A Wood Stove — Getting That Warm Feeling

We love wood heat. We’ve had wood stoves for most of the last twenty years, in four different houses. The mobile home we live in now is old and leaky, and takes two or three electric space heaters running most of the time on cold nights here in Middle Tennessee to keep it in the low 60s, if the outside temp drops much below 40. Fortunately, we are comfortable in the low 60s.

BREAK FOR IMPORTANT DISCLOSURE:

I am NOT a professional wood stove installer, a lawyer, a fire inspector, an insurance underwriter or any other kind of wood heat expert – just a smart-ass blogger. This is not, no way, no how, presented as a how-to or a recommendation on the following project; rather, it is simply an account of the way I did what I did, and is presented for entertainment purposes only. Got that? Entertainment. Okay, then.

This article will not cure cancer, shrink hemorrhoids with or without surgery, will not get you out of filing income taxes, and it will not make you more attractive to the opposite (or the same) sex, or make you smarter. Well, maybe you’ll get smarter, but no guarantees. As to the rest, forget it. Ain’t happenin’. Just read on, and enjoy it.

I’m glad we had this talk.

END OF DISCLOSURE

Trailers are apparently not supposed to have wood stoves in them, according to The Powers That Be. At least, they are not supposed to have stoves we can afford. We were able to afford a Vogelzang Frontiersman,

Vogelsang Frontiersman

especially after it went on sale last spring.

I thought we could install this stove in such a way as to avoid the hazards inherent in a trailer install, and I went about it with that in mind.

This is a little stove, and one of the few small enough that it would not continuously overheat our small living space (it is specified for “up to 1,000 square feet”).  The instructions that came with it explicitly state in several places that it is not to be installed in mobile homes. Of course, we installed it in a mobile home.

The rationale for the prohibition is apparently twofold: The stoves that are OK to put in a mobile provide for getting their combustion air from outdoors, via a discrete duct and connection between the outdoors and the firebox. Those stoves are all pretty pricey; certainly a lot more expensive than ours.

The Frontiersman has no such provision, but our mobile has plenty of infiltration leaks, including forced-air heat ductwork that is uninsulated, cracked and separated in several places. I have plugged many of the heating vents, but not all, and I still can feel cool air leaking up from most of them. This is definitely not one of those airtight, super-insulated mobiles from the last few years.

It’s a bit more “vintage,” than that. It also has inadequate windows, some of which are cracked or broken, and all of which need to be replaced. They are another source of fresh air, whether we want it or not. I’m not too worried about using up my oxygen, in other words.

The other concern is that this mobile would burn like a cardboard box if a heat source got close enough to a wall. Well, that’s certainly a reasonable concern, and one I share.

To reduce our odds of becoming flaming human sacrifices to the gods of global warming, we put the stove on a ceramic tile floor. In the spirit of over-engineering with which I approach most projects, I put a layer of ¼-inch cement board down over the existing ceramic tiles, and cemented and grouted in another layer of ceramic tiles over that. I covered an area much larger than the one specified in the instructions that came with the stove, as well. A sandwich of ceramic tiles around cement board seemed reasonable to keep heat from the bottom of the stove away from the sub-floor. Ceramic tile is obviously resistant to fire, and “cement board” is fiber-reinforced concrete, with high flame-resistance characteristics and good insulation.

Stove platform detail -- existing tile, below, cement board (not visible), new tile on top

Platform covers more floor area than required; also serves as entryway

To keep the walls of our live-in cardboard box from burning, I put over-engineered, home-built heat shields on the wall behind the stove, and between the stove and the living room where any furniture might go. The rear heat shield consists of a layer of Hardiboard cement board, same as the platform, up more than four feet from the floor, completely covering the existing wall, and a sheet of roofing metal mounted on galvanized steel, “Unistrut” channels, and four vertical runs of ¾” metal conduit.

