# Practical Advantage to Fresh Air Intake for Pellet Stoves?



## taytowers (Nov 4, 2014)

Is there any _Practical_ Advantage to a Fresh Air Intake for Pellet Stoves?

I understand that Fire loves cold dense air...  and there is no advantage to burning warm room air and then shooting it up and out of the chimney.

But is there any one out there who can say that burning air fed from the outside has saved bags of pellets over the season?

The Reason why I ask is that my Castile Insert was installed into an existing old style heatilator metal firebox... with a traditional brick and clay liner chimney...  I was told that fresh air intake was not necessary, would not have any real world advantages as it would let cold air into the house along with mice, and would also be expensive to install...

If there is real world dollar savings...  I may install for next season.


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## TimfromMA (Nov 4, 2014)

I did my own OAK install for $50 in parts plus 2 hours labor. The increased comfort level of the house was worth the expense even if I cant quantify a monetary benefit.


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## bogieb (Nov 4, 2014)

The Harman in my basement was originally installed without the OAK. I got a lot of drafts on the main floor when the stove was cycling (none if this house is airtight by any means either). I installed the OAK myself and found that the drafts caused by cycling were no longer a problem (drafts during windy days, yes, stove cycling no). For your application, that might be the only advantage. And if you don't have any issues with drafts, or with other appliances starving for air (hot water heater), then you will probably be fine. Of course, I'm a newbie, so no expert, so YMMV.


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## taytowers (Nov 5, 2014)

I do notice a draft along the floor.  I may try using a fireplace insulation baffle blanket stuffed around the frame as a short term solution.  The fresh air then would be drawn down the existing brick chimney rather than around the frame.


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## Dhosh (Nov 6, 2014)

"would not have any real world advantages as it would let cold air into the house along with mice, and would also be expensive to install.."

It only lets cold are into the house, as your stove is in the house.  The OAK is to supply fresh outside air for the combustion chamber.  Once burned .. it's exhausted out the vent.  It's a closed system.   If you don't have an OAK, that combustion air has to come from somewhere ... which is from immediately around the stove.  Then THAT air is replaced with air sucked in from every leak you have on the outside of the house .. thereby sucking in the cold and making the extremities colder.  Not so much of what you want to accomplish. 

Mice? ... good .. let 'em crawl in and get smoked in the combustion chamber.  ... well, part of the OAK install process is to put a screen in/on the outside end so this doesn't happen.  But again .. it's a closed system.  They shouldn't be able to go anywhere.  The problem here is, you don't want them building a nest in that cozy pipe, and end up starving the fire because of it.  If mice are getting in around the OAK pipe, where it goes through the wall .. that would be a very poor/sloppy install job.

Expensive to install?  Probably not .. unless you get one of the pre-boxed kits.  I made mine out of PVC, and just found out that was a no-no ... so am now in the same boat .. kinda.  I'm not debating rather or not to install one ... just sourcing the parts to make it inexpensive .. yet proper.  I probably won't go the commercial kit route, but only to save a few $$.  

In your case, it might be a bit unsightly, but not only well worth it ... technically, I think it's 'required'.  

So, is your stove have it's vent just dump into the clay tile chimney .. or does it have a vent pipe that goes up, inside that liner?

I always thought the vent/combustion air kits would be the berries, as far as having a single install, but I'm not so sure as having the air intake that close to the exhaust would do the stove combustion any favors.


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## alternativeheat (Nov 6, 2014)

taytowers said:


> I do notice a draft along the floor.  I may try using a fireplace insulation baffle blanket stuffed around the frame as a short term solution.  The fresh air then would be drawn down the existing brick chimney rather than around the frame.


Where does your convection air enter the stove. And remember that yes combustion  air passes through the stove and out your stack but room air also travel back to the stove to be reheated. The difference here is that room air circulates but combustion air has to be replenished. Eventually returning room air should be warmer than it started out being as the rooms come up to temp. However combustion air is generally drawn from a cold drafty place I.E. leak. Combustion air causes a -pressure in the house, convection does not.


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## briansol (Nov 6, 2014)

The basic concept is this--

fire uses O2.
your house quickly runs out of it.

without an OAK, the stove draws in fresh air from all the nooks and crannies, creating cold drafts everywhere in the house. (negative pressure)
with an OAK, the stove has all the air it needs, and the room blower acts sorta like 'max ac', recirculating warm house air through the convection instead of trying to constantly fight with the cold air that keeps leaking in.


