Wood consumption - OWB vs add-on wood furnace

Arborist Forum

Help Support Arborist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

fields_mj

Addicted to ArboristSite
AS Supporting Member.
Joined
Dec 27, 2008
Messages
1,463
Reaction score
1,119
Location
Indiana
I live in Central Indiana. Normally in mid Jan highs are in the low 30s, and over night lows are in the low 20s, but we normally get a few stretches of near or sub-zero weather. I'm in a poorly insulated 2,000 sq ft ranch. If it's 45 and Sunny outside, the house will stay around 70 deg without any other heat (AC bill in the summer really sucks...). I currently have an add-on wood burning furnace that was manufactured in 1980. It either needs to be rebuilt or replaced in the next few years. The unit is located in my basement next to my central air system, and feeds hot air directly into my cold air return just prior to the furnace filter. This supplies most of my heat, but the NG furnace will kick on as needed if I let the wood burner die out. I normally burn around 4 cords of hardwood (mostly hickory with some Oak, Locust, and a little Ash) in a season (Thanksgiving through early March), but on a really cold year with several weeks of near to sub zero weather I have burned as much as 6 cords. I'm debating replacing it with an OWB, but I'm concerned that my wood usage will increase substantially. Is there anyone out there who's used both an add-on furnace and an OWB that can speak to whether or not one consumes noticeably more firewood than the other? For an OWB, if I go with a gasification unit, I would likely go with a Classic Edge from Central Boiler. If I go with a non-gasification unit, it would likely be a Heatmor.

Thanks in advance,
Mark
 
I don’t have an owb, I have a kuuma vapor fire 100 wood furnace. It’s set up just like you, tied into the ductwork. My furnace was roughly 6,000 delivered and installed. It has no problem keeping my brand new house warm (1500sqft). They say it’s the only one that officially pass the 2020 emmisions spec. The fire cheif/shelter models are supposed to pass but I think there is some fishy work with the testing process.
When I looked at an owb for my new house, it was 15,000 for the unit, not including the heat exchangers, underground tubing....

Long story short. I think your better off investing in a new furnace and some insulation or new windows. All that money spent on an owb won’t keep your house cool in the summer.


Sent from my iPhone using Tapatalk
 
Mark, This is a tough question and hard to compare without hard facts. I had 8 seasons with our Empire gasser and just replaced it with a Heatmaster G200. We heated our 3000sq ft house for 6 years on 6 cords of pine per year. I then built a 4200 sq ft shop with radiant heat and we jumped to 12 cords of pine a year.
We love heating with wood but I have to say if we had access to NG I'm not sure wood would be our primary heat source.
Growing up with a basement wood furnace I can tell you I really enjoy all the wood mess being outside with an OWB and I handle the wood less.
I would say there are several additional costs to installing a OWB that need to be considered in the cost analysis.
 
If you have natural gas, burning wood is not financially smart in my opinion. I have NG and an OWB, that the previous owner bought for 6k for the unit alone I have an 800 sf house with a 200 sf porch that I only heat when I am in it, I have hot water heat,I also have about 2000sf of shop space, that I do not intentionally heat, but the OWB is in the shop space so it stay above 50 at all times I keep the house at 60-66 depending on time of day, it is an old house but moderately well insulated, I also have a ng boiler. I burn at least a heaping contractor wheelbarrow of wood per day, and two wheelbarrows per day when the temps are in the teens and below. OWBs burn a lot of wood. It may cost $200 per month max if I were to heat only with gas. Do not buy an OWB spend the money on insulating, windows, etc. Get like a foot of insulation in your attic. Maybe a high efficiency furnace. If you like the wood work, keep your current side shooter thing. If I could trade the OWB I have for all the money the PO put into it and the installation I would take the money all day everyday, and I even enjoy the wood work.
 
