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Manufacturers' Maximum Heating Area Numbers

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by thechimneysweep, Dec 9, 2007.

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  1. thechimneysweep

    thechimneysweep Minister of Fire

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    Let's say you're a wood stove manufacturer, and need to publish heating capacity numbers so potential buyers can compare your various models to each other and the competition.

    You know that people all across the country are going to see the same brochure.

    You also know that your potential customers are going to want to heat their homes in the coldest weather, which in North America occurs in January. So, you consult the National Average Weather Chart at http://www.infoplease.com/ipa/A0762183.html to see how cold that is. Here's what you find out:

    The average January temperature in Seattle, WA is 40.9 degrees.
    The average January temperature in Mount Washington, NH is 5.2 degrees.

    Obviously, your stove models aren't going to heat the same size homes in both locations.

    So, let's say you have produced a stove with a lab-verified absolute maximum output of 97,000 btu/hr. You know that people in the real world aren't going to burn that stove wide open all the time to achieve that output, but you need to give them some basis of comparison to your other models (and the competition), so you publish that number in your brochure, being sure to label it as a "peak" or "maximum" number. Let's say you've also found that this model will heat a well-insulated, single-story, 3,000 sq.ft. house with 8-foot ceilings in Seattle. You publish "heats UP TO 3,000 sq.ft." in your brochure for the same reason. trusting your dealers to interpret the adjustments necessary for their climate zones and for the particular houses to be heated.

    All manufacturers do this, and it does provide a valid standard of comparison from one model to another, when properly interpreted.

    I've noticed when people ask the forum about wood stove sizing, some members respond by asking about the house, and where it is located, like a good, experienced dealer would do.

    Others respond with blanket statements like, "The manufacturers' numbers are crap: reduce them by half."

    I can testify from personal experience that a homeowner who follows the latter advice and puts a non-catalytic, EPA approved woodstove rated to heat up to 3,000 sq.ft. in his 1,500 sq.ft. well-insulated, single-story house in Bellingham, WA will find that, if he operates the stove at secondary ignition temperatures as he's supposed to do, he's going to be enjoying his fire from out in the yard. By the same token, as recently posted on the forum, a homeowner with the same stove installed in a partially-insulated walkout basement in a two-story, 3150 sq.ft. house in MI might find that stove not quite up to the task.

    Not trying to start anything here, just suggesting that people come to the forum for good advice, and we should take care to provide just that.

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  2. nshif

    nshif New Member

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    My thoughts exactly, well said. Another variable you didnt mention is the type of wood used. Someone in an area of primarily soft wood isnt going to get the same results as someone with good hardwood.
  3. thechimneysweep

    thechimneysweep Minister of Fire

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    Bingo. Same goes for dryness of wood, amount and type of window area, chimney updraft, size of splits or rounds, volume, frequency and manner in which the stove is loaded, coriolis effect, etc. OK, maybe not coriolis effect.
  4. webbie

    webbie Seasoned Moderator Staff Member

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  5. Gibbonboy

    Gibbonboy New Member

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    I think you hit the nail on the head, Sweep. There are so many variables thrown in from not only climate, construction, wood type, etc., but also from the human element that I think it's impossible to accurately state a number that you could stand behind. Maybe the stove companies need to find one house in Iowa or something, let us all walk around it in the winter to see what it's like, then they give us their numbers, and we all have a common point of reference i.e., "that guy's house in Iowa".

    I really look at firebox size (or a close extrapolation from outside dimesions if not provided) and BTU output. Once again, a number with some huge variables attached. But doing heat-loss calculations is an immensely important part of designing HVAC calculations, so why is such a thing NOT used in this industry? Add a 20% "new and improved idiot" factor, and recommend a stove based on that figure? Or is it the resolute DIY aspect that lingers, people just want to buy the stove they want, and that's it?

    When I bought my wood furnace, I looked at the BTU's that I really need to heat this house in below-zero weather. No "stand-alone" stove put out that kind of heat, so I was forced to look into the central units. I couldn't afford a Caddy, and realize that I will burn much more wood than a stove user, so as long as I can accept that, this unit is fine. Of course, my insulation campaign continues, continually reducing the heat loss in my home. I couldn't really tell you what "square footage" rating my furnace has, because it was the benchmark with the MOST variables. Not sure if "efficiency", "GPH" or "BTU's" are next in line, but they're all just guesses. Educated, maybe, but still guesses. An experienced dealer/advisor will ascertain as many of these variable items as possible before making a recommendation. And I'm talking about a real professional, not the lawnmower salesman hawking OWB's on the lot.
  6. begreen

    begreen Mooderator Staff Member

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    Thanks for a great summary Tom. At times, I may seem a bit of a pain by requesting, almost in a mantra, info about the locale, the house, the interior, the flue, etc. But I'm not comfortable recommending a stove or insert to someone without a basic understanding of their needs. And to complicate matters, two different, same-sized houses can be next door to each other yet have completely different needs based on layout, insulation, design, etc.
  7. stoveguy2esw

