Questions and Concerns in Considering a Catalytic Stove

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UncleMike

New Member
Jun 15, 2022
2
Maine
Hello,

I would like some feedback on some questions I have as we consider a catalytic stove purchase. My wife and I are in her family's 130yr old home in Maine. The original structure is 38x38, two story plus a full attic. The original structure lacks insulation and has horsehair and plaster walls. I am surprised it isn't more difficult to heat considering the above details. The horsehair and plaster must have some R-value!

The family had been supplementing the oil furnace, steam radiator heat by burning wood and bio-bricks in a Modern Clarion cook stove. It even got pressed into duty on Thanksgiving and Christmas to cook one of the two turkeys each year. We lost my father in law in January. As a result that cook stove wasn't kept stoked all day like he used to do. our heating costs soared as a result of using much more oil.

The cook stove has a tiny fire box and my supply of wood is processed accordingly. Max size of our supply of cured wood is 3" x 12". Most of my wood is oak and ash that has cured under cover outside for a year and then another 6 months inside before burning. My principal concern is whether I risk over-firing a new catalytic stove if it is loaded with such small, dry firewood? We also have a supply of bio-bricks remaining from our last purchase. Can we use that fuel in a catalytic stove, even if sparingly?

A second concern is how cold do things need to be outdoors for the potential for chimney condensation and icing of the water vapor from the wood? Is it mostly a concern in arctic type climates and temperatures or is there a specific outdoor temperature that it becomes and issue. The principal concern is that with the extended burn times of these stoves, it would probably be burning after we left for the workday and if doing so is a concern. I am considering a small for the square footage sized stove to be able to run it at a med to medium high heat level to prevent the potential for chimney icing.

I welcome advice on these items as expressed above:

1) over-firing concern from using small, dry wood as well as bio-bricks
2) chimney icing of condensation...how concerned should I be or when should I be concerned
3) would having a small for the footage stove and run it hotter to compensate, reduce the risk of chimney icing

Thanks!

Mike
 
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bholler

Chimney sweep
Staff member
Jan 14, 2014
28,733
central pa
Hello,

I would like some feedback on some questions I have as we consider a catalytic stove purchase. My wife and I are in her family's 130yr old home in Maine. The original structure is 38x38, two story plus a full attic. The original structure lacks insulation and has horsehair and plaster walls. I am surprised it isn't more difficult to heat considering the above details. The horsehair and plaster must have some R-value!

The family had been supplementing the oil furnace, steam radiator heat by burning wood and bio-bricks in a Modern Clarion cook stove. It even got pressed into duty on Thanksgiving and Christmas to cook one of the two turkeys each year. We lost my father in law in January. As a result that cook stove wasn't kept stoked all day like he used to do. our heating costs soared as a result of using much more oil.

The cook stove has a tiny fire box and my supply of wood is processed accordingly. Max size of our supply of cured wood is 3" x 12". Most of my wood is oak and ash that has cured under cover outside for a year and then another 6 months inside before burning. My principal concern is whether I risk over-firing a new catalytic stove if it is loaded with such small, dry firewood? We also have a supply of bio-bricks remaining from our last purchase. Can we use that fuel in a catalytic stove, even if sparingly?

A second concern is how cold do things need to be outdoors for the potential for chimney condensation and icing of the water vapor from the wood? Is it mostly a concern in arctic type climates and temperatures or is there a specific outdoor temperature that it becomes and issue. The principal concern is that with the extended burn times of these stoves, it would probably be burning after we left for the workday and if doing so is a concern. I am considering a small for the square footage sized stove to be able to run it at a med to medium high heat level to prevent the potential for chimney icing.

I welcome advice on these items as expressed above:

1) over-firing concern from using small, dry wood as well as bio-bricks
2) chimney icing of condensation...how concerned should I be or when should I be concerned
3) would having a small for the footage stove and run it hotter to compensate, reduce the risk of chimney icing

Thanks!

Mike
Chimney icing is not a concern at all. Condensation forming creosote is a concern. But if run properly with dry wood that danger in minimal. One of the main benefits of a cat stove is being able to run them at low output cleanly
 
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moresnow

Minister of Fire
Jan 13, 2015
1,980
Iowa
Horsehair wallboard with zero insulation. I feel your pain! My house has/had the same setup essentially.
130 yr old house.
Maine.

