To OAK or not to Oak

[Tonyray]

Stumbled across this a while back and wondered what others thought about it and if
it still holds true since many here are insulated up the whazoo and seem to feel they are keeping all heat from the stove inside the house with no problems of negative pressure.

From the 70's up through the early 90's home construction made significant leaps and bounds. In the 70's or earlier if you took all the air leaks in a home and added them together you would end up with approx. a 3' diameter hole in your wall! Todays construction however is so tight if added all the leaks it would amount to approx. a 3" diameter hole BIG difference. Also in the envelope of the home you have all these appliances taking air out of the home. Dryers, ventahoods, CH/A, and yes even the fireplace just to name a few and nothing is bringing air in so eventually you end up with a negative preassure in the home or a vaccumm if you will and the home will take a breath where ever it can. Because of this hearth designers and manufacturers have come up with outside combustion air kits to offset the negative preassure. sometimes its not enough to overcome it but does help in the stove efficency if the home is really tight.

 

[Ctcarl]

Good read

 

[Defiant]

Nice, my house was built in the mid 90's, no OAK for the XXV, straight out application and has worked great

 

[mikkeeh]

Find a neighbor that has an OAK. Hold your hand over it while the stove is running and take note of how much air is flowing. You are merely circulating outside air through the stove. Now .....imagine all the air that the OAK is moving, is HEATED air that it is sucking out of your house. This is your stove without an OAK. Now...while your stove is sucking your HEATED air out of the house..the house becomes a negative pressure zone...and sucks COLD air from outside in to replace it. Similar to leaving your bathroom exhaust fan all the time. Maybe its just me.....but it seems to be a no-brainer.

 

[P38X2]

Find a neighbor that has an OAK. Hold your hand over it while the stove is running and take note of how much air is flowing. You are merely circulating outside air through the stove. Now .....imagine all the air that the OAK is moving, is HEATED air that it is sucking out of your house. This is your stove without an OAK. Now...while your stove is sucking your HEATED air out of the house..the house becomes a negative pressure zone...and sucks COLD air from outside in to replace it. Similar to leaving your bathroom exhaust fan all the time. Maybe its just me.....but it seems to be a no-brainer.

Well stated.

It's not just you.

 

[Madcodger]

Nice, my house was built in the mid 90's, no OAK for the XXV, straight out application and has worked great

The flame of the stove is not affected by an OAK (or lack of it) if it can get air from somewhere. It really doesn't care whether you give it FREE outside air or heated (already paid for) air. So the fact that your stove "has worked great" is like saying your car will do 70 even with the parking brake on. Great engine, no doubt - but how's that gas mileage?

And for what it's worth, most contractors I've seen have about as much understanding of air sealing as they have of rocket science. Having a home built in the 90's - or even yesterday - comes nowhere near assuring a homeowner of a "tight" home unless a blower door test by a BPI or RESNET auditor is conducted. Yes, newer homes are moderately "tighter", often due to better materials. But unless they are used effectively, people would be shocked at what they are losing from air leaks.

 

[Tonyray]

The flame of the stove is not affected by an OAK (or lack of it) if it can get air from somewhere. It really doesn't care whether you give it FREE outside air or heated (already paid for) air. So the fact that your stove "has worked great" is like saying your car will do 70 even with the parking brake on. Great engine, no doubt - but how's that gas mileage?

And for what it's worth, most contractors I've seen have about as much understanding of air sealing as they have of rocket science. Having a home built in the 90's - or even yesterday - comes nowhere near assuring a homeowner of a "tight" home unless a blower door test by a BPI or RESNET auditor is conducted. Yes, newer homes are moderately "tighter", often due to better materials. But unless they are used effectively, people would be shocked at what they are losing from air leaks.

So the concensus here so far is having an OAK covers the bases without any guess work...

 

[newbieinCT]

Find a neighbor that has an OAK. Hold your hand over it while the stove is running and take note of how much air is flowing. You are merely circulating outside air through the stove. Now .....imagine all the air that the OAK is moving, is HEATED air that it is sucking out of your house. This is your stove without an OAK. Now...while your stove is sucking your HEATED air out of the house..the house becomes a negative pressure zone...and sucks COLD air from outside in to replace it. Similar to leaving your bathroom exhaust fan all the time. Maybe its just me.....but it seems to be a no-brainer.

very helpful! Thanks!
Just got an OAK intalled w/ my p61a today and I tried to explain to my dad why we got it and I muddled it up. I'll use this example next time we talk

 

[Harvey Schneider]

I like to make things visual.
If your stove uses 100 cfm for combustion and it pulls that from the house. That is a volume 10 feet by 10 feet by 60 feet every hour. Or visualize it as a 12 by 12.5 room with 8 foot ceilings, every two hours. All of that air is coming in as leaks and drafts from windows, door,outlets and improperly sealed seams.

