Most efficient way to burn wood

[3930dave]

I think one of their main advantages is to heat multi buildings at one station. The most efficient ones use maybe a little bit more wood as a wood stove sq footage ratio wise. The not so efficient ones can use double the wood. Other advantages is they are cleaner for the house environs in not only keeping the wood mess outside, but also not breathing in the particulate matter of a wood stove inside the house.

Boilers aren't for everybody, and there have been some badly made ones.

Depending on where you live, external boilers may be easier/cheaper to insure since combustion is external to the dwelling. Dual pipes are pre-insulated, all in one tube (think O pipe diameter), so are efficient and easy to install. They can be useful for retrofits, using a heat exchanger on a forced air setup, and not just radiant/slab heating. Useful for initial or primary domestic hot water heating. Ash is already out of the house; you don't haul wood inside.

Boilers don't make much $ sense for heating a small well insulated space. At the other end of things (space wise), they can make a lot of sense. Attractive in the Ag world, for heating greenhouses. They (Portage and Main) have a large setup for an external (to the boiler) hopper for wood chips, auger driven - for large scale operations that are already dealing with chipped wood, this can make sense.

Like tractors , we all have different needs and preferences when it comes to wood :thumbsup: .

Rgds, D.

 

[arrow]

Thanks Dan. It is very helpful to hear the story side of this endeavor as things can get complicated. Just last night one of the daughters came to visit. I told of her of our plans and you know what she said? "Dad you guys can't move, Twilight ( the horse she had from when she was 5 to 26) is buried here" I said "oh yeah so is Digger (first dog here), all the cats, Liz the chicken, Moe, Larry and Curly the 3 geese Digger eliminated over a two year period when they tried to peck him in the you know what, and all the rest of the 6 other dogs" How could I be so thoughtless.

 

[arrow]

Like tractors , we all have different needs and preferences when it comes to wood :thumbsup: .

Rgds, D.

True dat! (gosh I'm getting hipper)

 

[arrow]

We built our home in 2009 slab on grade then buried the front half so we could have a walk out finished basement. The lower back walls are concrete half way up then wood the rest of the foundation walls are full concrete 12" thick. The house was designed as a one floor two bedroom open floor plan ranch with 1442 sq. feet. In Mass. with our building codes you must us 2x6 construction to pass energy code, also r38 roof and r30 floor insulation. I did not insl. the floor as we planned to heat with wood from the walkout basement that way the heat radiates to the main floor. The first stove we had was my Dads Fisher from 1978 or so. It worked well but burned enough wood to heat two homes and we had to feed it all the time. This past fall we bought a Harman tl300 and retired the fisher to the barn we put up this fall. With the new stove we heated the house all this winter loading it at 5:30 in the morning then again at 4:30 in the afternoon. With the stove in the lower level it heats up the concrete floor and the walls and they give off heat well after the stove temp. has gone down. So far we have used 1 1/2 cords that's one third of what we were using in the old stove. I have propane as our backup heat and put in a Reni on demand water heater that works great . We bought 22 acres of mixed woodlands so we have all the wood in the backyard we will ever need. Good luck with your new home and have fun with the planning and building of it as Jane and I did.

Is wood your main heat source G? I also have my wood stove in the cellar and to this point (starting on the coldest days of Oct and 24/7 as winter settled in) I've used a bit over 4 cord to heat 2300 sq ft. I have to count the cellar sq footage as the stove is heating that as well so 3 floors total. My house is a poorly insulated log home.

 

[GBOUTDOORS]

Yes we heat basically with wood but have a 500 gal. Propan tank in the ground and forced hot air heat system set at 58% 24/7 that only comes on if we happen to not be around for more than 12 to 14 hours . Our total sq. footage is 2644 that's 1442 main floor and 1202 lower walkout floor were the wood stove is. I have a drop ceiling in the walkout area with heat vents in it for the lower zone heat that has never bin run as we have never needed it. But we did have it set up so it can be diverted to the main floor system and by running the blower only it would draw heat from lower level system and stove to the upper and heat that way but again have never used this as The house stays at around 72 lower and 68 main level just by the heat rising thru the floor and the open stairway no fans at all. Only thing is you can not get a co from the building dept. for a house with no insl. in the floor but being a General Contractor for more years than I wish to count and this being my own home it could be done. By the way this was house # 35 of this design that I have built Jane fell in love with it at a 55 and over sub. I was doing and asked if we could do one there but I am only 58 and did not want to be stuck with a bunch over 55 people that's why we bought the 22acres.

