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Outside Air Kits, Do you recommend them?

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by MountainStoveGuy, Jul 16, 2006.

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  1. webbie

    webbie Seasoned Moderator Staff Member

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    Well, it can all be one article and we can add/edit. First it could say what it is and why it might be used in mobile homes and such - then it could mention use for wood and pellet stoves.

    It could mentions the questions and the general conclusion of the experts (that most don't need it).

    It could eventually cover most of the bases.

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  2. elkimmeg

    elkimmeg Guest

    With all the discussions, I want to re state my stand. If inside air satisfies code and proper opperation and draft, I see no need for oak
    If an insert is spected only to function with outside air then outside aire is the only correct way to install it. If your home is modern and fairly tight possibly the optional outside air kit should be considered, if you have spillage, hard startups and draft issues.
    I look at outside air as supplemental. I also believe that the outside air feed should split to reflect presurization of prevailing winds that two openings are necessary on opposite sides of the home to achieve effectiveness.
  3. elkimmeg

    elkimmeg Guest

    Thanks thats exactly what I witnessed the one with the gages

    BTW these home earned a 5 star Home Energy Rating Certificate an effeciency rating of 89%. Some ranked the top rating 5 star plus 90 to 100%. Check out how they were rated goggle rem/rate July one New revisions were made for qualifying energy star homes.

    As things turned out today the builder and hvac contractor called me today to ask what I think they should do to make further improvements for the up commind revisions. My suggestion was to switch to Trane furnaces. They carry one of the highest Energy star ratings. Another unknown to most, they are made by American standard. Almost identicle to American standard but cheaper.

    To me any extra money spent for Trane is worth it. Simply put quality is worth the additional price. better than Carrier.
  4. begreen

    begreen Mooderator Staff Member

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    Trane is good equipment, though from the quotes I've been getting, the are currently marked up very highly in our area. I also like York's new Affinity 8T systems. They are as efficient and offer a better value while still having the same Copeland compressors and Johnson controls.
  5. elkimmeg

    elkimmeg Guest

    Yess Begreen You can subsitiute York for Trane maybe better bang fot the $$$ American Standard it great equipment. But for pricing. I will think of others
  6. Woodstove master

    Woodstove master New Member

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    I had to join this forum to post in this topic. It has been a huge debate as I see. I have done a tone of research about outside air for combustion and have a very good understanding of it and also how the sparks may have come out of the outside air vent.

    First I will give my learned and proven points of why outside air is a must. Some are in this post but a few are new.

    1. Out side air venting will provide the needed air supply to a stove much better than a tightly sealed home with inside air.

    Remember we are all here to get the most heat for our money. To heat efficiently we want all drafts sealed. As we do this we decrease the ability of the wood stove to get the required air needed for adequate combustion as we create a negative pressure in the home. When this happens we pull outside "cold" air into the home. I know of many people who have wood stoves and pellet stoves installed without the outside air kit. All of them complain about the heating ability of the unit and that the outside rooms are always cold.

    2. Outside air vent will not blow your freshly heated air up the chimney. When we use inside air for combustion we are using the air we just paid to heat. Now we are sending it outside! I want to keep the air I just heated with the stove in the house.

    3. Outside air is usually much colder than the inside air and thus will be higher in oxygen content. "Cold air is more dense and has a higher % in oxygen". This will help the fire burn more efficiently. The more oxygen you introduce into a fire the hotter it burns and it is more efficient. This will also reduce your chances of developing creosote and having a chimney fir by increasing the flue temperature above where creosote develops. Yes the air will be pre-heated some on its way thru the stove but will still be higher in oxygen content. I don't care how cold the inlet air is as it cannot decrease the temperature of an 800 degree fire in any significant level.

    4. When outside air is used, the stove then creates a natural positive pressure inside the home effectively sealing out any cold air from being able to enter through cracks, leaks in the homes exterior. "warm air has more pressure" When compared to outside cold air it is significant enough to make huge differences in heating capability.