The sheet metal screws into the conduit, and the conduit is clamped against the Unistrut. The cement-board-covered wall surface is separated from the sheet metal by about a 3 & ¾-inch air space. The upper and side edges of the shield are supported with galvanized steel angle with two-inch legs, about 1/8-inch thick. The steel hardware between the sheet metal and the cement-board-covered wall is intended to be massive enough to dissipate heat from the sheet metal that might otherwise be conducted to the wall.

The Unistrut and two-inch angle were surplus, salvaged from an old antenna tower. The roofing sheet metal was a gift from our nephew, who had it left over from a chicken house project.

Cement board (L), air space (C) and sheet metal (R)

Unistrut detail, rear heat shield

The heat shield between the stove and the living room space is another piece of roofing metal, bolted to cement board, and supported by more, 2-inch angle.

Side heat shield, inner view

Side heat shield, outer view

Both heat shields, early in installation

This morning I over-fired the stove, in the process of learning its preferences, and the stove top got to just above 500 degrees F, which is hotter than it needs to be, but (based on experience with previous woodburners), is not dangerously high. I closed the damper completely, and watched the stove for about two hours. The stove and stove pipe never got hot enough to glow, even in low light, but I kept the fire extinguisher and cell phone handy, being something of a pessimist. The curing stove paint and chimney sealant set off the smoke detector a few times, which is a normal part of stove burn-in. Otherwise, it was a non-event. The stove soon cooled back into the efficient operating range, according to the thermometer.

At the peak of the heat, the sheet metal on the side shield was just a little too hot to touch; on the opposite side, the cement board was just warm. The rear shield, which has the air gap behind it, stayed cool enough to touch throughout, and the cement board on the wall behind it was only slightly warm. The drywall above the heat shield was slightly cool. As I said, the stove temperature dropped back into the normal operating range in about 45 minutes, and stayed there for about two hours, warming the place up enough I had to open a window and a door.

The connection between the stove and the world is single-wall chimney pipe from the top of the stove to the wall, where it connects to a Simpson Dura Plus through-the-wall chimney kit.

The Simpson kit is a very conservative design, consisting of triple-wall pipe, and a thimble (the transition from the single-wall to triple wall, and also the means of penetrating a wall made from flammable materials safely) that offers a lot of thermal isolation between the stack and the wall materials.

The inner wall of this pipe is stainless steel. It is wrapped in high-temperature insulation, and another layer of sheet metal, surrounded by an air space and another wall of pipe. The piece of this pipe that passes the exhaust through the wall thimble is 9 inches long. There is no, single-wall pipe inside the wall. It stops at the inside portion of the thimble, seen below. The single-wall pipe comes from the stove on the left, and seals and is screwed into the transition piece from the kit. From there, it connects to the triple-wall section, and then to the tee, seen in the exterior shot. By the way, the sealant around the outside of the thimble is high-temperature silicone caulk, made for this purpose by Rutland.

Inside portion of "thimble," showing sealing materials

The black material at the joints between the single-wall tubing sections, and between the tubing and thimble, is Rutland stove cement.

It is applied inside and out at each joint, and along the seams of the tubing.

Simpson tee connector, on outside wall. Note un-melted snow in braces and base

This connects outside to a “tee” section (above) that, like all the chimney parts from here up to the storm cap, is also triple-wall. This is an important part of a kit by Simpson made for putting a chimney through a structural wall safely. What would be the vertical leg of the tee, if it were oriented upright, connects to the through-the-wall segment. At the end of the downward-facing (as installed, now, not as a letter “T”) end of the tee is a stainless steel cap, which is secured with screws. This acts as a cleanout access, since there is a straight shot up the tee to the storm cap from there. A piece of galvanized sheet slides into the bottom of the tee support, and serves as a barrier between this cap and anything flammable enough to be a concern if it came into direct contact with the cap. The flange of this sheet is visible at the bottom of the tee assembly in the picture. A chimney brush on ten feet of Fiberglass rod sections will reach all the way to the storm cap from ground level, eliminating the need for a scary, vaudeville ladder act.