 

[Bridgeman]

My house was built in 1988 and leaks a small amount of outside air at every window and door. My pellet stove, oil boiler and clothes dryer send heated outside at an alarming volume. I wonder what the savings in pellet use would be with an OAK? Everything is toasty and warm and I burn about a bag of pellets a day. Would the savings be worth the effort of drilling down through the brick hearth and 10' to the outside wall? With all the problems with ice and condensation I read on this site I have my doubts. I have access to a diamond core drill and am capable of getting it done. As an alternative, Is there a coaxial vent pipe I can run up the 8"X8" flue? The run to the top of the flue is about 18'. I currently run the exhaust gas out old school up the flue and the Harmon works great. I'm not inclined to fix a problem that does exist only to create a new ones like icing and restricted air flow leading to poor combustion.

 

[Defiant]

My house was built in 1988 and leaks a small amount of outside air at every window and door. My pellet stove, oil boiler and clothes dryer send heated outside at an alarming volume. I wonder what the savings in pellet use would be with an OAK? Everything is toasty and warm and I burn about a bag of pellets a day. Would the savings be worth the effort of drilling down through the brick hearth and 10' to the outside wall? With all the problems with ice and condensation I read on this site I have my doubts. I have access to a diamond core drill and am capable of getting it done. As an alternative, Is there a coaxial vent pipe I can run up the 8"X8" flue? The run to the top of the flue is about 18'. I currently run the exhaust gas out old school up the flue and the Harmon works great. I'm not inclined to fix a problem that does exist only to create a new ones like icing and restricted air flow leading to poor combustion.

The downside of OAK is pulling moisture from the outside through your stove, for your chimney application they make a termination cap that is easy to install. I have run my stoves for the past 16 yrs. without oak, maybe I need to do more research. I am also 50 ft. from a brackish water tidal river.

 

[Bridgeman]

So you suck cold air down the flue an some kind of trick set up to get through the thimble and into the intake on the stove?

 

[Harvey Schneider]

The downside of OAK is pulling moisture from the outside through your stove,

Please explain.
Cold outside air should have less moisture in it than warm, humidified inside air.

 

[Defiant]

My indoor humidity runs a consistent 30+%, you should be familiar with CT weather, last week during all that rain outside relative humidity was 98+%.

 

[Madcodger]

I give up... Do as you wish, ye doubters of OAK. OAK, no OAK, do whatever you've convinced yourself works. You can buy simple devices that measure humidity at a given temperature, but if you think the cold air is wetter, so be it. The moon can be made of cheese for you if you wish, and the snowflakes can be fairy tears.

This must be how my wife feels when she tries to teach me to cook. Seems as simple to her as falling off a log, and it just doesn't gel in my brain. The same is evidently true of physics for some.

 

[Greenhorne]

very helpful! Thanks!
Just got an OAK intalled w/ my p61a today and I tried to explain to my dad why we got it and I muddled it up. I'll use this example next time we talk

Can someone enlighten me why if an outside air kit makes a pellet stove somehow more efficient/ heat better/run better (not talking mobile home here).... why would there not be a similar setup recommended/widely used for a woodstove/wood boiler. I really can't see any benefit unless your home is so tight that when your wife farts at night while sleeping... the sudden increase in pressure airlocks the house and now you cant open the door in the morning without cracking a window first....

I know that is a bit much there but you get my point... I don't think it is necessary or really any benefit for an OAK in most homes. I have not seen anything beyond Mcguyver engineering experts to support the need or the actual benefit of an OAK.

Welcome any real study data that anyone has to support the need/benefit....

Thanks and not flaming just commenting on what I have not seen to be proved as fact

 

[BrotherBart]

Besides the long established fact that cooler, denser air makes for more complete combustion:

http://chimneysweeponline.com/hooa.htm

Wood stoves should have'em too. Wish I had the guts to bore the hole in the back of my fireplace.

 

[Mt Bob]

I like cold hard facts also,so I will pass one on-cold ouside air supplied to a building and heated up inside will lower the relative humidity inside.Not from me,from enginerring handbook.Also found if your inside humidity is too low you have air intrusion(leaks).

