# Wood stove BTU numbers VS. The real world



## Alan Gage (Feb 21, 2011)

I've tried searching but haven't been able to come up with what I'm looking for. Namely, how accurate are the stated BTU numbers on wood stoves?

My reason for asking is that I'm building a small and very well insulated house this spring and will be heating it with wood, hopefully 100% (electric backup). It will be a single level, open floor plan, and probably a little over 900 sq. ft. 

I've run it through Rescheck and done some online heat loss calculations and while I realize they're probably not entirely accurate I'm coming up with a heat loss for the structure of between 17,000-20,000 BTU/hour at -20 degrees. 

I've already ordered an Englander 17-VL since it was on sale so I'm kind of locked in on that but I need to nail down placement. Englander gives the stove a peak BTU reading of 40,000 BTU/hour. I'm assuming this is ideal conditions and that I can't expect to get that much heat out of it for very long before it starts tapering off. But what _can_ I expect to get out of it? What percentage of peak output can I expect for a stove with a nice load of oak after burning for 3 hours? 5 hours? 8 hours? A nice graph showing the BTU output of a wood stove stove over an 8 hour burn would sure be helpful. 

If I can realistically expect to get 30-40K BTU out of the stove I'll be more inclined to put it where I want, which is pretty close to some windows. If real world numbers will be considerably lower I'll look at a more centrally located position along an interior wall.

Any input appreciated.

Alan


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## wellbuilt home (Feb 21, 2011)

I think the heat out put is ok if you don't see -20 very often . 
  The problem will be in fire box size  ,  1.1 cf is small for  a over night burn .
  I think you will only see peak heat for 2/3 hours then another 2 hrs of warn temps . 
  My minimum fire box size would be around 2cf  just to get a good 6 hr burn . 
  40,000 btus seems like a lot to get from  1.1 cf fire box . 
 If you want to sleep all night you will need to go bigger .
                                                                                        John


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## joefrompa (Feb 21, 2011)

My 2.2 cubic foot firebox will likely give off 30-40k btu's at peak running conditions (not peak temps) and with the fan on high. I can probably squeeze that range out for 90 minutes max. Lopi says ~70k btu can be extracted, but my guess is that's with the blower all the way on high and the stove top at the very top of the possible safe operating range.

As John said, your problem is likely be to one of size. You'll want to have some perfectly sized LARGE pieces to put in there before bed to give you anywhere near acceptable output for 6-8 hour stretches.

That being said, at 900 square feet with outstanding sealing and insulation, you should have very little loss too. So if you can get the place cozy, it might get a little cold after a nights rest but you might find that perfectly acceptable.


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## jimbom (Feb 21, 2011)

Your stove will be fine, it is the house to watch.

My little Atlanta AC5 steel stove is rated at 34,000 Btu/hour and it will do that just fine.  However, I have to tend it a little more than if I just cruise at 20,000 Btu/hour.  I am sure you will be warm regardless of stove location.  Especially if you make sure you use house wrap, foam/tape all the penetrations in the wrap and the top and bottom plates, and seal all electrical and plumbing openings in the ceilings, floor, and walls.  My experience is air leaks are very correlated to heat loss.  I am not sure heat loss calculation methods have a very good way of accounting for leaks.  There is the crack method and the air changes methods, but really, these are hard to apply before construction completion.  So my bottom line for you is if you get a tight house, you will be warm with the stove you have ordered.

Another thing to consider is the really few hours per year when you will be running at or near the design temperature.  My design temperature is 0 F.  On a thirty year average, only 9 hours per year does it get colder than 0 F.  Only 18 hours is it 0 to 4 F.  Only 40 hours is it 5 to 9 F.  Almost all of these low temperatures are recorded from midnight to 8am.  So out of the 8760 hours in a year, I have a few where we might have to cuddle up or light off the AC5.  And we do, because I have a tiny heat plant.  No excess capacity at all.  It is much more efficient that way.  

For fun I looked up Duluth IAP, Minnesota.  I show a design temperature of -20 F (I have old data, so this may have changed).  Only 22 hours below -20 F.  Only 40 hours from -20/-16. And only 90 from -15/-11.  So a heat plant that was maxed out at -20 F would only have 22 hours per year when it would need a 5 F boost from standby heat or when the indoor temperature would be 65 F instead of 70 F.  Sadly, very few American homes are sized close to requirements.  Many designers add 20 to 50% extra capacity just to be safe.