The Kuuma's are great if you want an indoor. Awesome product. I am on my 4th year with CB classic edge 550. My house was built before 1900 and is approx 5000 sq ft. I have new windows, roof, basement, etc that are less than 15 years old. I keep mine at 72 all heating season and will use between 8-12 cord. I have yet to fill my OWB up this year because of temps. I strive for a 12 hr burn time and that has been 1/3 to 1/2 fills. This year I burnt basswood during oct to mid nov with no issues. I will not leave it lay or refuse to cut it. During the normal cold times I burn oak, hard maple, ash, elm. I will use less wood than my buddy with a heatmor non gasser and my house is twice his size and 70 years older. If the wood is dry the gasser makes full use of it.

Downfalls are your wood needs to be dry and you usually strive for shorter burn times than a smoke dragon. If you have specific questions about the CB I would be glad to answer them.
 
Also I forgot to mention that, my owb/own, developed a crack where the loading door opening connects to the firebox about 10yrs after the date of manufacture, and I would assert that it is not uncommon for these units to only last 10yrs. Luckily I have the ability to weld well enough to fix most things. But for many it would have been trash after 10yrs so that is 600 per year just for the unit not including tubing installation, pumps etc..
 
I don’t have an owb, I have a kuuma vapor fire 100 wood furnace. It’s set up just like you, tied into the ductwork. My furnace was roughly 6,000 delivered and installed. It has no problem keeping my brand new house warm (1500sqft). They say it’s the only one that officially pass the 2020 emmisions spec. The fire cheif/shelter models are supposed to pass but I think there is some fishy work with the testing process.
When I looked at an owb for my new house, it was 15,000 for the unit, not including the heat exchangers, underground tubing....

Long story short. I think your better off investing in a new furnace and some insulation or new windows. All that money spent on an owb won’t keep your house cool in the summer.


Sent from my iPhone using Tapatalk
My house was built in 1959 and had the original double pain Anderson windows in it when we bought it in 2015. I've been replacing them one room at a time for the past 5 years. I've added a substantial amount of insulation to the attic, and I've re-insulated the exterior walls as I've remodeled each of the bedrooms and the bathroom. The next rooms on the list are the kitchen and living room in that order. The living room has 16 feet of windows that are 7 feet tall, and the kitchen has 8 feet worth of the same windows. I won't see a noticeable change to my heating/cooling cost until all 24 ft of those windows have been replaced. I'm currently saving for the kitchen remodel. It will be a major remodel project, and it's too much for me to do on my own (north of $50K). Realistically, I won't see a noticeable change to my heating and cooling needs until I've completed $75K to $100K worth of remodeling projects. I'll get there, but it's going to take another 7 or 8 years. In the mean time, I will need to do something for heat.

My current unit is somewhat similar to the Fire Chief/Clayton design. I almost bought one of those when I installed mine. You could buy them at the end of the season for $750 back then. Money was pretty tight at the time so I went with a used furnace off Craigslist for a few hundred dollars. My thinking was that I would pocket the savings on my fuel bill and use that to replace the furnace when it wore out. I had no idea it would last for so long, or that things would be SO much more expensive now. The furnace is in the basement, and it's NOT a walk out basement. I was able to wrestle the unit down into the basement with the help of a much stronger friend. We are both noticeably older now, and trying to get the old unit out of the basement, or getting a new one down there would involve a trip to the ER. Installing a new furnace in the basement will involve modifications to the foundation and basement wall, and digging an external entry way. The stairway will be removable (not easily, but removeable none the less), allowing heavy and/or bulky items to be lowered into the basement via mechanical or hydraulic means. Another sizable remodeling project, but one that will facilitate some critical needs 20+ years from now.