 

[BrotherBart]

And what no pellet stove manufacturer's lawyer will ever let them admit is that if the stove quits because of a power failure or whatever the dinky chimney most people use with them can easily turn into the intake and the stove intake become the exhaust and flood the joint with CO.

 

[GeHmTS]

Good luck on your data search, you'll need it. It's probably needed in the most extreme cases where other appliances may be pulling the same air as the stove and chocking the flame. For the most part, it's just a waste of $$$. I bought my stove, installed it myself through an existing chimney without OAK and my own vent pipes. My stove works fine with no issues and burns well. Every year I get my chimney cleaned, the sweeper tells me that I need a liner to get the BTUs out of the stove. Every year I politely decline. He also recommended that I have an OAK so it runs efficiently. Again I decline and mention the fire looks great. He finally recommended that I change the vent pipes to my stove. I finally told him that I will NOT have him return if he tries to sell me one more thing. He now does the chimney sweep only.

I have come to realize that when people find out that you're willing to spend $$$ on a stove, car, house, or whatever, they will push other unnecessary accessories on you. It's kind of like going to the dentist to get your teeth clean, and the dentist is asking you why you still have your wisdom teeth.

 

[Madcodger]

Can someone enlighten me why if an outside air kit makes a pellet stove somehow more efficient/ heat better/run better (not talking mobile home here).... why would there not be a similar setup recommended/widely used for a woodstove/wood boiler. I really can't see any benefit unless your home is so tight that when your wife farts at night while sleeping... the sudden increase in pressure airlocks the house and now you cant open the door in the morning without cracking a window first....

I know that is a bit much there but you get my point... I don't think it is necessary or really any benefit for an OAK in most homes. I have not seen anything beyond Mcguyver engineering experts to support the need or the actual benefit of an OAK.

Welcome any real study data that anyone has to support the need/benefit....

Thanks and not flaming just commenting on what I have not seen to be proved as fact

OK, I can't resist... Seriously? You want a study?? You have a combustion device... That requires air. That air is being actively pumped into the combustion chamber and almost immediately after the reaction we call fire occurs, it is actively pumped outside. PUMPED outside, because that's what a combustion blower does! Air comes in, combustion occurs, air goes out.

What temperature is that air going into the combustion chamber UNLESS it is being pulled in DIRECTLY from outside? How about ROOM temperature? And how did it become room temperature? Is there a magic supply of room temperature air reserved just for the stove? No, YOU HEATED IT to room temperature! And by actively pumping that air into the stove and back out, what you are doing is increasing the RATE of air changes that occur. For just this chain of events, It frankly doesn't matter whether your house is "tight" or drafty if a sufficient volume of cold air can be obtained (and if the stove burns, there is sufficient volume). Either way, you are accelerating the RATE at which you bring in cold air, heat it, and pump it back out.

Honestly, I am just at my wits end with people who can't grasp this. There is just no way to help you...

 

[thadd677]

This is my first season with a pellet stove and I didn't install an OAK. Now I have cold air getting pulled in through the vent by my cooktop in the kitchen, as well as other areas of the house. Next season I will definitely be installing an OAK.

 

[BrotherBart]

Ya ain't gonna believe what happens with a basement install of any stove without an OAK. Stack effect in the house kicks yer butt. While it pulls heat upstairs it sucks cold air in from everywhere in the basement.

 

[Greenhorne]

I like cold hard facts also,so I will pass one on-cold ouside air supplied to a building and heated up inside will lower the relative humidity inside.Not from me,from enginerring handbook.Also found if your inside humidity is too low you have air intrusion(leaks).

An actual engineer(one I have known for many years and trust) once told me houses... average houses refresh/leak about 60 % of their air every 15 minutes and we don't necessarily feel this because it is largely happening on the exterior margins of the home(attic, windows, doors, bathroom vent/vents, cookstove vents, etc.)... part of this is by design as the home needs to breathe and part is from inefficiencies. I have this weekend off so I will do some digging for some real data studies and not opinion based on opinion/generalities. I am not saying an OAK is completely wasted money spent as it is def a sure bet if you think you may have a tight home, but... I don't think it translates to guaranteed better efficiency, air quality, etc. in every case.

 

[Greenhorne]

Ya ain't gonna believe what happens with a basement install of any stove without an OAK. Stack effect in the house kicks yer butt. While it pulls heat upstairs it sucks cold air in from everywhere in the basement.

I think that would be very relevant, and also a bit of a different situation in that a basement is largely more air tight than an above ground structure.... in general.