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## Lake Girl (Nov 6, 2014)

taytowers said:


> I do notice a draft along the floor.  I may try using a fireplace insulation baffle blanket stuffed around the frame as a short term solution.  The fresh air then would be drawn down the existing brick chimney rather than around the frame.



It sounds like your installer was either misinformed or lazy or both

Wouldn't that mean that you're pulling in exhaust as your "fresh air" (edit: unless you have a metal liner to the cap - not clear in your post and sounds like it just exhausts into the clay liner)?  Carbon monoxide   If you put a blanket around the frame, are you not also reducing the air to the convection fan?

Dhosh has it right that there is a screen on the air intake (also on the exhaust) to keep critters out year round.


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## OhioBurner© (Nov 6, 2014)

I doubt it will make any difference in actual heating, unless your house is so tight its starved for air. But pulling drafts through the wall could result in perceived difference if these drafts are nearby where you are. Overall I think it should be the same efficiency in heating your house.

A good instal would be well sealed, with screen, and insulated, so pretty much everything you were told was wrong. Putting one through brick could be a hassle and cost though, if thats what your talking about, your specific install could vary. In my case it was required by my stove manufacturer, and my house is very drafty so hopefully it will cut down on that. Kind of unsightly running across my living area though but thats not a biggie for me.


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## briansol (Nov 6, 2014)

I've had both non-oak for 4 years and oak for going on season 2 now, and the difference is night and day


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## snocross1985 (Nov 6, 2014)

My englander has had the OAK from day 1, but my harman was installed by the prior owners of our house (incorrectly, at that) and did not have an OAK. When the harman was running I could put my hand by the window trim and feel the cold air rushing in. Hooked up the OAK and that is gone. I find the difference to be night and day.


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## Dustin (Nov 6, 2014)

I had this debate myself, stove installed in front of a fully SS lined fireplace like yours. 

The fix, block off plate in the fireplace, short run of OAK pipe halfway up the chimney or less, and a couple of holes at top of the chimney. 

Found that here, many threads on it


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## taytowers (Nov 6, 2014)

_Dhosh:_ "So, is your stove have it's vent just dump into the clay tile chimney .. or does it have a vent pipe that goes up, inside that liner?"
_alternativeheat_  "Where does your convection air enter the stove"
_lake girl:_ "If you put a blanket around the frame, are you not also reducing the air to the convection fan?"

There is a flexible liner running down the chimney...  with a cap

As for where the air is being sucked into the burner and convection fan? You know what...  I don't know.   But am guessing that it is drawn in behind the frame.. ie inside the the fireplace...  So I will have to rethink closing off between the frame and the brick...  don't want to breath in old chimney air?

I will have to google the Castile Insert and see.


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## taytowers (Nov 6, 2014)

briansol said:


> with an OAK, the stove has all the air it needs, and the room blower acts sorta like 'max ac', recirculating warm house air





briansol said:


> I've had both non-oak for 4 years and oak for going on season 2 now, and the difference is night and day





snocross1985 said:


> I find the difference to be night and day.



Recirculating warm house air wile isolating outside air makes sense.  If the "night and day"  difference relates to cost savings.. then I will definitely have a Fresh Air Intake installed....

http://hearthnhome.com/downloads/installManuals/7022_122.pdf  page 16  shows how the fresh air needs to go down the chimney....  big job...  And the snow is already on the ground in this part of the world.


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## Dhosh (Nov 6, 2014)

I'm probably regurgitating known information, but here goes ...(Of course, if I'm wrong .. someone please chime in!)  

There are two fans .. one is the vent/exhaust/combustion fan.  This gets it's combustion air from the 2" intake on the back of the stove that (theoretically) is piped in from outside, gets burned, then exhausts out the 3" vent pipe.  

The other is the room air/circulation fan, that gets it's air just from around the fan (mostly inside the housing, I guess)... and blows out the front.  Mine has a row of tubes above the combustion chamber, that this air blows out of, into the room.

Both systems are isolated, effectively.


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## Dhosh (Nov 6, 2014)

Is there an outside cleanout to your old fireplace chimney ... or was all done from the fireplace itself?  If so, you might be able to use that hole and use the figure 15.1 method.


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## BrotherBart (Nov 6, 2014)

The minute you start a pellet stove you create negative pressure in the house. Not even close to ideal for complete combustion in the stove and best stove performance. Wood stoves get away with it, but a pellet stove because of the combustion blower volume of air.

Sure you can do it without an Oak. But don't carp about burning issues with the stove.


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## Dhosh (Nov 6, 2014)

I would run a fresh air pipe to a nearby blocked off, opened window (with a hole for the pipe, of course), before I'd let it breathe from the inside.