I would not fear putting in a good-sized stove. Research the Blaze King Princess model or Woodstock Absolute Steel or Ideal Steel. Those are well respected catalytic stoves with a good track record and plenty of forum users here and elsewhere that have them, for helping guide new stove owners.

Over firing is generally a non-concern in these stoves.
Chimney icing is a non-concern.

Existing chimney condition and wood supply/moisture content may be your real concern. The newest stoves will all require a venting system that meets or exceeds the manufacturers requirements.

The wood supply will really only let the stove perform well if it is truly dry. 20% moisture content on the inside surface of a fresh split is your target.

1.5 years seasoning on your Oak may or may not be long enough for proper moisture content. Guessing the Ash may be fine. Grab a moisture meter from the Box or hardware store. Grab a selection of your splits randomly and re-split them for a quick immediate test on the freshly exposed inner surface (never the end grain). About the only way to confirm.

Good luck and welcome to Hearth.
 
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Ashful

Minister of Fire
Mar 7, 2012
16,576
Philadelphia
What's the home's construction? Plaster on masonry, or framed?

I have two cat stoves, BK30's in a home that's now 288 years old, and I'm loving them. I hear great things about Woodstock too. It may come down to your homes construction and cosmetic preferences to dictate which model is more appropriate.
 

Poindexter

Minister of Fire
Jun 28, 2014
2,721
Fairbanks, Alaska
I will defer to @begreen on sizing for your home. He has an encyclopaedic knowledge of all kinds of stuff and is probably (I won't be at all suprised) familiar with horsehair insulation.

In the BK like I would look at either the 30 sized boxes or the Princess, but I am not familiar with other manufacturers similar models. An elder with a bunch of experience can get a metric crap ton of heat out of an old cookstove with a tiny firebox. I can think of a couple crusty old sourdoughs up here who do the same, it seems to me they are burning enough wood to keep all the metal in the stove hot, and letting the hot metal heat the air. Sort of moderate and slow, there is an art to it for sure.

38x38 as 1444 sqft, x 2 stories, in Maine, with unknown insulation technology, and trying to lower the oil bill. I am leaning towards at least a 3 cubic foot firebox.

Small very dry pieces shouldn't be a problem in any catalytic stove. If you have an air leak you will have a problem no matter what size your fuel is.

The thing about icing and creosote is temperature drop. Combustion is going to be around 600-800 degrees F in a catalytic stove unless you are really ripping it and ejecting subatomic plasma out of the combustor. The flue gasses are going to have a bunch of steam, and little particles of soot. As the gasses rise up the flue they cool, the steam eventually condenses as water and the soot particles stick to the wet spots.

In 'moderate' weather you shouldn't have any trouble running a detached plume, where there is a visible gap of clear air right at the chimney outlet, with maybe some desert mirage waves of heat in it, and then a few inches away the visible plume starts. That means dry steam all the way up your pipe and no creosote accumulation.

In 'cold' weather, you are going to have visible water vapor coming right out of the chimney. Can't be helped. When it is cold enough outdoors, the gasses in the flue will cool enough for the steam to condense into water droplets before they exit the chimney. When that happens you are condensing 'some' water onto the inside of the flue at the top, and 'some' soot is going to stick to it. New burners here (I was one) often start out cleaning the flue after every single cord a couple times, then go to brushing their own pipe every two cords, then four cords. I pretty much brush my pipe out twice annually, about once every four cords. I don't need to do it that often, I could probably brush every six cords without getting nervous, but I burn about 8 cords annually, so planning on every four (twice annually) I don't have to put the hyphen in the AR about when I brush in mid winter.

You are going to want a good quality flue pipe, double layer with an air gap seems to be most common. That air space in between the two layers of pipe will help the flue gasses stay hotter longer, so less creosote buildup. If you are running a modern catalytic stove at kind of mediumish I would be looking for reloading the stove twice daily and having a typical flue gas temp about 400dF (give or take) measured 20-30 inches up the pipe from the stove. In moderate weather you will have a detached plume blah blah.