So my options are paying a professional welder to rebuild my existing unit where it sits, installing an OWB, or going back to using only the NG unit that was installed in 1994. If I went with an OWB, I would likely treat it like buying a vehicle and look for a lightly used unit (since I'm not in a hurry). The biggest deciding factor at this point is wood consumption. I have access to plenty of good firewood, but it's an hour drive each way. I make it work because I have a loader, a 4wd ton truck, 13K winch, and a 12,000 lb equipment trailer that allows me to load, transport, and unload 2 cord per trip keeping everything in log form until I'm able to process it in the back yard at my convenience. Adding 2 more cord (50% increase) means an extra Saturday or two worth of work. Not a big deal. If it doubled to 8 cord, that's not a possibility. If an OWB is only half as efficient as an add-on furnace, it would make more sense to put the money into digging a new basement entry. I just can't believe anyone would ever bother installing an OWB if it's only half as efficient as the add-on wood furnaces that were built in the 1970's.
 
The Kuuma's are great if you want an indoor. Awesome product. I am on my 4th year with CB classic edge 550. My house was built before 1900 and is approx 5000 sq ft. I have new windows, roof, basement, etc that are less than 15 years old. I keep mine at 72 all heating season and will use between 8-12 cord. I have yet to fill my OWB up this year because of temps. I strive for a 12 hr burn time and that has been 1/3 to 1/2 fills. This year I burnt basswood during oct to mid nov with no issues. I will not leave it lay or refuse to cut it. During the normal cold times I burn oak, hard maple, ash, elm. I will use less wood than my buddy with a heatmor non gasser and my house is twice his size and 70 years older. If the wood is dry the gasser makes full use of it.

Downfalls are your wood needs to be dry and you usually strive for shorter burn times than a smoke dragon. If you have specific questions about the CB I would be glad to answer them.

My house was built in 1959 and had the original double pain Anderson windows in it when we bought it in 2015. I've been replacing them one room at a time for the past 5 years. I've added a substantial amount of insulation to the attic, and I've re-insulated the exterior walls as I've remodeled each of the bedrooms and the bathroom. The next rooms on the list are the kitchen and living room in that order. The living room has 16 feet of windows that are 7 feet tall, and the kitchen has 8 feet worth of the same windows. I won't see a noticeable change to my heating/cooling cost until all 24 ft of those windows have been replaced. I'm currently saving for the kitchen remodel. It will be a major remodel project, and it's too much for me to do on my own (north of $50K). Realistically, I won't see a noticeable change to my heating and cooling needs until I've completed $75K to $100K worth of remodeling projects. I'll get there, but it's going to take another 7 or 8 years. In the mean time, I will need to do something for heat.

My current unit is somewhat similar to the Fire Chief/Clayton design. I almost bought one of those when I installed mine. You could buy them at the end of the season for $750 back then. Money was pretty tight at the time so I went with a used furnace off Craigslist for a few hundred dollars. My thinking was that I would pocket the savings on my fuel bill and use that to replace the furnace when it wore out. I had no idea it would last for so long, or that things would be SO much more expensive now. The furnace is in the basement, and it's NOT a walk out basement. I was able to wrestle the unit down into the basement with the help of a much stronger friend. We are both noticeably older now, and trying to get the old unit out of the basement, or getting a new one down there would involve a trip to the ER. Installing a new furnace in the basement will involve modifications to the foundation and basement wall, and digging an external entry way. The stairway will be removable (not easily, but removeable none the less), allowing heavy and/or bulky items to be lowered into the basement via mechanical or hydraulic means. Another sizable remodeling project, but one that will facilitate some critical needs 20+ years from now.

