Maximizing Heat Generation From Kerosene Heaters

Now that I’ve got the space envelope dealt with via isolation and insulation — i.e. keeping the outside out and the inside in, a concept I invented  — let me turn to how I deal with the third point of the triangle, namely generating heat.  As a facilities designer once told me, “If your envelope is tight enough you can heat the space with a light bulb.”  Well, mine isn’t, and besides, in the Age of the Nanny State incandescent bulbs are apparently part of some crazy scam having to do with Gaia Apocalypse.  You just can’t make this stuff up sometimes.

Anyhow, I had long been skeptical, at best, about kerosene heaters in a tightly enclosed space.  After talking to my friend Dennis, whose hardware store I have patronized since the days when his dad was in charge, I decided to take a chance and give it a try.  They do have the distinct advantage of being relatively inexpensive to purchase, especially if you buy them in late March like I did, and before the current anti-energy regime in Mordor on the Potomac they were cheap to run (this witless cabal promised to raise fuel prices to the moon, and they did their best to keep that promise!).  But I was concerned about the stench of them in a closed shop, and their ultimate safety from fire and toxic fumes.

As I have learned in the past months these concerns, while not irrelevant, are not of the level I had thought.

Regarding the odor of the kerosene heaters, I learned that all kerosenes are not alike.  Some are stinkier than others, and even if they are K-1, I can tell the difference between local kerosenes.  I naturally purchase mine from the better supplier.   Second, it is really important to keep a clean wick in the burner.  If you notice the smell of burning kerosene when you first come into a heated space, you need to think seriously about swapping the old wick for a new one.  I plan to make it a routine to swap out mine at the end of the winter every year.  And third, I make sure not to hit the “Off” lever on my heater until after I take it out into the unheated (and better ventilated) part of the barn.  This is because the wick is on a spring loaded rack, and it snaps off in an instant when you hit “Off.”  This means that the hot wick frame will volatilize some of the kerosene on the wick and introduce a tiny bit of the kerosene vapor into the air.  It’s not a hazard, but it does stink.

As for fire risks, they seem to be pretty small as almost all modern kerosene heaters have automatic cut-offs when the units are jostled hard or even if they were knocked over.

In use I employ a few enhancements for my heater which in my observation increases dramatically it utility and efficiency.  These allow a single 18,000 BTU heater to keep a 3000 cubic foot space comfortably usable, but not quite to the level of cozy.

First, I removed the carrying handle from the unit and placed it instead on its own rolling cart, complete with a handle made from hardware store pipe.  This allows me to move the heater without having to pick it up or handle it directly.  Second, and perhaps the most important thing, I placed a couple of fire bricks directly on top of the combustion chamber.  The bricks heat up and then radiate the heat into the space rather than working solely by convection.  I feel that this increases dramatically the efficiency of the heater.  Yes I know it does not “create” more BTUs, it just captures them and distributes them differently, and in my experience, better.

I add even more thermal mass with an octagonal shelf of 1/4″ aluminum diamond plate resting on the top grill.  This not only increases the heated mass and thus the radiant heat distribution, but it beneficially disrupts the convection coming up through the combustion chamber and distributes it more widely by diverting the hot air around the shelf, pushing it out into the room.  Besides, it’s nice to have a warm shelf for the glue pot to sit on, and sometimes my tea kettle for tea (or hot chocolate if Mrs. Barn isn’t watching).

So, how well does it work?  I think pretty darned well.  There are times when I am only in the shop for a while, or first thing in the day before the cast iron stove gets cranking, and the kerosene heater raises the temperature in the shop 15, 20, or even 25 degrees.  That is not bad.  I find that in the dead of winter I use about 1/10 of a gallon of fuel per hour with the kerosene heater, which for me works out to about $20/week.  From where I sit, making a cold shop usable space for $20/week is a great deal.

My final concern was health, but once I thought about it I realized that the primary byproducts of kerosene combustion are soot and water vapor.  I don’t mind the water vapor at all, and as long as I use premium kerosene and have a clean wick, it’s not a problem.  Still, I keep a carbon monoxide monitor hanging on the wall a few feet away, generally a good idea whenever you are using open-combustion heat source in an interior space.

In short, I am exceedingly pleased with how my kerosene heaters perform (I actually have two, but only use one in the studio with the other out in the main barn space for whenever I need localized heat for something).  I’m even thinking of getting a much smaller one to keep in the bathroom which isn’t heated, the use of the unheated bathroom bringing back memories of using the open air privy in the dead of winter when my dad was pastoring a tiny country church in Minnesota.  Now THAT was cold!

Up next, supercharging my cast iron stove.

PS  As I head up the hill to the barn, it is snowing sideways.  Literally sideways.  We are expecting several inches of snow and 50 mph winds today.  It is good to have heat!