Most efficient way to burn wood

[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.