I was correct by another member on my use of PVC for this combustion air pipe, also, as it apparently isn't kosher.  If there was a downdraft, or something caused the fire to blow back into the fresh air intake (granted, albeit extremely unlikely .) ... it could be quite hot, and/or start a fire .. burning the pipe, and producing noxious fumes.  If you didn't have ANY pipe there, you would have the same flames/potential for fire, being blown right into your house.


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## TimfromMA (Nov 7, 2014)

If you check out the linked thread, I graph out my pellet usage pre and post OAK. i think the post OAK trend looks promising.

https://www.hearth.com/talk/index.php?threads/Pellet-Consumption-Graph.134185/


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## mrbennett726 (Nov 7, 2014)

A good friend of mine and I both run Harman P61A's purchased a few months apart. We also both live in old semi-updated farmhouses with less than ideal insulation. Last winter we installed the OAK Midway through the winter, and he noticed an immediate savings of almost 1/2 bag of pellets per day.


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## MarkF48 (Nov 7, 2014)

If you have a tight house a pellet stove may still get enough air for combustion, but consider if you start up a clothes dryer that exhausts to the outside, the clothes dryer will pull air from inside the house creating a negative pressure that will work against the pellet stove. If you have a different heating appliance such as a coal stove and a tight house, the negative pressure from something such as a dryer could conceivably draw CO from the coal stove into the house.


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## briansol (Nov 7, 2014)

The insert run is a bit trickier.   I had scott (@swilliamson on here) come out and install a 2nd run of intake pipe up the chimney to his custom 2-story cap set up (intake on 1st floor, exhaust on 2nd floor).  It certainly wasn't $50 like other's said they have done it for, but it was well worth the cost of having it done right, not a half run hack with punching holes


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## OhioBurner© (Nov 7, 2014)

mrbennett726 said:


> A good friend of mine and I both run Harman P61A's purchased a few months apart. We also both live in old semi-updated farmhouses with less than ideal insulation. Last winter we installed the OAK Midway through the winter, and he noticed an immediate savings of almost 1/2 bag of pellets per day.



I might be going out on a limb here but I'd say any measurable amount of savings is either coincidence, within standard deviation, or some other issue with the stove or perhaps changes in local weather. Looking at this from a scientific standpoint the difference in heating should be minute. I view it as more of a safety thing and to ensure a proper burn (is in the case where you had a drier or woodstove also going and competing for air). It'd be nice to see a study of this under controlled environment. I've been running my OAK now for about a week and if my feed rate is on one value it burns at a fairly constant rate. House temperature fluctuates greatly so its hard to discern any meaningful information. I certainly haven’t noticed any change big enough to shut my stove off more, or run it any lower, but temps vary so greatly in my house it would be impossible to detect small changes.


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## briansol (Nov 7, 2014)

From a scientific standpoint, if you're sucking in cold air to the house, you need more fuel to keep it warm.


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## taytowers (Nov 7, 2014)

BrotherBart said:


> Wood stoves get away with it, but a pellet stove because of the combustion blower volume of air


This coming from a 'staff member' seams like seasoned advice....  



mrbennett726 said:


> noticed an immediate savings of almost 1/2 bag of pellets per day


That would be close to a 50% increase in efficiency...  Hundreds of dollars there.



Dhosh said:


> Is there an outside cleanout to your old fireplace chimney


There is a clean-out leading to the basement...  but that is also the family room...  so I think I will have to run a second liner down the chimeny




OhioBurner© said:


> difference in heating should be minute


That's exactly what the installers said...  I was willing to pay extra... but in the end I took their advice... 


.


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## OhioBurner© (Nov 7, 2014)

briansol said:


> From a scientific standpoint, if you're sucking in cold air to the house, you need more fuel to keep it warm.



Yes, and that happens both with an OAK and without an OAK in about the same amount...


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## Dhosh (Nov 7, 2014)

Bummer on the clean-out ....was worth a shot, eh?


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## hyfire (Nov 7, 2014)

The cold air  from the OAK provides a denser mixture which may produce more btu's but its offset since you have colder air to heat  in the firebox so the output is basically  the same...