    5. Humidity changes. An outside air vent will stop the home from dehumidifying. When inside air is used you are creating negative pressure pulling in cold "dry" outside air. Not only will it cause some health issues in some people but it can create a long term fire hazard. When we create the high temperatures we do near and especially above the stove it slowly over years will cause the flammable materials to dry over time at the cellular level eventually causing a fire. The material actually changes its composition lowering its flash point over time to a point that will ignite during normal operation of the stove. Most fires that start near wood stoves will not occur for 6 to 10 years after installation due to this effect. Most start in the ceiling around the area where the chimney goes through and or wall. I am A 16 year Firefighter / Paramedic. I must also mention that dry air seems much cooler than it would at normal humidity levels. When my stove had inside air I could not keep it above 20% to 30% humidity in my home even with a 12 gallon dual fan humidifier. Now I can save electricity of running that unit and the more humid air is more comfortable. When at normal humidity I can keep the house at 70 to 72 and be comfortable. With inside air and 25% humidity I had to keep the house at 85 to 90 to fell comfortable. This uses more fuel than necessary.

    I have used the same stove both ways. For the first year it was inside air. It did not heat well at all and used a lot of wood. I have a 1500 sq/ft mobile home that is well sealed. It did not matter, the negative pressure still pulls air from the outside rooms and they were very cold. You will use less wood by using outside air as you can see the advantages it gives. For the past 4 years I have used an out side air boot. The stove has almost doubled its heating and I use a third less wood. I had to make sur to seal the outside air kit 100% to make sure it will not draw any inside air. The kits are not built very well as far as how well they seal. I used 600 degree silicone sealant at all connections. Started a fire and then used an incense stick to check for leaks. If there were any leaks you would see the smoke enter the unit at the leak. I have a 100% sealed system. Now I get to keep all the air I heated, it is safer, more efficient, and I no longer have to use A huge humidifier as I did the first year as the home got so dry.

    I cannot tell enough of how important it is to use and outside air kit installed and sealed correctly. I have all info needed to settle this debate above and more if need be.

    in my next post i will go over the back drafting problem.
  7. Woodstove master

    Woodstove master New Member

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    By the way I have an Avalon wood Stove the "rainier". This is a high tech double walled stove.


    Now for the sparks from the outside air vent. I do not doubt for a minute that this actually did occur as i have seen it many times myself but it is not related to the outside air boot, it happens with inside air too. If this is a new stove then i must say that it must have been all the wrong circumstances at the same exact time to cause this. If an older stove with a poor deisign then one or both of the following.



    1. Stove design does not reduce the chance of back draft.

    2. Chimney is not high enough above the peak of the roof to stop the chance of a downdraft. Local codes here in New York state that the top of the chimney has to extend beyond the peak of the roof by no less that 2 feet.

    I had an old single wall wood stove that had a square hole in the back of it with a flap that controls air inlet. I have had on windy days sparks fly out this hole inside my home. This scared the heck out of me and started the research. This was such a poor design that you could look into the hole and see embers! A small downdraft because of a chimney that was lower that the peak of the roof and "bam!" sparks fly backwards. My research led me to extend the chimney by one 4 foot section bringing the top 28" above the peak of the roof. It was hard to start fires in this stove also. More on that below.

    A downdraft occurs in this situation when the wind blows from the opposite direction of the chimney from the other side of the roof to the side the chimney is on. When this happens the wind speeds up over the peak of the roof as it was passing over an airplane wing creating down force in this case. The wind hits the chimney at a pressure higher than the draft in the chimney and it runs in reverse.

    Having the top opening of the chimney terminate at least 24" above the peak of the roof will keep it above this downdraft preventing this from occurring, the wind will just blow by the base of the chimney.

    This 2 foot rule applies no matter how far you are from the peak of the roof. My girlfriend has a 45 degree angled roof on a two story home and the chimney was at the outer edge of the home. This made us have to make the chimney 16 ft tall and use cables to secure it to meet this rule and prevent a back draft. Safety first. OF course more expensive but better than placing a two foot section above the roof and having it downdraft and burn the house down.

    You can imagine the effect if both of the above were true in the same application it would be a recipe for disaster.

    I live on top of the largest hill in the area and the wind is always blowing. So bad at times during winter storms to blow shingles off the roof, siding off, and twice broke windows. Never once have I ever had any back draft of any kind with my proper installation. If the chimney is tall enough it should produce a draft more powerful then wind blowing by the opening providing it is at least 2 ft above the peak of the roof. This will also help you start the fires as an adequate draft will increase available oxygen to start the fire and keep it going. If your chimney is high enough above the peak of your roof and tall enough from the top of the stove you should get such a strong draft that it will actually increase with the wind blowing. I know this is true with my unit in the fact that it has to be turned down by the air inlet when the wind rips up as it increases the temperate of the fire by increasing the draft. I hear the wind blow and watch the air increase from the air inlet in front of the stove making the fire brighter. When wind blows by a properly installed chimney on a cold windy night / day it will actually create a vacuum at the opening if the chimney by the act of the wind blowing by and helping to increase the exit of the hot air. "cold hard science proves it as hot air rises. When given enough hight to do so can increase dramatically. Just like a gun. The longer the barrel, the more time the bullet has to increase its speed and energy. This goes the same for chimneys. My answer to any stove problems would be the hight of the chimney and or outside air.