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## joefrompa (Feb 21, 2011)

Also, consider installing an outside air kit so that your stove is pulling cold air from the outside of the house and sending it up the chimney, and your room gets all the radiant effects without having the stove sucking up some conditioned air. This is even more pertinent in a newly constructed, well-sealed house.

My guess is that you'll find yourself heating the house to the level of toasty quite easily.


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## Battenkiller (Feb 21, 2011)

It's best to look at some burn cycle charts to get a little illumination on this.  In the real world, peak output is almost never close to the rate a given device will output over an entire burn cycle.  Very few makers send their stoves out to get tested in calorimeter rooms (the only real test), so they use stack loss data against fuel weight loss data (with the stove sitting on a scale) to get realtime estimates.  

In essence, if a stove is placed on a scale and charged with a load of wood, and realtime stack losses show that the stove is burning at "X" combustion efficiency over a certain time, the loss in weight x the efficiency factor x low heating value of the fuel (usually about 7800 BTU/lb for wood containing 20% water by weight) x duration of the burn = heat output for that time period.  It can be extremely accurate, but in the case of the EPA tests themselves, much of the stack loss is unaccounted for because the EPA doesn't really care about anything except for PM (at this point in time, at any rate).

Bottom line, expect an average heat output of about 1/3 or less of the "peak" output over the course of a cold-to-cold burn cycle.


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## SolarAndWood (Feb 21, 2011)

If I run wide open with the blowers on high, I can do 85K using the 7800 BTU/lb method.  The manufacturer states 47K as real world with 90K theoretical max.


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## Battenkiller (Feb 21, 2011)

SolarAndWood said:
			
		

> If I run wide open with the blowers on high, I can do 85K using the 7800 BTU/lb method.  The manufacturer states 47K as real world with 90K theoretical max.



My stove is rated at only 50K, so I guess I'd need two of them side-by-side to get the output of a single BKK.  Wouldn't want to be in the same room with them, though. %-P


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## Alan Gage (Feb 21, 2011)

Thanks for the replies. I realize I'll have problems getting long burns from such a small firebox but I'm ok with that. If I have enough coals left over in the AM to light some small splits I'll be happy. I actually prefer a house cooler than most. 70 degrees and over I start getting uncomfortably warm. 

BK - An average heat output of 1/3 or less from peak over a burn cycle would give me lots of room to play so that's good news. Even if it averaged 1/2 of peak output I should be sitting pretty.

Jimbo - Good point about the amount of time the outside temp actually stays at the design temp. It was colder than average here this winter but we never made it to -20. Lots of nights of 10-15 below and highs around 0. Last year we hit it a few times as well as setting a record of -32. But like you said, it doesn't stay there long. I've tried running the numbers with design temps of -10 and -15 and it certainly helps out. 

You're right about calculating air loss, that will be the wild card. I'm going to be very careful about building a tight envelope. The plan is 2x6 walls full of cellulose insulation, OSB sheathing, housewrap, and at least 2" of rigid foam on the exterior (with taped seams). That will give me another R10 as well as creating a thermal break for the studs. Flat ceiling with at least R-60 blown in. I've never lived in a well insulated and tight house so I'm really interested (excited actually) to see how well it holds heat.

I'm also worried about the stove being too hot for the majority of the burning season. I'm used to burning 24/7 from December through the end of February. I'm afraid the house will hold heat so well that except in the coldest weather the coals will be burned down to nothing before it's time to reload. Which will mean starting a fire from scratch most of the time, which is a pain. That's one of the reasons for wanting to place it by some windows, to let some of that heat get away. But I don't want to lose too much of it and run out of BTUs when it gets really cold. I suppose I can always break down and turn on the backup heat if that's the case.

I guess there are worse problems to have....like trying to heat my current house with the wood stove when it's -10 and the wind is howling. 

Thanks for all the great info everyone!

Alan


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## Alan Gage (Feb 21, 2011)

BTW, Battenkiller, that's one of my favorite Bob Dylan songs.

Alan


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## VCBurner (Feb 21, 2011)

I think you would have been better off with tha 13-nc for the longer burns with those outdoor temps you stated.  Especially since you plan on doing most of the heating with your stove.
Good luck with the new stove.


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## Jimbob (Feb 21, 2011)

Here's another heat-loss calculator to try, just for kicks:
http://www.h-mac.com/heat-load-calculator/heat-load-calculator.php

It would be interesting to see if it gives you the same #'s you have.
At any rate, 20,000 btu/hr is good. If your stove is slightly too small, it would be VERY cheap to supplement it a bit with the electric on the coldest days.

