Sq ft heating claims

[EatenByLimestone]

Is it fair to the homeowner or even to the retailer to put a square foot heating claim on a space heater like a woodstove?

There seems to be too many variables to it and it seems to set most up for disappointment.

Matt

 

[thephotohound]

Matt -

I agree. My immediate reaction is that they originally came up with this form of measure to simply breakdown the hourly BTU rating to a concept that the layman could more easily understand. I would assume that these estimates started out conservative, but competition ensued, and before you know it, you have sq ft claims at the top of the range instead of the bottom. Now the below average insulated house with 30 yr old windows finds that the stove he bought to heat "1200 SF" won;t heat his 1000 SF ranch. I think the only solution is to (like anything else) do your homework. Like I always say, when in doubt, RESEARCH!

 

[Corie]

Often, these square footage numbers are relatively arbitrarily picked. Go by the BTU ratings provided by the manufacturer and from the EPA hang tag. They will give you a better idea of what you can expect. IN order to properly size a stove, one REALLY needs to calculate the BTU loss from their house on the coldest day of the winter and then find a stove that can match that BTU loss at the top end of its performance range. If all else fails, use the firebox size, burn rate and efficiency of the unit to calculate an ACTUAL BTU output of the stove, because many of the manufacturers ratings are inflated, self promoting numbers that are almost impossible to reproduce or would require the stove GLOWING to reproduce.

 

[Backwoods Savage]

I agree PH. Probably the best way, at least what we found, was to figure anywhere from 50% to 70% of what the claims are is much more accurate.

It is the same thing for how long you can get heat from a stove. For example: Our Woodstock Fireview says it will hold a fire for 12 hours and still have enough hot coals to start the next fire with. Well, that is true.....to a point. If the stove was stocked to the hilt with perfectly seasoned oak, hickory, apple or some such wood and the stove turned way down and then the draft never opened more than it was at the start, that stove indeed probably would give some heat for 12 hours and have coals at the end.

However, in real life, that claim is nothing more than marketing people's ideas of heating a home or whatever. In real life, you do damper that stove down else the thing would overheat for sure. But let's say I load the stove up when I get up in the morning. I'm stuck in the house all day and it is cold outside with a driving wind. After 3-4 hours I notice that the temperature of the stove is starting to drop, so I open the draft a little bit and it comes right back. Everyone is comfortable. Another hour and it gets opened a little more. Soon the draft is opend either all the way or very close to that because all that is left is coals.

Now those coals will not keep the stove pumping out the heat that you want....and it's only been 6 hours since you stocked up the stove. So, do you continue to burn the coals down before adding more wood? If so, the house will cool as the stove will kick out maybe 350 degrees maximum. (We have found that if we add just one more log while burning down the coals it does work quite well.)

The problem with the above is that the claim is for 12 hours of heat! Not so in real life!! Yes, I can get 12 hours with the outdoor temperature in the 30's or above but not when it gets cold.

So, always take marketing people's figures with a grain of salt. Remember that marketing people live in a different world and think (an oxymoron) much different than most folks do.

 

[BrotherBart]

Often, these square footage numbers are relatively arbitrarily picked. Go by the BTU ratings provided by the manufacturer and from the EPA hang tag. They will give you a better idea of what you can expect. IN order to properly size a stove, one REALLY needs to calculate the BTU loss from their house on the coldest day of the winter and then find a stove that can match that BTU loss at the top end of its performance range. If all else fails, use the firebox size, burn rate and efficiency of the unit to calculate an ACTUAL BTU output of the stove, because many of the manufacturers ratings are inflated, self promoting numbers that are almost impossible to reproduce or would require the stove GLOWING to reproduce.

I calculated what the heat loss would be if the roof blew off and then bought the 30. :coolgrin:

 

[Gooserider]

I'm of the opinion that the only number that really can't be fudged very much by the manufacturer is the firebox size. I think that firebox size is a good cross model / brand comparison tool because it can't be fudged, and it's repeatable to a large extent... I have seen very little evidence that EPA approved stoves of a given firebox size will vary significantly in heat outputs, burn times, etc. if operated the same way, with the same wood, etc. You might get a little longer burn time out of a cat, but not a significant amount in the overall picture. In part because of EPA rules limiting how far you can turn the stove down, and in part because of the inherent burning characteristics of wood, you know about how much heat you can get out of a given size firebox, either when it is doing a low burn, or when it's cranked.

Thus, you know what firebox size will give you the burn times you want, defined the way you think is most meaningful - not the way the marketers decided to cook the numbers. The firebox size also gives you the approximate range of heat you can expect...

Of course, this is also a number that seems harder to find than the marketing competition numbers - It seems to be left off of many brochures, etc.

Gooserider