    I have a newer stove also and agree to prior post that it is nearly impossible for a back draft to cause sparks to fly out the inlet. There is just too much space for it to have to travel to get out of the stove the wrong way. You would have to create a vacuum so strong that it would suck the coals from the bottom of the stove up 14" to the air wash inlet, through the screen in it down the sides, around a baffle then through the outside air boot.

    I say it is much safer to have the sparks have to fly through the extra space of the outside air inlet and deposit outside rather than not having the outside air boot and having the sparks land inside my house where they are much more likely to cause problems.

    I think It is settled! Outside air is a must. I have seen many chimney fires and fires caused by improperly installed chimneys or stove and no fires originating from a direct cause of an outside air boot. It just does not make sense.
  8. Woodstove master

    Woodstove master New Member

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    One quick note on sealing the outside air kits. You need not only seal the outside air boot but the old inside air inlet also as that will not longer be used. If you do not properly seal this, it will defeat the purpose of the outside air kit.

    My kit came with a plug that slid over the front air control nob and is supposed to seal the square inlet. Well it does not fit well at all. The hole for the nob shaft was 3 times too big creating a huge air leak. I used 600 degree silicone to seal around it. I then used a rubber gasket around the knob rod opening tight enough to still allow it to move and also seal the air entry.

    It does not end here. You must also check the bottom of the stove for air inlet leaks with a good strong fire going after the outside air boot is hooked up and the old inside air inlet sealed. Many stoves have breakouts in the bottom for other accessories like ash pans and blowers. You have to make sure that the breakout does not run along the path of the outside air or you will have a major leak. Mine had this exact problem and had to be sealed off. I ended up having to seal 6 different places around the front and bottom of the stove to ensure that it only gets its air from outside. Maybe this is why the efficiency of these outside air kits are being scrutinized. Installing them as per given directions will not do the job 100%. Without that how can we judge the effectiveness of the product?

    Remember to just start a good fire and light an incense stick. You want the fire to be burning well with the air inlet wide open to create a good draft and look for leaks. If there are leaks it will suck the smoke into it. Place the smoking tip of the stick around the front , bottom and outside air boot. You should only see the smoke rise not go into any vacuum leaks. If you find one seal it, find another, seal it till all leaks are found. Now you will have a true outside air boot / kit. P.S. Turn off the blower and or all fans you have in the area to have a calm area without drafts and watch where you breathe as not to blow the smoke all over the place.

    Any questions just ask.
  9. builderbob

    builderbob New Member

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    So, taking as gospel then that outside air accomplishes nothing, I apply that to the Travis Fireplace Xtrordinaire zc woodburner. It uses air cooled chimney, two 6 inch outside air ducts for shell cooling, and one 6 inch outside air duct for combustion. I conclude the Travis FPX sucking in all this outside air is sucking in a lot ot it for no good reason?

    Let the firebombs begin.

    BTB
  10. elkimmeg

    elkimmeg Guest

    First of all welcome to the hearth.

    I agree with a lot of what you are saying but there are points I will disagree with These points apply to two separate
    scenarios A newly tight home and an older more leaky home

    a tight home is the most beneficial for outside combustion air. The lower you stove is situated below the neutral presser plane the more benificial outside air becomes

    situations when competing appliances vi for the combustion air it is beneficial for combustion air coming from outside

    The next issue is health of inside air the tighter we build homes the less air changes occur. the level of stagnant inside air increases As we move to improve the insulation envelope,

    we have to deal with stagnant inside air issues .Years past mold never seemed to be a problem because homes were not as tight
    Now if my stove combustion air demand causes leakage infiltrations of fresh air, that may not be all that bad. ITS like we got so concentrated at leak prevention, that it caused other issues like indoor health. Now tight home rely on bath exhaust kitchen hood exhaust to try to make up fresh air changes. I here you about exhausting heated inside air, but that may not be a bad trade off for healthier air.