At 7800 btu/lb. you'd be burning about 3 to 3-1/2 lbs of wood per hour, assuming 75% efficiency (most stoves nowadays are at least that).
And that would be only on the very coldest of days.

Sounds like an ideal setup.


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## Jimbob (Feb 21, 2011)

Alan Gage said:
			
		

> A nice graph showing the BTU output of a wood stove stove over an 8 hour burn would sure be helpful.
> 
> Any input appreciated.
> 
> Alan



The only input I can give you on this is a link to a thread where I track temps and time on a 13 lb. load of wood.
Wood is said to be 7500-8000 btu/lb.

Link:
https://www.hearth.com/econtent/index.php/forums/viewthread/70922/P22/#820508

The thread isn't scientific, but it gives you an idea. BTW, 13 lbs of wood will give you roughly the same amount of heat, whether you burn it in a 1.1 ftÂ³ stove, or a 3 ftÂ³ stove.


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## madison (Feb 21, 2011)

Like men talking about their "members" or bank accounts, divide by at least half to get the real number


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## wkpoor (Feb 21, 2011)

madison said:
			
		

> Like men talking about their "members" or bank accounts, divide by at least half to get the real number


I was thinking the same thing. Take any # divided in half and then you won't be disappointed.


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## thechimneysweep (Feb 22, 2011)

I've gotta weigh in here about the numbers being used in this thread for the available btu content in a pound of wood.  

In a laboratory, using an oxygen bomb calorimeter to burn bone-dry wood ( 0% moisture content ) in an atmosphere of pure oxygen, it is possible to extract 8660 btu's from a pound of wood. 

That number, known as the Absolute Heat Value, is sometimes used in scientific calculations, but, while useful in analyzing theoretical problems, the absolute fuel value of wood does not reflect real-world available heat. For one thing, the wood you burn in your stove is not dried to 0% moisture content: even a well-seasoned woodpile will contain about 20% water, which doesn't produce any heat in the fire. A 1-lb. stick of wood at 20% moisture content is only 80% wood, so it only contains about 6928 btu's of available heat energy (8660 x 80%). This is known as the High, or Theoretical Heat Value of fuel wood.

Even the Theoretical Heat Value must be adjusted, because 100% of that Heat Value is not available to be extracted to the room. The explanation is twofold:

1) A portion of the 6928 btu/lb must be used to boil away that 20% moisture content, as well as whatever humidity is present in the combustion air and the water that is created as a product of combustion.

2) Another portion must be "lost" up the chimney to establish the average 300Â° - 350Â° F flue temperature necessary to maintain an adequate updraft so the fire will burn properly.

I'll leave the math to Battenkiller here, but the bottom line is, once we subtract the heat value needed to boil off the water and the heat value needed to keep the chimney at 300Â° - 350Â° F, a pound of fuel wood at 20% moisture content actually only contains  about 6200 btus that are available to be delivered to the room. This is known as the Low, or Available Heat Value of fuel wood, and is the number most commonly used in firewood btu/cord charts.


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## BrowningBAR (Feb 22, 2011)

Battenkiller said:
			
		

> SolarAndWood said:
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The difference is, I think the Vig is 50k real world. I don't think that is Max BTU out put.


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## Alan Gage (Feb 22, 2011)

JimBob - I ran the calculations from your link and came up with similar numbers, about 16.5K BTU/hour. I did it quick at work so I didn't have all the exact numbers so it's not as accurate as it could be. I also wasn't quite sure how to do insulation. I plan on at least R60 in the attic but they largest choice they had was R40; so I chose R40 and R20. Had to do the same for the walls. 

This is the other online calculator I've been using: http://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

ResCheck is a bit more detail oriented than anything I've found online, wanting to know how the house is framed and it differentiates between cavity insulation and full coverage insulation, like exterior rigid foam. It's a fun bit of software that's easy to use and free to download from the Department of Energy. http://www.energycodes.gov/rescheck/download.stm

VC Burner - I've actually been using the Englander 13 in my double wide the past few years. It's certainly not a well insulated or well sealed house but the stove does a good job until the wind picks up or it drops to -5 or lower. My new house will actually be less square footage and a world apart when it comes to holding heat. I'm pretty sure the 13 would heat me right out of the place.

I'm really interested to see how things go next winter and you can be sure I'll be posting my results....hopefully it will be bragging. 