So my options are paying a professional welder to rebuild my existing unit where it sits, installing an OWB, or going back to using only the NG unit that was installed in 1994. If I went with an OWB, I would likely treat it like buying a vehicle and look for a lightly used unit (since I'm not in a hurry). The biggest deciding factor at this point is wood consumption. I have access to plenty of good firewood, but it's an hour drive each way. I make it work because I have a loader, a 4wd ton truck, 13K winch, and a 12,000 lb equipment trailer that allows me to load, transport, and unload 2 cord per trip keeping everything in log form until I'm able to process it in the back yard at my convenience. Adding 2 more cord (50% increase) means an extra Saturday or two worth of work. Not a big deal. If it doubled to 8 cord, that's not a possibility. If an OWB is only half as efficient as an add-on furnace, it would make more sense to put the money into digging a new basement entry. I just can't believe anyone would ever bother installing an OWB if it's only half as efficient as the add-on wood furnaces that were built in the 1970's.
Your house sounds pretty cool, I love windows, my last house had a glass sunroom about 18x18 with a glass roof, that was between the kitchen and living room, but I closed it off during the winter it was all modern double pane. No matter what it costs a lot to heat a space with a lot of windows. What is the efficiency rating of your current furnace. I did forget to mention my house has 20 windows, 4 windows in the basement, and the somewhat heated porch is also all windows (all windows are newer), so that may have some bearing on wood consumption, the tubing run from the OWB/IWB is also about 100'
 
My run from boiler to home is 100' as well. It cost me more but I used thermo pex and have almost zero heat loss between the two buried about 36" inches.
 
My father in law has an own, in his shop, that heats the shop, house and spring house. He used to have 2 indoor wood boilers that heated the same spaces. His is made by Greenwood, it is vastly more efficient then his old set up, with the added bonus he splits very little. Think it can take all but a 20" round chunk, 24 to 28" long. He went from around 12 cord a year, down to 8 to 9 cord. Sadly they arnt made anymore, that I know of. I have no experience with any other brands of owb.
 
I live in Central Indiana. Normally in mid Jan highs are in the low 30s, and over night lows are in the low 20s, but we normally get a few stretches of near or sub-zero weather. I'm in a poorly insulated 2,000 sq ft ranch. If it's 45 and Sunny outside, the house will stay around 70 deg without any other heat (AC bill in the summer really sucks...). I currently have an add-on wood burning furnace that was manufactured in 1980. It either needs to be rebuilt or replaced in the next few years. The unit is located in my basement next to my central air system, and feeds hot air directly into my cold air return just prior to the furnace filter. This supplies most of my heat, but the NG furnace will kick on as needed if I let the wood burner die out. I normally burn around 4 cords of hardwood (mostly hickory with some Oak, Locust, and a little Ash) in a season (Thanksgiving through early March), but on a really cold year with several weeks of near to sub zero weather I have burned as much as 6 cords. I'm debating replacing it with an OWB, but I'm concerned that my wood usage will increase substantially. Is there anyone out there who's used both an add-on furnace and an OWB that can speak to whether or not one consumes noticeably more firewood than the other? For an OWB, if I go with a gasification unit, I would likely go with a Classic Edge from Central Boiler. If I go with a non-gasification unit, it would likely be a Heatmor.

Thanks in advance,
Mark
Have you researched the new Drolet Heat Commander furnace? It sounds impressive. There is a ongoing review by a couple new owners on another site. Sounds very easy to operate and very efficient. Betting the new models are lighter than some of the older versions also? Possibly.

Why cant you get/hire help bringing in a new furnace the same way you got the last one in ? Did the basement access change?

When I hear guys talking about pushing 8-12 cord a year through a OWB I cringe. No problem if I was in my 20' or 30's. Noooo way I want to be tied to CSS that much wood now. Not to mention the financial investment.
 
The windows are what sold us on the house. The view is really nice. The windows just need to be replaced.

If I lived on property that could supply the wood I needed, I would be more willing to use more firewood for heat. Since I have to travel to get it, that severely limits what I can do.

As far as getting a new furnace down into the basement, it was a precarious process last time around. Multiple tight turns coming through the house, including a tight turn at the top of the stair way. I've since installed new flooring on the main floor, and and I'd rather avoid damaging it. As I mentioned, my existing NG furnace was installed in 1994, and I think it's a standard 85% unit. I just put a new blower fan in it 2 weeks ago. No complaints since I've been running it non-stop, almost year round for over 15 years now... Eventually, the NG furnace will have to be replaced so the external entry would be useful at that time also. Additionally, I have a few fireproof safes that I'd like to move to the basement. In short, an external entry for my basement would be useful ;) I have not yet priced adding an external entry to the basement, but I'm guessing that it will cost a significant amount. Just another piece of the puzzle that needs an answer. I suspect that if I add an external entry to the basement AND buy and install a new Kuuma Vapor Fire100, I'll right around the same cost as installing a new OWB. I say that tongue in cheek, but it's probably not far from the truth.

