pict is awesome but I think the guy lives in the south

IaM-Ray posted:

Stan this point you made regarding point of use... did you mean a tankless water heater or a small hot water tank like they do to simply wash hands in an office something that fits in the drop ceiling.   I have checked using a tankless heater before and some could and some could not be used. 

Yes, a  tankless heater. Regarding if they can be used: they can all be used. Your 40 gal gas water heater is not rated to be a heating appliance, but it works just fine.

edsnova posted:

I've wondered for a while why (or if) no one has adapted any of the snowmelt or bath tile radiant systems to a garage. Seems to me the most obvious move: $1,000 in tiles @$1/sf, plus this electrical junk (another $1,000 or so) & a few bags of thinset would get it: $2500 or so plus a weekend or two of great enjoyment.

It's not cheap heat but could not be beat for utility--no flames, no air circulation blowing dust into your new paint job... 

Thoughts?

 

I had a paragraph about warm-tiles in my original response, but I looked back on the thread where Ray had talked about the cost of power in Ontario and deleted it. In a place without gas or down south, I'd think it'd be an acceptable alternative for a retrofit.

I had them, though, in a bathroom at the old place. Here's what I can say-- paying way-too-much to the electrical co-op we were getting power from (.14/KwHr?), it cost about $20/mo to heat the tiles in a master bath. Heating a 575 sq ft garage would be really, really spendy.

Passive heat (without air movement) is going to be best. Personally, I'm not a fan of heat-pipes (overhead infrared heat) for a variety of reasons, but first and foremost they do almost nothing to make the space more comfortable. The heat is on the top of your head (which is almost never cold) not on your feet which always are. The other thing? They're like a heat-pump-- they should be excellent in theory, but nobody that has one ever likes them.

In general, my list above is still what I believe: a fire of some sort is always preferable to any other alternative-- but if one has a flame in the garage, it needs to be vented outside at a minimum, and in a sealed combustion chamber (outdoor air for the burner) in an ideal world. My water heaters (boiler and domestic HW) are in the garage, but they are 90%+ condensing equipment, which uses outdoor air for combustion. I've got a furnace as well (mostly because I wanted A/C out there, and a furnace is as cheap for me as an air-handler), and it's 90%+ condensing as well. 

Just got a recent home hydro bill. All in...taxes and robbery for delivery...23.32 cents per kwh. And the crazy part is, is that Ontario has a surplus of electricity and frequently PAYS New York State electricity dealers to take their surplus juice. Yes...there not giving the stuff away, they'll pay you to take it. 

We're still miles ahead by heating our home with ground source geothermal though. 

"Fine Homebuilding" is the mag the picture of the fru-fru garage came from. Great rag; love to read it cover to cover when it comes.

And, From Ed:  "They're like a heat-pump-- they should be excellent in theory, but nobody that has one ever likes them."  Well, yes and no.  Electric heat pumps started out not so great 20 or more years ago.  But things have changed a lot in the intervening years.  Efficiency for household systems is very good these days (like fleet mileage for cars, these numbers are "mandated" by gov't regs -- must be above a certain SEER or you can't sell it.) , air handling in smarter, T-stats are smarter, and the whole thing is, on balance, reasonable.  All I have is electricity here at my ranch, so electric heat pump is the way I get heat and A/C.  Initial system was pretty poor, always cold and drafty in winter, but newer system is much better. Same deal at the vacation house at the beach, and the newer unit there made a really big difference in cooling bills after install vs the original.  And I do have a wood stove in the family room, so I cheat.  and man have been needing that the last few days.  Was down to 11 last night and single digits expected tonight.  This is Stroud weather, and he can have it.

I'm looking to build a garage, and am leaning toward having the slab well insulated, and will use one of those "split" heat pumps, which would give A/C in the summer too.

Here I started a thread with a zero foot print idea - plus actually recycling those 16 oz Schlitz beer cans into something useful. It got twisted into an Al Gore energy hungry monster.  My next idea was to use that methane gas from drinking all that "Schlitz" beer (it used to have a shorter 4 letter name) - but I will refrain.

Freezing this am (wind from the cold North) but whoo-hoo 74 by Wednesday.   

So the bottom line for radiant, whether thinset permanently or inside vinyl or rubber floor mats, is that kilowatts are too expensive. Seems right. Electric heat would look to be about 4x the cost per hour of gas here in Maryland. Something like $2.20 per hour. 

That's for my 1,000-odd square feet under a 9-foot ceiling. 

Today it was 14F when I got up, and the thermometer I left in the corner of the garage nearest the house said 38. I put it in the back bay where I keep the lift and Bridget, and an hour later it was at 32. Apparently, my garage holds a decent amount of the heat the house bleeds into it. And I know my windows are total crap. Once I velcro some polycarbonate over them I should be better yet.