Alan


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## SolarAndWood (Feb 22, 2011)

Battenkiller said:
			
		

> SolarAndWood said:
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I'd buy it puts out twice the 2 cu ft stove it replaced.  It also reliably burns much lower.  If you are in front of the stove when its running wide open, you definitely feel the heat.  If you aren't directly in front of the stove, it is a non-issue.


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## Alan Gage (Feb 22, 2011)

Just for fun I punched up the numbers on my current house, the double wide. Had to make some educated guesses (have no idea of the R value of the old windows) and I think the house probably got the benefit of doubt overall since it's hard to quantify leakiness. Anyway, it's more than double (about 40K btu/hour) the numbers I'm coming up with for the new house.

Chimney Sweep - Thanks for the clarification.

Alan


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## webbie (Feb 22, 2011)

How about this simple calculator which uses the firebox size and type of stove to give a pretty good estimate of what to expect?:
https://www.hearth.com/econtent/index.php/articles/burn_time_calculator


choose the 1.1 cubic feet and the stove type and you will get some estimates.


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## thechimneysweep (Feb 22, 2011)

Or, how about a formula that takes into account the efficiency rating of your specific stove?

(( firebox size in cu. in.) x ( 0.015 ) x ( 6200 ) x ( stove efficiency )) / ( burn time )

To get the firebox size in cubic inches, we multipy the manufacturer's stated cubic foot measurement by 1728.

The 0.015 is the weight of the load per cubic inch. To get this number, we used an average of the top 60 species from our firewood comparison chart, and adjusted to compensate for airspace between pieces, using the ratio that a 128 cubic foot woodpile only contains about 85 cubic feet of wood.  This creates that we're not using the weight of X cu.ft. of wood, we're using the weight of the wood that will fit in a X cubic foot firebox.

The 6200 is the available BTU (heat) content per pound of fuelwood at 20% moisture content. 

For stove efficiency, we use the manufacturer's tested Low Heat Value rating.

For burn time we use 8 hours, although smaller numbers can be used for smaller fireboxes.

More at http://www.chimneysweeponline.com/wscomp8.htm


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## webbie (Feb 22, 2011)

Most of those numbers are in that calculator......roughly, of course, but so is anything related to this stuff. 

Heck, I failed Algebra.....


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## webbie (Feb 22, 2011)

Here are the rough assumptions in that calc:
function CalculateBTUs(fields)
        var Soft = 25;
        var Medium = 30;
        var Hard = 38;
        var ExtraHard = 44;
        var FireboxCorrectionFactor = 0.5; // correct for empty/wasted space in the firebox after loading
        var FireboxVolume = parseFloat(fields.FireboxVolume.value);
        var StoveEfficiency;
        switch(fields.Efficiency.value)
        {
            case 'Gasification Wood Boiler':
                StoveEfficiency = 0.75;
                break;
            case 'Newer EPA freestanding catalytic stove':
                StoveEfficiency = 0.7;
                break;
            case 'Newer EPA freestanding non-catalytic stove':
                StoveEfficiency = 0.63;
                break;
            case 'Newer EPA fireplace insert':
                StoveEfficiency = 0.55;
                break;
            case 'Older freestanding stove - airtight':
                StoveEfficiency = 0.48;
                break;
            default:
                StoveEfficiency = 0.4;
        var BTUsPerPound = 7000;
-------------------------------------------

the numbers above, all put together, are close enough for this type of thing.


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## RustyShackleford (Feb 22, 2011)

Alan Gage said:
			
		

> ... I'm coming up with a heat loss for the structure of between 17,000-20,000 BTU/hour at -20 degrees.


You mean outside temp of -20 and inside something reasonable (not a 20-degree temperature differential) ?   Wow, that's incredibly efficient, on the order of 200 BTU per hour per degree of temperature differential.   When I did the calc for my fairly-well insulated 1400 sq-ft place, I came up with something like 800.   Well done !


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## rkusek (Feb 22, 2011)

Alan Gage said:
			
		

> Thanks for the replies. I realize I'll have problems getting long burns from such a small firebox but I'm ok with that. If I have enough coals left over in the AM to light some small splits I'll be happy. I actually prefer a house cooler than most. 70 degrees and over I start getting uncomfortably warm.
> 
> BK - An average heat output of 1/3 or less from peak over a burn cycle would give me lots of room to play so that's good news. Even if it averaged 1/2 of peak output I should be sitting pretty.
> 
> ...