    stoveguy2esw Minister of Fire

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    so, what your saying is , for the manufacturer's numbers not to be "crap" the manufacturer would have to list a heating capacity for every situation and every region. "if you live in seattle use this table, unless you are installing in a basement , then go to page 52 of the brochure, or divide the square footage claim by the square root of your "r" value" thats insane, and completely unreasonable to ask of a manufacturer. i agree that the numbers listed are best case, thats why they say "up to X amount of square feet" not , "this will heat this amount every time" its the same with most all products. think about gas mileage claims in cars, do you honestly think the same car is going to get the same mileage in a mountainous area as it will in a flat area? but GM doesnt have to specify any farther than hwy v/s city. with stoves , you cant even use zones like plant seed companies use to tell when to plant them. cause joe blow might have r42 in his ceiling and r19 in the walls, and the next guy might have single pane windows and no insulation in the same size house. heck ive talked to people who heat an area twice as big as rated, but ive also talked to those who say it wont heat a room. bottom line, when we run a stove down the line , we dont know what the house it goes in is going to be , insulated or not , in south carolina or alaska. so we post best case and explain that its "up to" anyone got a better idea without having to print a brochure that looks like an LA phone book?
  8. Highbeam

    Highbeam Minister of Fire

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    As a buyer I expect the manufacturer to disclose a particular area heated with conditions. Not every town in teh country and every insulation level possible. One particular and defined situation is plenty. Even better would be if all manufacturers chose the same situation, the guy's house in Iowa was ideal.

    Trouble is that every manufacturer wants the edge. So they might say it heats 3000 SF in Seattle knowing that is it won't do it in MI but that they'll get more sales in MI since perhaps the MI folks will trust the 3000 SF figure.

    I vote for a standard house in Iowa to which all stoves are compared. I'll adjust for my insulation and location.
  9. Gooserider

    Gooserider Mod Emeritus

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    Well I think there are several different parts of the problem...

    1. From watching the posts on the forum, it seems that there is an overwhelmingly large tendency for people to get stoves that are undersized - I see at least 10 complaints about "my stove doesn't heat well enough" or "my burn time is to short" for every "my stove runs me out of the house" post. I think this is a combination of manfacturer understatement of heating capacities, dealers that sell more on the basis of "look at the pretty fire" than on "feel the heat", and customers wanting to save money by getting a cheaper (smaller) stove.

    As a consequence of this, I tend to tell users to "go big", and I think many of the other more experienced members do as well. OTOH, I feel like I sometimes want to argue a bit with Craig because I feel like his advice leads to undersizing.

    2. In the EPA tests, there is a defined "driving course" that describes exactly how the car wil be driven, so regardless of maker, the MPG numbers can be compared to each other with a good level of certainty that if car A gets better than car B in the test, it will do the same in "real life" for me, even if I don't get the exact same numbers the EPA does - and there's lots of experience that will help me estimate a good expectation of what my real world mileage will be if the EPA specs are such and such...

    OTOH, there is no "industry standard climate" or "standard house", or ANSI standard for measuring BTU outputs, so every manufacturer makes their own different (unstated) assumptions about the environment used for making those "area heated" claims, or even the stove heat outputs. Ditto burn times - each measured differently - all of this makes comparison between brands, and sometimes even models, impossible.

    I also say ignore any of the spec numbers other than firebox size - unfortunately the one number that seems least likely to be provided - perhaps because it's the only one that can't be inflated? It seems to me like the best approach is to determine the desired firebox size - based on heating needs, climate, insulation, type of wood available, etc. and desired burn times, then pick a stove in that size class from the possible options.

    I actually tend to think the 2.5-3 Cu.ft size range is the "sweet spot" size that would work for most people, and go up or down from that size reccomendation only when there is a good reason to do so...

    Gooserider

    Gooserider
  10. Bill

    Bill Minister of Fire

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    This is a very interesting topic, I think the dealers should explain to the end user what the stoves are capable of heating. I just bought a new stove this year, to replace a smaller unit. I found for the most part the dealers were no help, they just wanted to sell me anything. With the help of this forum I made my decision what to buy. I do not remember any dealer asking me what size my house was, what type of chimney, insulation, or anything.
  11. jpl1nh

    jpl1nh Minister of Fire

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    It seems to me that the state of the industry has to rely on "art" as much as science. It is the experience here either of the sales and installation professionals or the collective experience of the users that are the guide for those seeking help. It is an imperfect system, and Tom, your post is a great reminder of the humility needed in advising. You miss a couple of factors and your suggestions can be way off. I visited Woodstock stove here in NH and discussed my house here in NH at length with one of their sales reps who suggested the Fireview would be too much stove for my house...my experience with the Keystone so far worries me about the capacity of that stove to heat my home. Reason?? Perhaps its because virtually all winter long we are in the shade of a large wooded hill. Did I mention that to them, did he ask. Maybe he didn't hear how many windows we have, or I over estimated the insulation - whatever, (and I am learning how to tweek every possible BTU out of the handsome little bugger so perhaps its still me) it's another example of the challange of correctly sizing a stove. Great topic!
  12. thechimneysweep

    thechimneysweep Minister of Fire

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    Mike, I'm not sure whose post you're responding to here, but I sense that you might have been skimming a bit when you read my original post. The point you make above feels like a heated rebuttal, but it is the exact point I was trying to make: all a manufacturer can do is supply the optimum values, and trust his dealers to adjust for local climate and the needs of the individual customer.

