I know the consumption, will that help size a Garn

Without doing a heat load calc on your building it's all heresay and guesses.

35,000,000btu per week is an ungodly heatload. This is not a house, correct? That works out to 208,000 btu/hour on average. Most homes average something closer to moving the decimal point to the left one slot...

Harvesting and processing this kind of quantity is quite a task. I wouldn't even think about burning wood with these numbers. I feel like processing 3-4 cord per year is about my threshold...

What is the data you found? As Stee* said, without actual heat loss data, guessing at cord useage is not a reliable exercise. I have never burned more than a single cord in a MONTH, and my house is not at all well sealed or insulated. If you think you are actually going to burn 2 cords in a week, I suspect you will be burning on average 12 hours out of every 24 with a GARN. Get a handle on your heat load and then hit us up with the data.

BTW - if you are anywhere close to that rate of heat loss, consider nothing less than a WHS2000. It is not that much more than a 1500. And you can still add a 1500 or another 2000 if demand warrants and finances permit.

This type of questions is posted so often. I realize that most of us are 'do-it-yourselfers', but if you do not know how or will not learn how to do a heat loss calculation, hire a professional. The average cost of an installed system seems to be 20 to 30 thousand dollars! An energy audit and professionally modeled heat loss calculation will cost no more than $400 or $500, and the suggested retrofits will probably save you time and money on both the initial investment in equipment, and less time and fuel over the life cycle of the system.

The GARNs probably last 30 years or more. Here, you are talking about spending $12,000 (for one)-25,000 (for two) just for the boilers, possibly 35 grand for something you may have to visit every day for decades, but are reluctant to spend 400 bucks to find a reliable and accurate number to use to size the equipment properly. Even if someone could tell you "You absolutely need one GARN 1500", next you would be asking what size pipe should I use? Then, what size circulator do I need, and so on. The answer to all of these questions starts with a complete audit of this specific building and a proper heat loss model which identifies the peak BTUs/hr that are required.

vondera said:

This type of questions is posted so often. I realize that most of us are 'do-it-yourselfers', but if you do not know how or will not learn how to do a heat loss calculation, hire a professional. The average cost of an installed system seems to be 20 to 30 thousand dollars! An energy audit and professionally modeled heat loss calculation will cost no more than $400 or $500, and the suggested retrofits will probably save you time and money on both the initial investment in equipment, and less time and fuel over the life cycle of the system.

The GARNs probably last 30 years or more. Here, you are talking about spending $12,000 (for one)-25,000 (for two) just for the boilers, possibly 35 grand for something you may have to visit every day for decades, but are reluctant to spend 400 bucks to find a reliable and accurate number to use to size the equipment properly. Even if someone could tell you "You absolutely need one GARN 1500", next you would be asking what size pipe should I use? Then, what size circulator do I need, and so on. The answer to all of these questions starts with a complete audit of this specific building and a proper heat loss model which identifies the peak BTUs/hr that are required.

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That is very very good advice and it's inconceivable that it would need further elaboration.

Now, after saying the above, and assuming you actually have a heating load of 208K you will find yourself firing a 1500 every 4 hours, a pair of them will go 8. This is based on the fact that a 1500 will dissipate approximately 750,000 btu's when you drop the water temp from 200-120*.

What is your altitude Durango? That may be a clue as to why the Garn folks are recommending a 1500.

Note: The burn rate on a 1500 or a 2000 is shy of your load if it's honestly 500K. Come to think of it 500K for a 5500 sq ft building is almost 100 btu/sq ft. That's almost what we drive a snow melt system with. Does you building have windows and doors in it or just holes in the walls?

I'm assuming there is no chance of any work to tighten up the building or any insulation at all? That is a lot of wood to burn.

I Never thought I would say this, but I would burn oil.

2 cords a week if your calculations are correct(I can't possibly see how, I think that would heat my back yard...) Is going beyond impractical. You would need to be loading wood nearly full time, or hire someone to do it.


Heat loss like that is beyond uninsulated. You must have some air gaps that you could probably say forget caulk and spray foam and start shoving furniture into the cracks to seal them up.

I would either get some insulation in there, hire out to have the place sealed up professionally, and get some new calculations done. Those estimates really sound funky.

karri0n said:

I Never thought I would say this, but I would burn oil.

2 cords a week if your calculations are correct(I can't possibly see how, I think that would heat my back yard...) Is going beyond impractical. You would need to be loading wood nearly full time, or hire someone to do it.


Heat loss like that is beyond uninsulated. You must have some air gaps that you could probably say forget caulk and spray foam and start shoving furniture into the cracks to seal them up.

I would either get some insulation in there, hire out to have the place sealed up professionally, and get some new calculations done. Those estimates really sound funky.

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Then again...........a half million btu worth of oil equates to a little over 3 gallons an hour. I have a couple commercial/ag jobs out there doing that right now and they pay about $4000 a month in the Dec-Feb time period. I can cut and stoke a lot of wood for $12,000.

My advice would be to tighten up the structure as much a possible and then consider the wood burning aspect of the energy use equation.

karri0n said:

Heat loss like that is beyond uninsulated. You must have some air gaps that you could probably say forget caulk and spray foam and start shoving furniture into the cracks to seal them up.

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I don't care who you are.....that was funny!

Is this located far outside of town/city? How do most in the area heat? Being a B & B, depending on your electric rates, it might be better to zone heat with electric baseboard. Customers could choose exactly what temp the room is, and unused rooms wouldn't need the BTUS when not in use. Look at the overhead costs for the equipment and installs, and you might come out saving a considerable amount of money vs. wood.

I'm still trying to wrap my head around this as I live in an area of uninsulated sprawling farm houses and -30 C winters. They burned about 15-20 cord a winter but of course the extremities of the house were cold as the dickens. I suppose if you tried to heat them fully they would take that kind of wood.