I'm not an expert but I've always heard cellulose with settle significantly over time.  The builder insisted on using some in the ceiling and we finally agreed on R19 fiberglass with R30 equivalent of cellulose on top.  I think I will regret not demanding R38 or higher fiberglass.  I actually installed R38 in my pole barn and I think the builder concerns with leakage between the batts was silly.  My walls were R19 (2x6) fiberglass.  Now I see Owens Corning has this ATTI CAT type.  Basically it is shredded fiberglass that blows in with a machine but it not supposed to settle and not as dusty to install.  My local mom & pop lumber yard is advertising it now too.  If you put cellulose in your wall cavities I think you can expect it to settle several feet over 10 years causing great heat loss.  Research this a little more, sounds like you have a great plan for a nice well insulated home that will be easy to heat with your woodstove.  I just wouldn't want you to be disappointed with the performance due to settling of the cellulose.


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## pyper (Feb 22, 2011)

huskers said:
			
		

> [
> 
> I'm not an expert but I've always heard cellulose with settle significantly over time.



Old cellulose definitely did. When I opened up my wall cavities the stuff was down at least 2 feet from the top plates.

That's not nearly as much of an issue in a ceiling application though, because there's much less thickness. Eight feet of cellulose will compress a lot more than one foot (due to gravity). In a ceiling, the cellulose will fill odd shaped spaces much better than fiberglass, too.

Supposedly the new cellulose, properly installed with a wet blower into open stud bays will not compress. I wonder though.


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## Alan Gage (Feb 22, 2011)

Great links to the stove output charts/calculator. I bet if I looked around on this site more than just in the forums I'd be surprised what I'd find. 

As for the cellulose I'll be doing wet blown in the wall cavities and it shouldn't have any settling issues. It's mixed with water and some sort of adhesive when it's applied so it fills in around everything very nicely and should stay put once it dries out. I'm sure there will be some settling in the ceiling but it sounds like it's not as bad as it used to be. I'll look more into the blown fiberglass but I don't know of anyone around here that's doing that.

Thanks,

Alan


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## Battenkiller (Mar 1, 2011)

thechimneysweep said:
			
		

> Or, how about a formula that takes into account the efficiency rating of your specific stove?
> 
> (( firebox size in cu. in.) x ( 0.015 ) x ( 6200 ) x ( stove efficiency )) / ( burn time )
> 
> ...




Spot on.  

Tom, I just want to say that your site contains the most accurate (IMHO) info on wood burning that I have encountered so far on the Internet.  Kudos to you and your staff for providing a virtual treasure trove of well-vetted facts and general info.  Keep up the good work.  There is lots a good info on Hearth.com, don't get me wrong, but there are some wacky notions as well... all part of any public forum where anyone can voice an opinion while having neither a technical background nor real-world experience as a prerequisite.


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## DickRussell (Mar 1, 2011)

Alan, if you get your house built as described, you'll have roughly R30 walls and that R60 ceiling. If you pay attention to air sealing all around the envelope, for a very tight house, you'll be pleasantly surprised at how slowly it cools down overnight. While your planned house is smaller than mine, your experience ought to be similar. Briefly, I am nearing completion on a superinsulated house. Walls are R40, attic floor is R60, windows are triple pane, basement walls R20, slab is R20. I have been heating it for now with a small stove, Quadrafire Millenium 2100, with output on the tag of 11-28K BTU/hr. The house design heat loss is 21,000 BTU/hr, for 4,000 sqft of conditioned space. It doesn't heat up or cool down very fast at all. With the outside temp getting down to zero for a while overnight, I lose a degree or two inside after the stove burns out around 12-1am. I don't rush over to restart it, as I know the temp won't have dropped drastically. But neither do I worry about the stove overheating the place during the day. The mass of the house absorbs the heat easily.

Getting the air sealing is very important, however. Heat loss due to air leakage costs more than many think. But for any amount of leakage you can easily calculate the heat loss due to it. A tight house also means you ought to have a small HRV to provide continuous makeup air for health and for keeping the inside humidity down. This seems strange to anyone who has no knowledge of or experience with superinsulated, tight houses. Also, tight means you really ought to design in an outside air duct for the stove, directly connected, as you would have the real possibility of backdrafting if someone turns on the range hood or dryer.


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## Alan Gage (Mar 2, 2011)

Dick- Great to hear from someone with a super insulated house. Did I read that right? You're heating 4000 sq. ft with that little stove? Or is there another heat source as well? Good to hear how little heat is being lost overnight. It's going to be a drastic change from what I have now. Waking up at least once in the middle of the night to refill the stove and still waking up to house temps in the 50's when it's -10 or colder outside. 

