Revisiting the Wood Stove

The old is new again

I grew up in a house that was heated by a wood stove. After many years of racketing around in strange places where wood was not a common fuel, we are building a modern home in which a wood stove will once again be the major source of heat.

This Dutchwest noncatalytic wood stove may look like one of the old cast iron stoves, but a lot of technology has gone into making it far more efficient (approximately 70%).

An outside air connection is standard, meaning that all air necessary to support combustion is taken from outside of the home. No room air is used to support the fire. No vacuum is created in the room when the fire is burning briskly, because the combustion chamber is sealed. Air comes in from outside, feeds the flame and exhausts through the chimney without mixing with room air.

Regular wood stoves and fireplaces use room air for combustion and suck outside air in through every crack, which makes them virtually useless in subzero weather because they bring in cold air faster than they can heat the room.

This stove is primarily a convection heater, although it does provide a radiant heat. Room air is forced through heated passages in the stove by a blower and then it is dispersed through the room as a gentle flow of warm convection air. The stove can also be used for occasional cooking and is designed with a flat top for this purpose.

We opted to heat our new house with a wood stove, because we have enough wood already cut on the property to supply us for several years. We may install a heat pump next year after we have a chance to see how we manage using wood stove, ceiling fans and electric heaters in the more distant rooms. Power interruptions are common in this area, especially in the winter, so we need to make sure we can keep the house warm and cook food even when the power is out.

There is one little problem

The one problem I am running up against is a lack of current data on the construction of protective coverings for the floor and back wall surrounding the wood stove. We picked out a beautiful ceramic tile to protect the floor and wall from the heat of the wood stove, but the stove people seem to think that the weight of the 420 pound stove will crack the tiles, even though they will be mounted on 1/2" Wonderboard.

The tile people say, "No problem!" but they haven't done a stove installation in a very long time. On the other hand, the stove dealer's installers regaled me with a story about a recent installation where they put the stove down gently and the tiles began to creak as they walked away.

I am asking for information from those of you who are currently using wood stoves. What kinds of attractive stone, tile or brick have you found that combines heat resistance with ruggedness? This stove has heat shields on the back and bottom so heat is not the main concern. I look at the cast iron legs with their sharp edges and want to make sure that there is no way that the stoves weight will damage the hearth material under the stove.

I am open to any useful suggestion. Someone even suggested that I put a 24" x 36" slab of slate under the stove and use 12" tiles to cover the rest of the hearth and backstop.

Any suggestions from you experienced wood-burners?

Comments

[Gary M. Whitehair]

Hello David,

I have recently replaced my wood stove in my home in Chestertown, on Maryland's Eastern Shore. We replace a an older wood stove with a Hearthstone Heritage Soapstone woodstove. I did a good deal of research before having the stove installed. I don't think that you can simply install the stove over tile and Wonderboard. You will not have sufficent protection under the stove.

Your stove manufacturer should be able to tell you what R-value is required in the areas around and under your stove to protect you from radiant heat that could cause excessive temperatures and could potentially ignite combustible materials.

For instance, our stove requires a minimum R-value of 1.2. The Wonderboard only has an R-value of .100 and you ceramic tile 0.020. In my judgemet clearly not enough to get you to a reasonable R-value.

I would offer two suggestions. Since you are involved in new construction, simply have a concrete footer poured in the crawlspace area that will support yout stove. Make it obviously the depth of your crawls space and as wide as you need to provide protective areas on each side of the stove. You can then place your backerboard over the entire floor and have your tile installed. This way you support your heavy stove and are fully protected, since concrete has an R-value of .950 per inch. If you don't want to put in the footing, you can use either Micor or Fibrefrax, both are ceramic boards with an R-value of 1.100. The tile can be installed over these surfaces.

I hope this information helps. Sorry for such a long post. But you need to be aware of these issues. By the way I very much enjoy your Blog and read it daily.

[Ray]

I have a cast iron clawfoot tub in my bathroom which I would guess weighs in the 250-300lb range (empty) and it sits on tiles that are those little 3/4" octogonal ones that typically come in white and black. Anyway, even when the tub is full of water (and me at 220 lbs or so) there hasn't been any sort of impact on the tiles.

[Stu]

Have you considered a corn or pellet stove?

I recently installed mine and find it very economical and efficient (85%) and it is rated to be installed into mobile homes so heat and weight are not a real issue.

One unexpected effect is the rather nice odor of popped corn you can barely notice outside the house.

[KPBHD]

In regards to the blower. I have instaled the 2 speed blower on my extra large Dutchwest. My problem is, on hi if im standing about a foot away, I cant feel the air. Now it could be I'm expecting to much out of it, but I'm baseing this on a old coal stove I have in my barn that has a blower, I can stand 15 feet away from it and still fell the air. Any help would be great. Thanks. Kevin

[David St Lawrence]

We have the variable speed blower on the medium size Dutchwest. This blower puts out air in a broad fan from the top of the stove and you can feel it about two feet away.

When our stove is burning well, it will heat up the house (1650 sq ft) to 80 degrees. Most of the time we have to put the damper on to keep the stove from throwing so much heat out.

My only complaint is that the blower is noisy when it is set at the highest speed. We normally operate the blower at about 1/3 speed.

Perhaps you can get a technician from the dealer to come out and look at your stove if it isn't running right.

[Loren]

Hello,
I came accross this site as I was searching for ideas to reduce clearence space for my wood burning stove. I have the Vermont Castings "Defiant" & was wondering what protective covering you decided to use on the floor & wall.

[David St Lawrence]

I used 3/8 inch thick ceramic tile backed up by 1/2 inch backer board which is a concrete and fiberglass composite on top of 13/16 plywood over an air space.

There is a 3/4 inch airspace behind the back part of the hearth and 6 inches of air underneath the bottom portion of the hearth.

My building inspector advised me to raise the hearth for added insulation and for greater ease of use. I actually didn't need the extra insulation because the bottom of the stove barely gets warm, but the added height makes it easier to load the stove.

Do a search for "wood stove" using the search tool on the left sidebar and you will see all of the articles which mention this wood stove and many of them show images which will give you a better idea of the construction.

[Tom Kara]

I have an old King heater, which may not weight as much as the Dutchwest wood stove, but certainly isnt' light either. I added additional joists under the house so that it was 12" OC underneath. Then 3/4" plywood subfloor. On top of that, two layers (instead of one layer) of cement backerboard, with large ceramic tiles on top. There is no evidence of cracking. Tile cracking is a function of floor flex. If you adequately reinforce a framed floor, it should hardly flex if at all unless the weight is truly extreme. I always overbuild when loads may be large. The notion about insulation requirments under these stoves should be backed up by real data about how hot they get underneath. This old King wood stove gets only moderately warm underneath, even with a blazing fire, and the ceramic tile has never been warm to the touch, even with only three inches of air between the bottom of the stove and the tile. I think some building codes are based on unfounded assumptions. I used cement board with tile behind the stove, floor to ceiling, 14" clearance, and it gets only slightly warm. We use a SafetyThimble to go through the wall to a stainless line masonry chimney. There's an article at www.woodheat.org about "The outdoor air myth" for wood stoves which points out that much of the outdoor air supply regulations were based on intuitive assumptions rather than scientific study.