So.

Realistically-speaking, I only need to come up 30 degrees or so. The 50,000 btu Mr. Heater Big Max I been coveting is way more than enough for that, and with gas at about 85 cents per therm I'd be paying about 54 cents per hour to heat the space 50 degrees from zero. And I just today figured a new thing out, which is that a couple of the unused 4-foot electric baseboard heaters that I've been meaning to remove from the bedrooms upstairs (long story about the home's P.O. there, don't ask) could be installed in that far bay easy enough. All I'd have to do is run a couple 12/3s from the main panel to them for 220/240. et voila! Easy (albeit expensive at about $1 per hour) provisional heat in that bay with no chance of fans blowing dust into new paint or dust reacting with open flame....

Belt & suspenders, call it.

There are fewer than 20 weekends a year when I would possibly need substantial heat in this garage. Mid-November through mid-April, say. Probably 10 at most when the outside temps are likely to be low enough to get the garage interior anything close to freezing (January through mid-March). At $11 per weekend (all gas x 10 hours x two days) we're looking at $110 a season for a roasty-toasty workshop. 

And that's assuming I'm out there all weekend, every weekend, when it's cold. Which ain't gonna probly happen.

This job is officially overdue.

El Frazoo posted:

 

.  This is Stroud weather, and he can have it.

 

Got no choice, Amigo. -24C tonight.  We watched a couple of re runs of Deadwood with a few logs on the fire and a good merlot. 

I was born in Churchill, Manitoba so that makes me a bit loopy anyway.... :-)....Not that I had a choice mind....but some were worried about the Russians coming over the top. 

I do remember being there later and the Yanks had quite an Army presence up there too. A fine group of fellas in all but not many hockey players. Some of them were from parts down South though and with a darker complexion than some, they really stood out in those "bunny suits". Their eyes had a ....."worried" look about them in January.  :-) 

I'm fascinated by ancient Roman architecture - England (Bath) and Germany (Saarbreuken) have great examples of radiant heated floor with great mosaic tiles to boot!

Seen the remains of a few of those in Israel... Beit Shean is an awesome dig... 

http://www.attractions-in-isra...shean-national-park-–-tel-bet-shean-in-the-jordan-valley/

Re: Heat Pumps: David's geothermal system gets a pass from all my observations regarding heat-pumps. If you can swing the cost of entry, it's a good idea (I've got a long story about that, but it'll be some other time), assuming you have some kind of long-term warranty.

For the rest of the world-- I can offer the same kind of anecdotal observations as Kelly, with a different spin. We presently live in a new apartment building while we are building the new place. The apartment is all electric, with an air-to-air heat pump. I'll agree to disagree with El Frazoo-- the heat blowing from the registers is barely warm, and I find it hideous. There's nothing pleasant about 85-90* air blowing around. It's 10* outside right now, and there just isn't that much heat to pull out of the big world.

I appreciate Ed's approach to most stuff, and figuring it out before hand is a good idea. Here's what I will say: if I were spending money to make a cod garage into a usable shop, I'd start with insulation. Lots and lots of insulation. I'm not talking about cellulose, vermiculite, or fiberglass-- I'm talking about sprayed in open-cell foam. Once you try it, you'll never go back to not having it. It's about R7/inch, but the big value is in how it stops air infiltration. An inch of foam and some R15 in the walls, and an inch and a bunch of cellulose in the ceiling, and you'll be able to heat that shop with a light-bulb, Ed. It's the gift that keeps giving.

When we started talking about this, I mentioned (or at least I think I did) a wood-burner, and I still think this is a good idea for when you are in the shop. The heat there is passive (no fans) and intense and pleasurable. A small garage wouldn't take more than something tiny, and you could use scrap lumber from construction sites in the new neighborhoods (believe me, the owners and contractors would be glad for someplace to get rid of some scraps besides the dumpster). Use the baseboard resistance heat for "unoccupied heat", and fire up the wood-stove for heat while you work. I guarantee you'll be happy to lay on a concrete floor if you've got one of those babies rolling coal. 

Wolfgang continues to amaze with a really complete picture for nearly everything, and yes-- those Romans were pretty smart (heated floors AND walls).  

Thanks for that, Stan. The cost for entry for me was a joke. The Fed and Provincial experts had a deal whereby they'd rebate big bucks if the install was on a home over two years old. Yeah.... and we pay taxes for experts like that. 

Anyway we built our house with me as the general contractor and things went very well. I only fired one contractor and that was the plumber. The lazy bugger never showed up at planned meetings on site with the HVAC and electrician guys.