I was thinking of using an exhaust only system for the air exchange. Any thoughts on that? At first I'd planned on plumbing the stove to outside air but I've also heard of people using the stove as the air exchanger (with passive wall vents) in the winter (open windows in summer and kitchen/bath fans for shoulder seasons). Lots more research to do and decisions to make. 

What did you do to get R40 walls?

Alan


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## DickRussell (Mar 2, 2011)

Alan, you did read correctly. I am indeed able to heat that 4,000 sq.ft. of conditioned space with the little QuadraFire Millenium 2100. The numbers said it could, and the observed result confirms it. On some days it has had a little extra help, in the form of three dehumidifiers running to get rid of humidity from the plastering and painting. That might be another 1.5 KW (about 5,000 BTU/hr) or more at times, and some temporary lighting, all of which is heat released inside the building envelope. I've been finding that it's more effective to open one door downstairs an inch or so and another up for a few hours, with the stove running to offset the heat loss. Later I close the doors and keep the stove running to regain the degree or two lost during the venting. As I said, it's a long, slow climb back up. The primary heating system will be a two-ton Climatemaster Tranquility 27 heat pump. That won't be in for another few weeks. I needed to have the blower door test done before specifying the size. I got a better than hoped for result, 0.65 ACH at the standard 50 pascals depressurization. That would be something like 0.03 ACH "natural."

Above around R30 in a wall, the easiest way to achieve a high R wall is with a double frame. I have a 12" cavity, with dense-packed cellulose blown to a density upwards of 3.0 lb/cu.ft. That's over twice the natural settled density of the stuff, so it always wants to expand, avoiding settling over time. That double frame, with insulation between inner and outer studs, eliminates nearly all of the thermal bridging. The attic is a loose blow, and around 10% settling over time is factored into the amount, so that right now it could be slightly higher than R60. A small change in around 2,400 BTU/hr in my case won't be noticed. I do have good windows, triple pane, low-E, argon fill, fiberglass frame; U is around 0.17. All are fixed glass or casements. Double hungs don't perform as well in a cold climate.

Bear in mind that a superinsulated house is an extreme end of the scale, with an old, drafty, barely or uninsulated house at the other end. There is everything in between, and even among superinsulated houses there is a matter of scale. Four times the conditioned area equates to roughly twice in each direction, so there is surface/mass ratio to consider as well as level of insulation. While the smaller but equally well insulated house will have a lower absolute rate of heat loss, the thermal mass will be lower as well, and the rate of temperature drop inside could be greater. Between our size differences and different insulation, where my house may drop two degrees over a cold night without heat, yours could conceivably drop 3-4 degrees. That would be hard to calculate, since the temperature profiles won't ever be in steady state. You'll just have to wait and observe what happens. But I really don't think you'd have to wake up to a house in the 50s if you don't have an overnight burner. Still, you may want a quick warmup in the morning, with the main heating system.

With a tight house, you certainly will need a means to provide fresh air. You simply can't design in a certain amount of "leakiness." All you'll know is that it's worst in bitter cold and windy weather, and practically nil in mild, windless weather. Further, you'd have absolutely no control over it, other than by opening windows. Some have argued that exhaust via bathroom fans on a low setting, with makeup elsewhere via passive air inlets (such as by Aldes), are sufficient. Others argue that for the sake of limiting heat loss an HRV or ERV is appropriate. You really don't want to try to use the woodstove as an exhaust device, as the range hood or clothes dryer could easily backdraft the chimney if the stove air inlet is open to the room, even if you have passive air inlets. A side benefit to having outside air ducted directly to the stove is that when the fire burns out you won't have cold air flooding the room. That's one reason to make sure that the selected stove allows direct connection of an inlet air duct.

I haven't really participated in this forum until recently, although I've browsed the posts from time to time. Now, with the observations on the house and woodstove in hand, I thought I could offer a few things to say. I guess the big thing is that as a new house approaches the superinsulated end of the scale, old rules of thumb as to how big a stove is needed and even the idea that an overnight burner is essential don't apply. One really needs to have a good calculation of the house's heat loss at design conditions.

This isn't really the sort of forum to get much into building science, as it's more for stuff relating to wood burning equipment. If you haven't already done so yet, go over to Green Building Advisor (http://www.greenbuildingadvisor.com/) and Building Science (www.buildingscience.com). You can search there for all sorts of information on ways to achieve high energy efficiency in new construction.


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