Curious how much little wood your father in law was burning annually in the old cook stove.
 

Poindexter

Minister of Fire
Jun 28, 2014
2,721
Fairbanks, Alaska
PS: As @moresnow already pointed out, the ongoing challenge with catalytic stoves is feeding them fuel at or drier than 20% moisture content. Oak doesn't grow here, but the consensus on this site is two years of seasoning for oak to burn well in catalytic stoves.

For biobricks, it depends on which ones. The NIELS (Northen Idaho something something) are probably not commonly available in Maine, but you could stuff your stove full of those and not burn any wood at all, if you got the $$$. The cheap ones I can get local, basically oversized pellets (they swell up a lot when I set them on fire), 2-3 biologs in a box full of cordwood is about the limit.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
NIELs and Homfire Prest-Logs are very densely packed, but they log-shaped and hold their form to the end of the burn, unlike the cheap sawdust logs. They're easier to find on the left coast. BioBrick is a brand. They are a good product and densely packed, made in CT, so more available back east. I had to have them sent to me in order to test. BioBricks are in rectangular brick format. Burned properly, they are good fuel. ECO bricks and Redstones are also compressed bricks of decent quality.
 
Last edited:

EbS-P

Minister of Fire
Jan 19, 2019
2,704
SE North Carolina
Thinking longer term here. Do you plan on using cordwood or will you continue with the bio bricks? I’m reading the reasoning for a cat stove is the long burn times. But remember a 3 cu ft stove puts out the same amount of heat (give it take for the efficiency difference) per load wether it’s a cat stove or not.

I don’t own a cat stove. Here are my thoughts about the down sides if I owned one. I don’t have consistent firewood. Pine, oak, poplar, cedar. What ever i can get for free I’ll burn. Some is knotty some is limbs. Reading the forum you will find those that really dual in their BKs have a much more consistent species, size and dryness of firewood than I do. I could become pickier but it might not always be free. Now I’m sure I could always get a 12 hour burn down here in the south sink it’s not really and issue but. You need to at least attempt to quantify your Heating demands. You can always make a BK burn last 12 hours but will you be warm enough? The cost was the real reason I don’t have one. I tried to justify it. Could make the numbers work as it was a second stove.

Upsides. Low and slow is just what I need most of the year. 12 hour Burns and even heat would really be nice.

Just things to think about.
 
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peakbagger

Minister of Fire
Jul 11, 2008
7,344
Northern NH
My guess a poorly insulated home in Maine is going to go through 6 to 8 cords over a winter to heat the entire house. Generally, folks with homes like that heat one or two rooms to be warm and the rest of the house stays cool. A cape is somewhat well laid out for that use in that the upstairs rooms are usually bedrooms. With that sort of yearly wood volume the temptation is shortcut drying times and that means keeping hot combustion temps and lots of moisture going up the stack and inevitable creosote issues. If you burn a stove wide open it can usually handle damp wood but forget turndown.

A building of that vintage is going to have single panes with sash pockets and loose doors. My guess is probably an 800 gallon plus year house. At current rates that is a $4000 plus heating bill on oil. The state is going to encourage you to put in electric minisplits but given current power pricing that means very high electric bills. The only real alternative is you need to cut the heating demand of the house. Look around and see if there are any energy audits available through your utility, state or local governments. Look into weatherization programs you may qualify for. Odds are a blower door test is going to identify air leakage into the house as the biggest bang for the buck, with insulation coming in second. Odds are there ar lots of easy leaks to fix usually in the basement. Having insulation blown in be it cellulose or foam can make a big difference if done by a competent contractor. My guess is there are lot of improvements to reduce heating cost that will pay off in one winter.

Once the place is tightened up, then think about an optimal wood stove.
 

begreen

Mooderator
Staff member
Nov 18, 2005
93,868
South Puget Sound, WA
In our area, low and slow heating could be for 4-5 months of the year. Lighting up a daily fire when the daytime temps move up to 60 is a pain in the butt. A heat pump is much better suited for this task and in some parts of the country much less expensive. It's much cleaner too.
 