 

[Egon]

NOT true this is why i suggested a CAT stove. You basically cut the air back till it smolders, no visible flame on the wood. You will get secondaries that float around at the top of the firebox buring the gasses inside before the rest goes through the CATs to totally combust. If you have good DRY wood and healthy cats and know what your doing you better have that blower on high to get that heat out cause your CAT temps will soar, if i dont cut my air back enough fast enough you will aee 1800F easy on the CAT probe. there designed to burn with low air and do it with ZERO smoke out of the chimney.

So, with a proper design catalytic stove you could burn very hot and get real efficiency.

If the proper combustion air has to be cut back to maintain proper heat something's not being utilized to it's full extent and thus may not be as efficient as could be.

Too much combustion air is not good either.

Can some tell me why using outside combustion is considered efficient?

 

[Egon]

I agree fully. The "stoves" (if you want to call them that) that seem the most efficient are the one's that burn hot but retain the heat energy to give up later. They also weigh around 6000#. I also agree with the house being designed around the stove. Site orientation for solar gain, insulation and internal exhaust seem to be critical. I am also wondering about chimney design. Mass stoves have a long exhaust path extracting as much heat out of the exhaust as possible. Instead of creating this "mass" with the stove design which takes up a lot of floor space, why couldn't one create the mass with the internal chimney? The key here I believe is not to allow the exhaust gases to directly exit out the chimney but instead recirculate before expulsion. Draft might be tricky and I cannot picture this with a 15' tall chimney. With all the right combo's, one may need but a cord of wood all winter which I also cannot comprehend at this moment if wood is the main heat source for 7 months. This floor plan I'm looking at is 54'x32' which is only about a 1700 sq ft house. I love wood furnaces for their ability to convey radiant heat but as someone said, might be overkill.

You will do fine at choosing a system that works for you.:thumbsup:

 

[/pine]

So, with a proper design catalytic stove you could burn very hot and get real efficiency.

If the proper combustion air has to be cut back to maintain proper heat something's not being utilized to it's full extent and thus may not be as efficient as could be.

Too much combustion air is not good either.

Can some tell me why using outside combustion is considered efficient?

to be efficient (using outside combustion air) a fireplace/stove must have glass doors etc...

Along with the gasses (smoke etc.) combustion air as well as the air that gets siphoned along with it...has to come from somewhere...if it's not coming from outside...it has to come from inside...meaning the fire will be sucking outside air in every crack and crevice around windows and doors (creating cold drafts (inside)....outside combustion air eliminates the cold outside air from being sucked into the house reducing the efficiency

 

[lutt]

I think Egon that is because outside air is cooler, denser, so it has more oxygen. I have never had expieranced this with a wood burner. But a gas or diesel engine will benefit from cooler air outside the engine compartment. Also guys, I know we are probly on the same playing field, someone may have metioned this also. But dry seasoned wood is always better. I see the problem with people around here trying to burn green wood, it just doesnt work well. I think that is why alot of people have trouble with smoke coming out of there outside boilers. Green just wont burn worth a hoot. LUTT

 

[Dutch445]

Not sure if anybody has mentioned this yet, but in addition to making the new home airtight and well insulated,
a masonry heater is a wood burning stove that sounds like it would be something you could build your home around, and
heat very efficiently. from what i have read, they sound very comfortable, and easy to use, but i can't speak
for wood consumption.

Masonry Stove Builders - masonry heater manufacturers
https://mainewoodheat.com/masonry-heaters/
http://masonryheater.com

 

[dave1949]

My 1995 Vermont Casting catalytic stove had two air dampers, one for the main fire chamber and second one for the air inlet to the afterburner catalytic unit. So, if designed for it, it is possible to supply air to those two functions independently. That stove made great heat, but the maintenance of the catalytic unit was expensive.

Passive solar and slabs and radiant heat don't always work well together. As Dan noted, a slab thick enough to provide decent thermal mass, is too thick for efficient radiant heat.

For example, we have been on a long cloudy streak for the past two weeks. Not much heat from the sun. If I were to turn on my radiant floor heat in my 8+" thick slab, the boiler would run for at least eight hours before the floor begins to feel warmer. Allowing large temperature variations just doesn't work well for radiant slab heat, and the thicker the slab is to provide thermal mass for the passive solar, the worse it will work.

On the other hand, that thick slab is the key to storing enough heat to get through the long cloudy spells which are going to happen now and then. Our house is actually cooler inside now than it has been all winter with the outdoor temperatures ranging around freezing. I have been burning the Tulikivi and using some electric space heat. For passive solar, it's about the sunshine more than the outside temperatures, and we could use some sunshine now. :laughing:

For those reasons, even though it seemed like a good idea, I would not pair passive solar with radiant floor heat if I had it to do over. You will get a lot more bang for the buck with a wood burner.