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## OhioBurner© (Nov 7, 2014)

Yeah hyfire is thinking along the same lines. But I guess I should elaborate what I was getting at earlier. Seems folks don't get much past the first step in the equation here, that no OAK is wasting your heated air up the chimney and with an OAK that that colder outside air is going to miraculously pass through your home without any effect to its surroundings. Just because your channelling the cold outside air directly via an OAK doesn't mean it has no effect on the temperature of the stove and your home. I mean combustion is what is heating your home right? That's in the stove right? It has a heat exchanger right? If you fed the stove with really hot air we'd expect to get slightly warmer temp out of the stove right? The heat exchanger is designed to transfer the thermal energy between the inside of the stove and your home. Now, the heat exchanger isn't 100% efficient, so some of that is going to go up the flu. I suppose just for ballpark numbers we could say that its 75-80% efficient which is what a lot of stove manufacturers claim. Of course the rest of the system isn't 100% insulated from your home either... you have the OAK run itself, and the venting. My OAK is long, exposing several square feet of ribbed aluminum 'heat sink' (typical 2" and 3" semi rigid aluminum duct). I insulated it with 1" fiberglass pipe wrap. Even with that insulation its not nearly as insulated as the rest of my house is to the outside. And then there is the several feet of duravent, which last I checked transferred quite a bit of heat still. So you have the transfer of thermal energy through the OAK itself, venting, stove wall and heat exchanger, and the slight reduction in combustion temps. Now without the OAK, your stove is combusting hotter air to start with, which should raise stove temps ever so slightly and again 75% of it or so will be transferred back. But your pulling air now through leaks in the house, which will slightly cool the home. The slightly hotter stove and slight cooling effect of the leaks should about balance. And the two scenarios should have similar average temps. I'd still say with an OAK that you'll have minutely better average temps. But not 50% gain in efficiency as some may claim. That's as silly as putting a cold air intake on your sports car and think it alone will gain you 200HP. Not going to happen (unless your house was tight enough your stove wasn't getting enough air to combust properly). I'd wager we're talking in the couple percent range. One thing that could really effect your perception of warmth is if your chairs, couches, and whatnot are close to walls or windows where the draft is coming in. Even if its balanced out by a very slightly warmer stove, in the area closer to the drafts will be cooler. So you may have more of a temperature gradient around the house. I for one have a hard enough time trying to circulate heat around the home, so I'd rather not have the greater differential between warmer stove and cooler walls, I'll take less drafts but slightly cooler stove. I mean my stove room already runs 75-80F and the next room through the doorway (family room) drops about 10-12 degrees. If you have a thermostat or thermometer too closer to a draft, its quite possible you'd think the house was colder, and if the stove was running on a remote thermostat, then it could use more fuel. But then the average temp of the house would actually be greater. I'm all for an OAK, and its required in my case anyhow, just don't expect its going to save you hundreds of dollars a year in pellets for the same average house temperature.


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## taytowers (Nov 8, 2014)

TimfromMA said:


> https://www.hearth.com/talk/index.php?threads/Pellet-Consumption-Graph.134185/


Great observations (and commitment)...   As others on that thread pointed out..  temperature variations year to year, and burning different pellet brands may swing the graph one way or the other...  but this has motivated me to repeat the experiment up here.  I have already noticed flame variation between different pellet manufactures...  so I'll settle on one and then keep track of the quantities over this season.


OhioBurner© said:


> One thing that could really effect your perception of warmth is if your chairs, couches, and whatnot are close to walls or windows where the draft is coming in


Even if there is no financial benefit...  I do perceive a draft around the living room sofa...  The purpose of the Castile was to improve the quality of heat along with saving money over my older electric hot water system.
Looks like the OAK will improve on the Quality by reducing drafts...  and may improve the Financials.


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## Noname (Nov 21, 2016)

briansol said:


> The insert run is a bit trickier.   I had scott (@swilliamson on here) come out and install a 2nd run of intake pipe up the chimney to his custom 2-story cap set up (intake on 1st floor, exhaust on 2nd floor).  It certainly wasn't $50 like other's said they have done it for, but it was well worth the cost of having it done right, not a half run hack with punching holes



I know this has been beat to death but here's my issue. Winslow pi40 insert, completely remodeled home but the old heatilator was capped off by the new roof so going up is not an option which is why the installer went out the double brick wall and up 5ft with the vent pipe. The insert burns fine but I see the sense in pulling in outside air. The Winslow is not a sealed oak setup but more just a flange, 2' inside diameter. There was a 3/4 inch hole drilled behind the stove where a gas line was at one time for a lp fireplace that I sealed, I measured the thickness of the wall and its approximately 16 inches thick. My question is if I drilled another hole and opened up the one that was there given that the insert itself is pretty sealed against the wall would the combustion fan draw the air? I'd of course screen off the outside but given the design of the oak intake would it matter if it was pulling air from a foot or so away versus spending a day drilling and chiseling so I can run a piece of liner up and basically lay it in a hole behind the fan?


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