    Lets discuss the outside air kit It is usually installed in the most convient location to the appliance. No thought process to positive and negative air pressure effect caused by wind hitting the home Using the same principal for chimney height when wind hits a side of a home that is positive pressure zone. As it deflects around the home ,the reverse side becomes a negative pressure zone. Knowing cold air has a northern direction and warm air has a south direction the positive and negative sides of the home change with wind direction so where do you place the inlet?

    For one, you do not want to place in on the negative side but this is impossible to do when wind directions change
    Here is where the design fails the outside air dust should be teed and have two inlets on opposite sides of the home fitted with a one way flapper device to prevent negative pressure inside air escape or a combination of inside combustion air when the outside air location is in the negative pressure zone again the one way flap is engaged.

    Unfortunately, I mentioned many times no thought is given to the location of the outside air inlet location other than for convience.

    What you said about outside air is only partially true it is designed flawed

    Aslo it is true that if all combustion air is take from the outside there is less leakage in the home's envelope. Again this can be debated as whether it is better to have air changes and healthier indoor air. there is a trade off here as to which is the worst of evils.

    the leaky home one dies not need outside combustion air but maybe using a correctly designed one would prevent leakage. There has to be a balance here healthy inside air and leak prevention.

    You explained the chimney height conditions. There is nothing I can add to what you have said. It is well explained. This post runs 8 pages long and a year later we are still debating outside air. Some appliances require it, per the listing and manufacture specs. There is no debate from me where the appliance is tested and requires it. As an inspector I require it.

    I also look at the indoor volumes to determine sufficient combustion air is available and factor the current existing demands. I will require the additional inside air provisions or outside air provisions it the demand cannot be met completely within Cellars with multi combustion appliances are problematic locations one they are in the negative pressure zone and two other appliances may already use the existing volumes. No wonder n basement location stoves under preform. start adding playrooms and partitioning off boiler rooms and it creates all kinds of negative problems and increases health risk of back drafting appliances in the boiler room You bet I look at those situations and require corrective measures or I won't issue a permit for the new stove
  11. Todd

    Todd Minister of Fire

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    Welcome Wood stove master,
    I have seen this debate go back and forth for years and I still can't figure it out. I use a Condar air supply ventilator that is located about 3' away from my stove. Some people say it's just another open window, but being so close to the stove I think it supplies combustion air to the stove, eliminates negetive pressure in my basement caused by other appliances besides the stove, and helps with the stale air problem. I looked into the OAK for my stove and if I installed one it would ruin the looks of my hearth. As far as firewood consumtion, I think that's great your saving fuel, but I only go through 3 full cords burning 24/7 as it is, and I doubt I would go through less than that if I installed an OAK.

    On the other hand, I have a fireplace on my main level that use to really suck some air out of the house. It was so strong that it would pull air and smoke down through the other flue and out the basement stove. Not good, so I did modify it with some air tight doors and outside air through the ash dump. Problem solved. Now I can burn both if I want. With fireplaces I can see the advantage of an OAK, but woodstoves use much less air and I don't really know if it's an advantage.
  12. Highbeam

    Highbeam Minister of Fire

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    The OAK is required in my jurisdiction. It is really no problem to install and mine pulls air from a ventilated crawlspace so there are no wind currents. I don't think the plumbing on the hearth is ugly though it is certainly noticable.

    Attached Files:

  13. Woodstove master

    Woodstove master New Member

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    You all make very valid points that I mostly agree with. One thing I am not sure of is how much air these new stoves pull as one mentioned. I can only speak from experience and I have proved it in repairing several installations either myself or a recommendation after inspection. They all improved significantly.

    "So, taking as gospel then that outside air accomplishes nothing, I apply that to the Travis Fireplace Xtrordinaire zc woodburner. It uses air cooled chimney, two 6 inch outside air ducts for shell cooling, and one 6 inch outside air duct for combustion. I conclude the Travis FPX sucking in all this outside air is sucking in a lot ot it for no good reason?

    Let the firebombs begin.

    BTB "

    I love that! I thought I was the only one to use 6" outside air for shell cooling, I was wrong. I did not mention It on my last post as I did not think much would happen since the last post was a long time ago. This setup also saved me some cold outer rooms. I know this as I did the outside air for combustion one year and the air cooled shell with outside air a year later. Both increased the temp of the outer rooms and the temp of the main room the stove is in.

    As far as sucking it in for "no good reason"? Who cares, it comes from outside and goes through the chimney and out the top back to the outside.... You have a safer and cooler chimney to avoid house fires. The later is the benefit that does not have me worry if I have a fire in the stove when not home. The shell of my chimney can be touched with the bare hand this year. Before the outside air, I would need to call "911" after touching it. A major safety improvement and no more inside hot air to cool the shell.