 

[westcliffe01]

Just an FYI, boilers can be perfectly fine, even the big ones. The trick (that virtually no-one follows) is to have a large hot water storage tank (sized to suit the output of the boiler) that stores all the heat produced during a "run". You might bury this tank under a barn for instance and let it act as radiant heat for the building in addition to providing heat storage. The the water from this large tank is re-circulated all day. The fire does not smolder but runs at a decent steady rate delivering all its heat to the storage tank.

 

[dmccarty]

Other people's post mades me remember some things I forgot to add in my post....

We do have 2x6 walls though they have big holes for windows. The walls have an inch of rigid foam and are around R25. Attic insulation is R38. The floor has two inches of rigid foam under the slab.

I can't believe I forgot to mention outside combustion air to the stove. :confused3: We have a six inch PVC pipe that runs from the stove to the nearest outside wall under the slab. I bought a PVC cap, drilled a bunch of holes in it and placed screen inside the cap before putting it on the PVC pipe. The pipe terminates behind the wood stove and the plan was to connect the combustion air pipe to the stove. The connection was not needed though. When the stove is burning you can feel air being sucked through that pipe and into the house. Since the pipe is behind the stove we never feel the cold air. My FIL did something similar except he has a fireplace. He has a vent on the floor in front of the fireplace. The vent is connected to a pipe that runs under the slab and outside. When he has the fireplace running you can feel that cold air flow out of the vent but it goes right into the fireplace. Works real well.

For house wall, floor, ceiling, details, use Lstiburek's book for your climate zone, Builder's Guides. Wow, the book prices went up but they are well worth the money. He works with/for Building Science Information which I highly recommend visiting. The site has all sorts of interesting article about construction techniques and such. I used the building guide for my area to specify design details on the walls and floors.

Later,
Dan

 

[clemsonfor]

We built our home in 2009 slab on grade then buried the front half so we could have a walk out finished basement. The lower back walls are concrete half way up then wood the rest of the foundation walls are full concrete 12" thick. The house was designed as a one floor two bedroom open floor plan ranch with 1442 sq. feet. In Mass. with our building codes you must us 2x6 construction to pass energy code, also r38 roof and r30 floor insulation. I did not insl. the floor as we planned to heat with wood from the walkout basement that way the heat radiates to the main floor. The first stove we had was my Dads Fisher from 1978 or so. It worked well but burned enough wood to heat two homes and we had to feed it all the time. This past fall we bought a Harman tl300 and retired the fisher to the barn we put up this fall. With the new stove we heated the house all this winter loading it at 5:30 in the morning then again at 4:30 in the afternoon. With the stove in the lower level it heats up the concrete floor and the walls and they give off heat well after the stove temp. has gone down. So far we have used 1 1/2 cords that's one third of what we were using in the old stove. I have propane as our backup heat and put in a Reni on demand water heater that works great . We bought 22 acres of mixed woodlands so we have all the wood in the backyard we will ever need. Good luck with your new home and have fun with the planning and building of it as Jane and I did. By the way arrow we are in Fairhaven Mass. So the weather here is close to yours. And you do not have to go with a cat. To get the afterburn as the Harman stoves do this with a reburn system as do some of the other top brand stoves. This system has worked great so far for us.

I think like 90% of stoves that are not CAT stoves are "reburn" stoves as you describe it or are Tube stoves as most refer to as how they burn the smoke gases before they leave. They just usually are not as long burning and 99% are not as effecient as a CAT.

Yes CATs do take maintence and new CATs that a tube stove does not but the savings in wood your time and effort into it i think are a good trade off. With less than optimal wood i think 3 years is about right. They say you can get 5-6 yearrrs out of a CAT and some have claimed closer to 10. Now the extreme on that scale is useing at least 3yr old hardwoods which is the unlimite fuel. The goal is wood less than 20% MC. OAk seasoned 1 year still will be in the 30% range.

 

[Singalo]

In six pages, this has probably been mentioned, by I'm going to go with an answer of "Fire". Fire is the most efficient way to burn wood. I also suspect that this was a trick question

 

[Rustyiron]

Some good links pertaining to this topic;
GreenBuildingTalk - Green Building Forums on Insulating Concrete Forms (ICF), Structural Insulated Panels (SIP), Radiant Heating, Geothermal Heat Pumps, Solar Power, Green Construction Projects sip's, icf's, radiant, insulation etc.
Solar analysis tools help with passive solar gains
A Simple DIY Solar Space and Water Heating System more stuff to think about
Hearth.com Forums Home a real good "conversation" on wood heat, boilers, stoves etc.