The triple-wall chimney keeps the exhaust hot all the way to the top, reducing the condensation that becomes creosote, and also provides maximum draft, which improves the efficiency of the stove.

The triple-wall actually penetrates the building wall, and it passes through the thimble, which provides more layers of sheet metal and air gap between the hot exhaust gases and the wall materials. A note on the picture of the tee installed: The snow seen at the bottom of the tee support – un-melted by running the stove for twelve hours or so — is a good indicator of how effective the insulation is in the triple-wall kit. If it won’t melt snow that close to the exhaust, it probably won’t set the wall on fire.

Triple-wall chimney, standing proudly

The triple-wall stack, seen above, consists of three, 36-inch sections atop the 12-inch leg of the Tee. These sections, by the way, use a “bayonet-style” connection that twist-locks in place, tightly mating all three walls, the insulation and the air space without needing sealant.

I did not trust the screw-in connections of the tee and lower mounting bracket to hold the stress imposed on it when the wind blows on the chimney. Not that the brackets didn’t look to be up to the job, but I wasn’t sure the wall would hold the lag bolts I used to fasten the lower supports. I used the second (also included in the kit) bracket as an anchor point for the guys seen above. Sloping toward the camera, into the lower, right-hand corner of the picture, is a section of ¾-inch electrical conduit, of the same type I used on the rear, interior heat shield.

The other end of the conduit is clamped to a piece of steel angle which is bolted to a porch rafter. This serves as a “dead-man” guy, since it is rigid, and would tend to prevent the chimney from tilting toward or away from the wall. The wire guys are galvanized guy wire that is plastic-coated, and threaded through the holes drilled in the bracket for screws. The wire guys are a little slack, because pulling them tight would only increase the stress downward on the chimney pipe, without a useful increase in support to either side.

Rigid, "dead-man" guy, clamped to porch roof at right

Storm cap/spark arrestor

Between the dead-man and the wires, the chimney is supported in four directions. Sure, a strong-enough wind would still blow the chimney over, but a strong-enough wind would blow the trailer over, too. That’s just a fact of life in tornado country, and I can live with it. My objective was to make the chimney reasonably secure in most conditions.

You will have noticed the top of this stack has a cap, called a storm cap. It keeps rain from falling directly into the chimney, and a wire screen around the opening is supposed to keep burning cinders large enough to start a fire from getting out, as well as birds and other creatures from getting in. This is not a frill or an optional accessory, and it is included in the kit. Like the Dura-Plus sections, it uses a twist-lock means of attachment.

Carbon Monoxide detector -- cheap protection against a silent killer

Besides the wood stove accessories I’ve already mentioned or shown in photos – fireplace tools, fire extinguishers, etc. — there is another one, and it is required: a Carbon Monoxide (CO) detector. A subtle defect in the stove or chimney could let CO leak into the living space, which could be deadly. This detector is inexpensive, and runs on batteries, which is important, since one of the times when such a stove would get the heaviest use is during a cold-weather power outage. Along with smoke detectors and fire extinguishers, no wood stove install is complete without at least one CO detector. CO is odorless, invisible, silent and an insidious threat. Don’t leave yourself, your family or your pets exposed to that risk.

The point of this article is to relate my adventure in wood stove installation. I hope you have been entertained, but have resisted the impulse to be informed, per the “IMPORTANT DISCLOSURE,” above. Should you undertake to install a wood stove in your death trap of a mobile home (and I’m not recommending that! God forbid!), I hope you will do it safely, and that you will experience the same “warm feeling” I have.

May you know that, even if Mom Nature and Uncle Sam get in the way of furnishing the outside sources of energy that keep you warm in good times, you will have the means to do it for yourself. Safely!

The Woodstove Channel -- My favorite program!

Tags: DIY, Environmentalism, heating with wood, mobile home, off the grid, off-grid, self-sufficiency, trailer, wood heat, woodstove