    Great debate guys! I got more than I bargained for. I look forward to more reading / learning.
  14. elkimmeg

    elkimmeg Guest

    You are defeating the purpose of the chimney. We all know a warm chimney draws better. Cooling it down negates it ability to draw cooling it down, also aide the the development of creosote

    Pick you poison chimney fire from creosote or cooler = safer. Now if you need outside air to cool that chimney down to be safe, then I suggest there exist other problems, like too close to combustibles.

    You also failed to address the wind effect upon a home in relationship to the outside air inlet. Never addressed the one way flapper. You make statements but don't address issues I presented.

    I welcome good constructive debate we all can learn. Nobody has all the answers. This is not anti outside air, as I stated there are situations that require it . I just wish the deliver system was designed correctly and not for convience ,a system that addresses the down falls


    These stove are designed and the designing is an ever going process, where less is better. The longer heat remains in the stove the more is delivered to the living space, One way to hold heat in a stove is to reduce inlet air, less air exiting up the chimney. Really its not all that much. All modern appliances have reduced inlet or combustion air requirements. 150k Btu furnace high efficiency gas furnace only needs a 2.5" pvc combustion air inlet.

    This in not bring it on that is the wrong approach this is an educational discussion

    another point you did not address healthy inside air
  15. stoveguy2esw

    stoveguy2esw Minister of Fire

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    cooling a chimney is never a good thing, cooling the outer shell of a chimney to give closer clearances isnt necessarily a bad thing as long as the internal "working" part of the flue can be kept at a proper temperature. personally , i would not want an "air cooled" chimney it brings too much margin for error into play. intake air is going to vary in temperature and stack temps will as well, i'd hate to see what would happen in the extreme cold air flowing to cool and a lower stack temp from a small fire for example. puts too much on the operator to maintain large fires even when not needed.

    now outside COMBUSTION air is a different animal all together, there is absolutely no factor that is worsened by outside combustion air. cooler air is more oxygen dense creating more complete combustion, having OCA defeats negative pressure (which exists in all homes, not just new ones) and also doesnt waste heat from ejecting preheated air through the flue to outside. i would recommend it on any device that it could be equipped with it
  16. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    Edit: Asked a question and then found the answer.
  17. builderbob

    builderbob New Member

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    Darn good discussion, everyone!! Very informative.

    BTB
  18. WILDSOURDOUGH

    WILDSOURDOUGH New Member

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    Wife and I are on our second year of building "The Last Home" We built an ICF (Insulated Concrete Form) Basement-(stove and us living down here now- we hope to move upstairs by christmas but stove will stay down), SIP walls for the house and standard truss and R 38 roof with standing seam metal top. The house is TIGHT now and I am installing my Lopi Leyden with a 4" air intake from outside to the 3" air fitting on the stove bottom. I am doing this because-

    1. I have a Gas kitchen range, an outside venting microwave (vent hood kind) and 3 bathroom fans- all sucking air OUT>
    2. The manual talks about it, the laws in Washington state and Manufactured Homes require it. (maybe Canada too)
    3. This dissussion has convinced me that it's the right thing for me.

    May provide better combustion (or not), but at least it won't be drawing my heated air from the inside of the house out- kinda why fireplaces are not so efficent eh.
  19. kevinmoelk

    kevinmoelk New Member

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    Howdy everyone... I'm not going to read through 9 pages of responses, I'm a little late to the dance...

    In any case, let me just offer my own personal experience. I live in WA state, so an OAK is required. No big deal. I ran a 3" OAK to my stove and let me tell you it burns great. For experimental purposes I've disabled the OAK before and since I live in an older home you can feel the air leaking past windows and doors. When you open the door a big "whoosh" of air will come in as the pressure equalizes in the home. With the OAK in place, these problems do not exist. Suffice it to say, though I'll be leaving WA state next year to live in Maine, I will install and use an OAK there too.