Long story short, I got five estimates around $20 K each to install ground source heat. Five quotes might seem excessive but I'm new to the game and for me it's big bucks.  One said 4 ton, three said 5 ton and one said 6 ton and he'd like to adjust one heat run that he thought didn't meet his plan. I knew a lad with an excavator nearby sitting idle and got him cheap on site. The deal was struck with the latter at 6 ton and we coordinated things very well. My total cost was $22K and Gov gave me $15K back. Can't loose on that.

Here's the kicker. The heat system / ( cooling system too) works very well. It will heat our house on it's own strength until three consecutive nights of minus 28C, then it will try to kick in the aux electric heat unit. I keep that unit disabled and put on a few more logs on the fire and our open concept / ceiling fan situation running the job gets  done. If I had chosen the contractor with a 4 ton unit, I'd be screwed...totally inadequate. The five ton choice would be quite marginal. The six seems ideal and I'd bet if I had chosen the four or five ton unit and had lousy performance, ther'd be little chance for remedial satisfaction. 

Good stuff, David. Yours is state of the art.

Stan: My garage has a foot or more of fiberglass up above the ceiling, 3.5 R-15 in the walls between the studs, and that hard stuff at 1.5 inches ( I think R9?) on the doors. Not bad!

Def needs some Great Stuff along the floor-to-wall joints though, and maybe some more up high. Plus the windows need to be sealed.

I do have a 6-inch or eight-inch chimney installed. The PO apparently had a little wood stove working in there. I never considered duplicating that, since it would sit in the middle of one of the bays and be something of a nuisance when moving things through the garage from the front of the house to the back yard—something we've done a lot in recent years.

But still. I could probably buy a decent old iron pot-belly or a barrel stove for a couple hundred bucks and have it up and running on any given Saturday. Like right-the-flock now. Definitely food for thought.

.....old iron pot-belly or a barrel stove ( or combustible furnace) in a shop where you do glass and or any type of paint work is not a good thing. Many years back in NJ we ran a shop furnace to get the shop temp up and someone ( not I)  was suppose to shut it down completely, we wet the floor down,  primer and the first base coat applied then the furnace decided to come on with a muffled boom........the air in the shop became instantly clear we....were,  lucky.

Yes, will agree whole heartedly: you cannot have too much insulation.  And cutting down on infiltration is the exact right thing to do. Built my house that way. Trouble w/ the garage and on-demand heating concept (vs. just keeping it warm all the time, whether in there or not) is the good insulation will allow you to get warm air in a hurry and w/ not too much expense, but that damn thermal mass called concrete floor is going to be cold for a L O N G time.  So, just throw a blanket down where you need to lie down, and maybe that will suffice.

I suppose a lot of shade tree mechanics run pot belly stoves in their garages in the winter when their leafy shade trees are not so much, and the ground is frozen outside.  But I just can't see putting fire in the place where I store (and might now and then spill) gasoline.  Just sayin' . . .

Hyperbole aside, any open flame is going to present the same challenges. A wood-stove is not so very different from a standing-pilot water heater or a non-condensing furnace or unit heater. All of these are quite different than a ventless heater, in that the noxious stuff is going up the chimney or flue. All of the vented gas-fired stuff is approved for use in a garage.

A condensing (sealed combustion chamber) heating device (tankless water heater or 90% furnace) is the best way to go, but I've heated many work-spaces with gas-fired heaters, without ill-effect. Go into almost any commercial shop in America, and you'll find non-condensing gas-fired heating appliances, vented outside the building.

That's what I had in my shop when I built Pearl - an old, oil-fired, forced hot air furnace, vented to the outside through a power vent™ because I didn't want to put in a full chimney.  I think it was about 125,000 BTU and it just sat in a corner and made lots of heat.   I got it from the want-ads and a neighborhood heating guy installed it for me.   No idea about efficiency (maybe 80% in those days) but it wasn't used all the time, just when I was out there and the rest of the time in Winter it sat at 55 degrees.  Maybe went through a tank of oil every two years.  Worked great.

As to the Roman design, I like the concept, but what about smoke and creosote?  Seems to me that would be a BIG problem after a while.  And of course you'd have to build the entire structure out of stone.  Oh boy.  And where would all that wood come from??  Hmmm . . . I think I know why they had so many slaves.

El Frazzled one wrote:  "As to the Roman design, I like the concept, but what about smoke and creosote?  Seems to me that would be a BIG problem after a while.  And of course you'd have to build the entire structure out of stone.  Oh boy.  And where would all that wood come from??"

Tuscany, I suppose............

We should go over there and check it out.  I always wanted to eat my way across Tuscany.

https://www.madabouttuscany.co...Z5UJAArgoaAte_8P8HAQ

Me too.  Have given it brief gos a couple of times.  That section of the world never disappoints.

And now for something completely different:

!!! Is that wood siding?  Gonna bake right off.  Won't last five years.