 

[soulasphil]

MY PELLET HEATING AND HOT WATER : To go into detail, pellets here are bought by the metric ton (1.000 kilograms). Delivered in bulk and blown into your silo they are 250 euros a ton (cheaper and no trouble at all, except there is sometimes too much dust with the pellets and you risk stalling your feeding system). Delivered to your door in 15 kilos plastic bags they are 310 euros a ton (more expensive and you have to take them yourself through the house to the silo). I burn approximately 2 tons a year. To the price of pellets you must add a little electricity to run the system and have the burner and chimney professionnally cleaned once a year.
Pellet burners have an extremely high efficiency provided they are run at full capacity all the time. So the principle is to heat a 500 liter water tank from which the system can then draw calories for heating or hot water as needed. Two computers are used, one to run the burner itself, the other to regulate temperature according to the day of the week, the hour of day, your mood and so on (I personally appreciate the program cycling hot water when we generally need it so that it immediately comes hot out of the tap without having to wait for the tubing to empty itself).
The black tube on the floor in picture one is the screw bringing the pellets to the furnace when required.

 

[3930dave]

Just an FYI, boilers can be perfectly fine, even the big ones. The trick (that virtually no-one follows) is to have a large hot water storage tank (sized to suit the output of the boiler) that stores all the heat produced during a "run". You might bury this tank under a barn for instance and let it act as radiant heat for the building in addition to providing heat storage. The the water from this large tank is re-circulated all day. The fire does not smolder but runs at a decent steady rate delivering all its heat to the storage tank.

I remember reading about a owner-built chalet, way up north. He cleaned up large sections of a steel modular (erector set approach, for on site assembly) fuel storage tank, from an old military installation. Ended up with a good sized round swimming pool, sitting on the concrete pad of his chalet. Plumbed it up to a heat exchanger he built for his wood stove, and he had a great thermal mass to use, and also swim in !

Simple trick, but as you said, not often done.

Rgds, D.

 

[dave1949]

MY PELLET HEATING AND HOT WATER : To go into detail, pellets here are bought by the metric ton (1.000 kilograms). Delivered in bulk and blown into your silo they are 250 euros a ton (cheaper and no trouble at all, except there is sometimes too much dust with the pellets and you risk stalling your feeding system). Delivered to your door in 15 kilos plastic bags they are 310 euros a ton (more expensive and you have to take them yourself through the house to the silo). I burn approximately 2 tons a year. To the price of pellets you must add a little electricity to run the system and have the burner and chimney professionnally cleaned once a year.
Pellet burners have an extremely high efficiency provided they are run at full capacity all the time. So the principle is to heat a 500 liter water tank from which the system can then draw calories for heating or hot water as needed. Two computers are used, one to run the burner itself, the other to regulate temperature according to the day of the week, the hour of day, your mood and so on (I personally appreciate the program cycling hot water when we generally need it so that it immediately comes hot out of the tap without having to wait for the tubing to empty itself).
The black tube on the floor in picture one is the screw bringing the pellets to the furnace when required.

You guys are way ahead of us in bulk pellet systems, but there is some activity in that market.
Maine Energy Systems offers alternative biomass energy through automatic wood pellet boiler heating and bulk pellet delivery.

Your 250 Euro per (2,200 lb metric?) ton is in the same neighborhood as pellets by the 2000 lb ton in 40 lb bags here. I see prices here ranging from $180 to $240 per ton--you haul.

 

[Scooby074]

One thing for sure, my next house will be ICF construction.
And it will have hydronic heating of some sort. We have electric infloor in the bathroom and it is AWESOME. SWMBO wont live without it now.

As to the heat source. Gasification wood boilers are near the top of the list. There are some nice, computer controlled european units that look awesome. Whatever I choose, it will be in an outbuilding and plumbed into the house. Both for fire safety and for ease on fuel storage and maintenance.

It will likely have water thermo storage. That will enable the easy installation of solar later. It's easy to DIY this with a large, used propane tank.

Another system near the top is wood chips. IMHO it will be less work that solid wood and easier to mechanize. I hope to have enough land (and large enough tractor to run a decent chipper) to where harvesting my own biomass becomes an option. A unit like a Froling T4 would be ideal. Portage and Main makes a chip boiler that is worth consideration, but it is considerably more crude than the Froling.

Bulk pellets are also a good option, but that will have to wait until we have home delivery of pellets like they have in europe in order to see any savings. The T4 above is pellet comparable for when bulk pellet becomes an option.