Is there any opportunity to isolate part of the building? Lot of the farm houses shut down the second floor in the winter and closed up the summer kitchen.

You say you had a fan test, was the house so leaky they couldn't pressurize the house enough to get results?

Is there plumbing in the place now? When pumping that much heat into a place a short break in the heating could spell a very expensive disaster.

fwiw, i am new to this, but first i would think about sourcing something with more btus than pine, and second i would tend to distrust the heat loss calculations as very overstated. i do not think the ones i have seen are set up to cope with the quirks of big old odd irregularly insulated buildings.

i have a big old odd house. i have run two online heat loss calculations, and gotten results that bear zero relationship to my actual btu consumption. if i trusted the raw results i get, i would look to generate 250-300k btus to heat the house, but it seems for the last 20 years at least it has been heated with a 140,000 net btu output boiler set to generate 125,000 btu, and for the last 85 years it has had only 140,000 btu worth of radiators. as noted in another thread, it appears to be undersized, but it works.

one other thing, if it's got a restaurant, can't the kitchen heat a good part of it?

I would tend to agree with the statement that many heat loss calcs will overstate the actual load. A manual J heat loss calc does not take any internal heat gains such as lighting, appliances, cooking or bathing so that has to get added into the mix. A person also has to bear in mind that manual J was set up by engineers who as a rule operate with a heavy dose of C.Y.A. and tend to err on the conservative side of things. Nothing wrong with that per se but just something to keep in mind. That being said, I would find it abnormal for a heat loss to be as far off as the above poster has stated. Usually I see maybe 10-15% at most.

i think the potential for innacuracy increases as square footages on old houses increase. i am by no means a professional and these were online calculators but i dutifully plugged in my numbers and then had to keep adjusting upwards in terms of insulating properties. there was no way to accurately answer questions about the r value on the walls etc.. so i had to guess. on one program i had to assume i had r20 in the walls and ceiling and increase the r value of the single pained windows to double panes to get my actual consumption last winter, and last year was a cold window.

by the way, heaterman can you recommend a good online calculator? i am anxious to do this right to try to figure things out.

To the top of page poster, I suspect beetle killed pine is the main cheap wood available at that altitude.

The coal stoves make sense, would have been a lot less material handling.

The town sounds interesting, I read a story about a similar town, perhaps the same one. Are you isolated in the winter from normal traffic?

Durango said:

I have at last found some matching data locally on a comparable building and the amount of energy they need to heat it through the winter.

A good guess is that in a bad week I will be burning about 2 cords a week of pine, say 35m btu's, which certainly ties in with everything else.

I have also been put in touch with somebody who has 2 2000's, but it is their first season and they are a lot lower down.

I was thinking of going for one 1500 and probably having to add another. If we really need it/can afford it.

For those who are actually burning, does 2 cords a week sound practically do able?

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Just for clarification - what dimentions are these cords?

Just found this thread. Very interesting.
My wife and I live in a 120 y/o farm house, approximately 2,200 sq ft, essentially NO insulation, and original windows. We have an Empyre 450 OWB, and easily burn 1.5 cords per week January and February. I load the chamber at 7AM and 7PM. When I load it there is just a nice but small bed of coals, I need to put a FULL load of wood into that baby. We will be converting our barn into our home, and already have the GARN 2000 which will be heating that space. Although the barn/home will be more on the order of 8,500 sq ft (footprint is 3,700 sq ft....at 36'x104') we believe we will be able to heat using the GARN 2000, and firing twice a day (and the chamber of the GARN 2000 won't hold but a third of the wood the Empyre 450 will hold).
We imagine the Empyre OWB is about 35% efficient - vs 80-85% for the GARN once on-line.
We will be spraying closed cell polyurethane foam on the OUTSIDE of the barn/home (then an application of elastomeric paint over the foam to protect it from UV and 'the elements').
The 3" of SPF will be applied 3' below grade to the top of the barn, and back down to 3' below grade on the other side. That is, the monilithic application of 3" of SPF (+ elastomeric paint) will be our insulation, siding, and roof.
Our realistic expectation is that we will have a measured/calculable R-value of near 60 for the structure as a whole....much like that of a monolithic dome home.
http://www.monolithic.com/stories/r-value-effective-60

We have completed the SPF application from 3' below grade and up 8' of the (outside of the) concrete walls of the former milking parlor. We also applied 2" of SPF to the underside of the hay mow floor. This former milking parlor space has three 36"x80" doors, two 7'x9' garage doors, and 14 30"x60" windows. That 3700 sq ft space is currently 'heated' only by the 50F to 55F temp of the ground PASSIVELY coming up through the concrete floor. SPF job was completed late November. Temps in SW Wisconsin have been near freezing to 14 below zero outside......and never has the temperature of the area in the former milking parlor dropped below 33 degrees F. There is NO active source of heat for that space. Note also, we are not done back-filling, so we expect the space to be 'warmer' next winter, and we'll only need to heat the 'basement' from 40F up to whatever we want.

The crew who did the SPF job said they increasingly have people spray their entire structure, on the outside, with foam.
Over a year ago they did a combination bar/restaurant that way. The owner is over-the-moon about his heating bill. His heating bill for 2008/2009 was 1/3 what it was for 2007/2008.....and remember he's talking dollars...and in 2007/2008 fuel costs were significantly less than in 2008/2009.
I'd say - get some sprayed foam insulating done.....and you might need only a single GARN 2000!...or you could load two of em 2x per day even when it is bone-chilling and windy outside.
BTW - once we have our barn/home livable....we will bull doze the home we are living in. (The home we are in is about 300 feet from the barn-to-be-home).
Hankovitch in SW Wisconsin