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Ashful

Minister of Fire
Mar 7, 2012
16,576
Philadelphia
Hey @peakbagger, you just described my house, but I'm in PA rather than Maine. I find the cat stove works well, in just loading 1x or 2x per day, regardless of actual heating needs, and letting the oil-fired central heating modulate the final few degrees on top of that base charge. I'm still buying 1000 gallons of oil per year, but my heated space is several times larger than the OP's, and that's rough half what I'd be buying without the addition of wood.

begreen makes a great argument for his climate. I'm not sure how that would play against ours, but I'm sure there's some part of the year where a minisplit would be more efficient, in any climate.
 

rijim

Feeling the Heat
Jan 19, 2009
258
RI
I burn Envi blocs in my BK Ashford, since my stove is sized such that I very seldom need to run it with the CAT at the high burn rate, and my chimney does not have excessive draft, I can control the burn rate well. Do you have any larger splits you can mix with the smaller? If the CAT stove is sized such that you don't run it at max burn all the time and the chimney does not have excessive draft then you should be able to manage a CAT stove. Not sure that you won’t have problems overfiring a non-CAT stove with small dry splits.
 

UncleMike

New Member
Jun 15, 2022
2
Maine
I will defer to @begreen on sizing for your home. He has an encyclopaedic knowledge of all kinds of stuff and is probably (I won't be at all suprised) familiar with horsehair insulation.

In the BK like I would look at either the 30 sized boxes or the Princess, but I am not familiar with other manufacturers similar models. An elder with a bunch of experience can get a metric crap ton of heat out of an old cookstove with a tiny firebox. I can think of a couple crusty old sourdoughs up here who do the same, it seems to me they are burning enough wood to keep all the metal in the stove hot, and letting the hot metal heat the air. Sort of moderate and slow, there is an art to it for sure.

38x38 as 1444 sqft, x 2 stories, in Maine, with unknown insulation technology, and trying to lower the oil bill. I am leaning towards at least a 3 cubic foot firebox.

Small very dry pieces shouldn't be a problem in any catalytic stove. If you have an air leak you will have a problem no matter what size your fuel is.

The thing about icing and creosote is temperature drop. Combustion is going to be around 600-800 degrees F in a catalytic stove unless you are really ripping it and ejecting subatomic plasma out of the combustor. The flue gasses are going to have a bunch of steam, and little particles of soot. As the gasses rise up the flue they cool, the steam eventually condenses as water and the soot particles stick to the wet spots.

In 'moderate' weather you shouldn't have any trouble running a detached plume, where there is a visible gap of clear air right at the chimney outlet, with maybe some desert mirage waves of heat in it, and then a few inches away the visible plume starts. That means dry steam all the way up your pipe and no creosote accumulation.

In 'cold' weather, you are going to have visible water vapor coming right out of the chimney. Can't be helped. When it is cold enough outdoors, the gasses in the flue will cool enough for the steam to condense into water droplets before they exit the chimney. When that happens you are condensing 'some' water onto the inside of the flue at the top, and 'some' soot is going to stick to it. New burners here (I was one) often start out cleaning the flue after every single cord a couple times, then go to brushing their own pipe every two cords, then four cords. I pretty much brush my pipe out twice annually, about once every four cords. I don't need to do it that often, I could probably brush every six cords without getting nervous, but I burn about 8 cords annually, so planning on every four (twice annually) I don't have to put the hyphen in the AR about when I brush in mid winter.

You are going to want a good quality flue pipe, double layer with an air gap seems to be most common. That air space in between the two layers of pipe will help the flue gasses stay hotter longer, so less creosote buildup. If you are running a modern catalytic stove at kind of mediumish I would be looking for reloading the stove twice daily and having a typical flue gas temp about 400dF (give or take) measured 20-30 inches up the pipe from the stove. In moderate weather you will have a detached plume blah blah.

Curious how much little wood your father in law was burning annually in the old cook stove.
Between real wood and Bio-Bricks I would estimate it at about 4 cords. That cook stove required attention every 45 minutes or so. My principal reasons for a more efficient unit is the longer burn times and much better efficiency. It will be nice to know that we will be getting heat out of the new stove overnight.