So what I surmise from all of this discussion is that for those who have to rely on fuel oil/electric/propane, an OWB may be a good option. This is especially true if you have convieniant access to large quantities of firewood and/or live in northern climates where day time highs often struggle to get out of the teens, and any day above freezing is somewhat of a heat wave. However, if a person is spending less than $1,500 to $2K per year on heat, an OWB doesn't make sense. Seems like owners are tickled pink if the unit lasts 20 years meaning that the capitol cost alone depreciates at a rate of $500/year and sometimes twice that. Conversely, my 1980 add on furnace has lasted 40 years with minimal maintenance, and the replacement cost for a new, deluxe model add-on furnace would be less than 1/4 the cost of installing a new OWB. None of that takes into the account that an OWB will burn at least as much wood as I'm using now, and could actually double my wood consumption with the only benefit being that the mess is now kept outside instead of in the basement. FWIW, my mess for an entire season will roughly fill a 20 gal trash can, so not a huge amount. Decision made. OWB is off the table. Thank you everyone for your input! The next question will be which add-on furnace to purchase, but that will be a new thread :)


Thanks again,
Mark
 
When I hear guys talking about pushing 8-12 cord a year through a OWB I cringe. No problem if I was in my 20' or 30's. Noooo way I want to be tied to CSS that much wood now. Not to mention the financial investment.
I'm also heating 5k sq ft in a older home. I'm in my mid 40's and honestly it maybe takes a week to put that much up. You are correct though it wasn't cheap. However my alternatives are fuel oil or propane. If I had NG I would still burn wood but definitely as a second. I don't know many people up north that keep there house at 72 that don't burn wood.
 
Decision made. OWB is off the table. Thank you everyone for your input!
I think you have made the right choice for YOU with all the detailed info you have provided.

For ME, the OWB is the right choice. But I say that you have to want to do it and it's not for everyone. And I built and installed it myself so it paid for itself the first year. I burn ~9 cord per year for a 2500 sq ft house with 25' ceilings. Keep in mind that includes some wood that the wood snobs here would turn their noses up at (and you know who you are.) I do cut/split/stack most of it but I have learned to set aside the difficult pieces as overnight burns. Generally there is less time to process the same amount of wood for an OWB (longer splits, larger splits, and less stacking) If I had all hickory, I would dare say I could be at ~6 cord.
 
2 fold answer here.
Straight up tell you you'll burn more wood with OWB unless it's radiant.

BUT if you have easy access to wood then OWB will be the better option.
Been burning wood for over 40 years and you can't beat the long burn times of a boiler and peice of mind.....no chimney fires, no smoke in the house and no wood roaches flying around.
And my favorite part is I don't have to be particular about cut lengths and don't have to spend much time splitting.
 
Purchasing the OWB is only half of the overall cost typically...all the little things needed for install really add up!
And you will burn twice as much wood in an OWB as with a Kuuma furnace.
 
I didn't read every response but before I bought any stove I would invest in new windows, doors and insulation. I enjoy cutting and splitting but as I get older I don't want to do any more than I have to. Those things will pay you back on a daily basis winter, summer, spring and fall. Then get an OWB and enjoy the warmth.
 
I have a wood furnace and supplement my heat with wood. I burn less than 3 cord a year. I either get 1 tank of propane a year or 1 every other year. A OWB would be to much for just my 1700sqft ranch from the 70s and if I had NG I'd switch to a stove or fire place in my living room to add some extra warmth on cold nights. As far as a new wood furnace it will be nothing like your old one. I have an epa one that does not meet the 2020 specs which is fine with me. I vote wood furnace.
 
Back
Top