    Smokey, you illustrate my final point. Those dealers the manufacturer must rely on to qualify a given stove for a given customer often fall far short of that goal, causing confused shoppers to turn to the forum for reliable advice. My message to the forum members was to keep up the good work.
  13. JimWalshin845

    JimWalshin845 New Member

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    Fabulous,

    And what is really missing is how do we move that heat from one room to another. I see so many complaints that 'my living room is 85 but the bedroom on the other side of the ranch house is only 55 degrees'. I suggested at times that you should calculate the BTU's for the areas you will heat.... got so many retorts that this is baloney!

    I see so many people opting for a insert rather than a stove and that really baffles my mind. :eek:hh:

    Yes, aesthetics comes into play and having that appliance as a piece of furniture. It takes dedication and a lifestyle to run a solid fuel appliance. So many don't understand this and don't understand that you need a source that either you will harvest or you have to rely on a supplier that will supply you at a reasonable fee..... very much like a oil/gas dealer.

    I have seen inserts/stoves rated at certain BTU's that could never come close to the brochures advertising. It is a shame that happens. What is great is that there are forums like this one that makes the Buyer Beware.

    Thanks for the great thread,
    Jim
  14. Gooserider

    Gooserider Mod Emeritus

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    I don't see what your issue is here Jim... It is part of our standard set of questions to ask what sort of area the poster wants to heat, and we tend to reccomend based on that area. We also tell people that moving air from place to place can be a challenge - I don't know how many times I've seen it posted that stoves are AREA heaters, not home furnaces... As to the insert vs. freestanding, we usually reccomend what the poster wants - they ask for an insert we suggest inserts, and so on. If they don't know, then I usually see a discussion of each.

    I do know that I tend to not worry that much about BTU's in an absolute sense, I don't find them useful since the stove makers numbers aren't reliable. Far simpler just to go with rough matching the size of the area to the size of the firebox - adjusted for burn-time desired, and stuff like insulation and climate.

    So what's the problem?

    Gooserider
  15. JimWalshin845

    JimWalshin845 New Member

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    Goose,

    No issues except for the fact that many people expect a stove/insert to heat their entire home and are disappointed that it just doesn't work that way. You see it all the time and many of them join this forum with the rant of 'what did I do wrong' or 'this model X stove is not cranked up to what they say'. Many did not do a thorough investigation from the getgo.

    Also, and I think this is significant, someone who has a great room with vaulted ceilings requirements are certainly very different from the standard straight ranch with the same square footage. A stove manufacturer may say it will heat 2,000sf....but will it heat all that open space?

    That is why most of us are here, to get good advice from people who know a broad spectrum of stoves and environments. That is why we look to people like you for an unbiased opinion.

    Going back to Tom's original question..... we wish there was a good standard or a greater authority that the manufacturers have to abide to, but that isn't the case at this time.

    A stove can put out a zillion BTUs as advertised, but how are we going to utilize them properly? It would be great to just plug in numbers into a computer, and the technology is there.

    Without guidance as per placement, draft, safety, type of fuel use, aesthetics we may lose the main focal point of why we use wood as a main fuel source. When a home is designed, a good architect is going to take in all features of the home and size a good reliable heat/cooling source to make the owners feel comfortable.

    Hopefuly, when we go to a retailer they are knowledgeable as per product, install and support and as we see here umpteen times the ball is often dropped.

    This forum helps fill all those voids with suggestions that are well thought out. Yes, we can get caught up as per being biased as per what stove is better than another, but Tom has the right idea as per why people come here for advice... and hopefully we will get great advice and use it to our best advantage.

    Yikes... 63 degrees outside.. gonna put the A/C unit back in the window! :coolsmile:

    Safe journeys and warm burns,
    Jim
  16. begreen

    begreen Mooderator Staff Member

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    Good point Jim. Often the house's glass area and cubic footage is more important than square footage.
  17. jtp10181

    jtp10181 Minister of Fire

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    I only read the main post but I just wanted to add that we have a sign in our showroom that is from Quad or HHT that states the heating capacities for the stoves are targeted for as well insulated home in "Zone 1". There is also a map of the USA with different zones so you can figure it all out. I know we are in Zone 1 which is the coldest zone, but I did not study the rest of the map very well. We usually try to base our sales off the listed sqft capacities and I have not heard many people complain they can't heat thier house. Just the lady who was putting 3 logs in her 7100 and couldn't get heat out of it. I loaded it up and let it rip and she said if it did that when she was using it should would have thought the house was going to burn down, hah.
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