    -Kevin
  20. elkimmeg

    elkimmeg Guest

    I have been thinking about another point said Again the original point is true but not applied to wood stove combustion
    cooler out side air contains more oxygen a true statement no disputing that.

    but in the case or wood stove burning cool is not necessarily better . In order to achieve secondary combustion the stove temps inside the fire box has to
    exceed 1000 degrees Combustion air outside fed or from with in many stoves channel it around the fire box super heating it. Cool air coming out the secondary air tube would not promote secondary burn but retard it cool air entering the cat combustor chamber or secondary combustion chamber would prevent this secondary combustion from occurring

    for secondary combustion these stoves channel that air around the firebox to super heating to ignite secondary combustion. In this case ,using heated room air would require less heating to temps. It would also not need to dissipate additional heat from the fire box to heat it There is no advantage for secondary combustion using cold outside air including the extra oxygen.
  21. tradergordo

    tradergordo Minister of Fire

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    "Woodstove master", first, welcome to the forum, I appreciate your contribution. But most of your arguments (possibly all of them?) have been debunked. I think Elk hit on the important things already - indoor air quality is #1 for me - and your setup is downright awful - a super tight home with absolutely no ventilation is a recipe for problems. Couple no ventilation with high humidity, and you have even more potential for problems.

    As for the "back draft" issue - as Elk mentioned - you did not address the problem at all in your comments - chimney height is irrelevant to the wind induced negative pressure problems related to OAKs (especially a SEALED OAK like you have). Although I think at this time this issue has to be considered somewhat irrelevant because thus far no one has been able to produce any documented fires that resulted from such a configuration...

    Several (possibly all of them now?) stove manufacturers advise against sealed outside air connections. Most outside air flanges on new stoves are engineered to prevent a seal (sounds like yours was too!). Why do the manufacturers not recommend sealed OAKs? As a firefighter, do you really think its a good idea for people to be modifying their stoves? Why do all of the owner's manuals warn against modifying the stove?

    I haven't searched all of the manufacturers, but here is a statement from Jøtul on this subject:

    "Jøtul North America ONLY requires the use of the outside air kit where required by local code and does NOT promote or recommend the use of a directly connected outside air source. All ducting must be non-combustible and clearances to combustible materials must be maintained."


    Do you claim to know more than the industry professionals who build our stoves??

    (I also find it interesting that from what I've seen, almost NO ONE who uses an OAK follows Jøtul's advice in maintaining clearances on their OAK ducting - typically people use super thin dryer vent type material with no special consideration for clearances to combustibles. But as I already said, I think this is a minor and possibly irrelevant point)

    p.s. Very few natural gas furnaces use OAKs, and they require SUBSTANTIALLY more air than your woodstove. Why do you think this is the case?
  22. Jags

    Jags Moderate Moderator Staff Member

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    Elk, I think you are giving too much credit for a 40 to 80 degree temp. differential (meaning outside air is 40 to 80 degrees colder than inside air). When looking at the big picture of 1000 degrees for secondary combustion, I really doubt that the difference in temps from outside to inside will be the deciding factor in the reburn process. Does it make a difference? Sure, if you are a piece of electronic monitoring equipment, but probably not to us humans. Possibly the temp difference would cause the end of "fire" cool down to happen a little sooner, but heck, if your gonna be heating, its time to throw another log on anyhow. Just my $.04.
  23. elkimmeg

    elkimmeg Guest

    Jags I agree but the point is that inside air was at least equal for secondary burning as outside air

    Don't get me wrong outside air has a place and valid use. It is not one size fits all situation for requirement.

    Like I said this is to be an educational debate for me. the rest, and woodstove master ,who resurrected this debate

    Woodstove master put a lot of though into his post make some valid points but is now finding there are other valid concerns.

    what happens if the OAK is on the leeward side of a home with decent breeze the negative pressure side it is possible to draw from that stove to the outside it could actually starve the stove

    that is why I suggested two opening on opposite sides with the one way flapper and that is the reason it has to be non combustiable and clearance distances required incase negative pressure draws combustion air out of the stove
  24. Jags

    Jags Moderate Moderator Staff Member

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    Agreed, this has been a good discussion.
  25. tradergordo

    tradergordo Minister of Fire

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    Phoenixville, PA
    The stove will use the same amount of oxygen for a given burn (heat output) regardless of the air temp so the "density of oxygen" in the air is irrelevant. Think about it this way, lets say you hooked up a tank of pure oxygen to your sealed outside air flange. Wouldn't you just be forced to turn your air control all the way down to control the fire (assuming it could be controlled)?

    You control the burn with your air control, it doesn't matter how oxygen dense the incoming air is because you will adjust for it either way so that you get the same heat output. Besides, the cold air immediately heats up and is then no more oxygen dense than the room air, I think people vastly overestimate this "oxygen density" difference between cold and warm air.
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