Cons to having an O.A.K.

[Hogwildz]

Heya Gordo,
Hows things down south there?
I have a wreck to look at in Bechtelsville tomorrow. Close to being near my old stomping grounds, kinda anyways.
Still have any of those Walnut seeds?

 

[CO2Neutral]

20 CFM is what my old Century Stove used (I measured it with a blower door on a calm day). I do this work for a living so I know I did it right. Anyhow, I generally see more houses with air quality issues from being too tight and the little evacuation of 10-40 cfm per minute shouldn't scare anyone especially since it brings fresh air in from the outside helps keep the humans inside healthy.

That's exactly how I feel. The only counter argument so far is basically, "well OK, but if you want ventilation you can install an expensive air exchange system". That's fine with me, in that case go ahead and install both an OAK and an expensive air exchanger for your house (complete with constant power drain requirements and higher electric bills). While I'm fine with this idea if that's what you want to do, I'd personally rather just let the stove be my "free" air exchanger. I think this topic has been beaten to death, but I just want to emphasize that if you do use an OAK you should definitely also be using an air exchanger in your home.

Agreed --> I see way too many sick homes due to lack of ventillation. My mother leaves her kitchen window cracked even when the temperature is -20C outside.

My house is too tight and I have a humidex in the basement which is an exhaust only system. I had to buy a passive air vent to allow air to be pulled in from the outside rather than down my chimney (even with the stove door closed I could smell smoke when it is turned off since the chimney is the only hole in my house ((no bathroom fans yet))). At startup I would get smoke spillage unless I cracked a window or turned the humidex off. An OAK would help this but a passive air system would be better in balancing the whole house negative pressure due to my exhaust only device and the high winds I have in PEI.

But if I find I still need an OAK I'll definetely put one in but I'll see how my passive air plays out (and I'll test it with my blower door to see how my pressure in the house behaves). I'm also glad I realized how negatively pressurized the house was and having some fresh air through the new hole in the wall will be a bonus.

 

[tradergordo]

Heya Gordo,
Hows things down south there?
I have a wreck to look at in Bechtelsville tomorrow. Close to being near my old stomping grounds, kinda anyways.
Still have any of those Walnut seeds?

Ready for winter. Built a nice new woodshed over the summer. Used real nice 30 year architectural shingles on the roof that I somehow got from Home Depot a while back for $1/pallet crazy clearance.

I probably still have viable black locust seeds if anyone wants some...

 

[Rockey]

This will be my first year with an oak on my insert. No ugly ductwork to see and fairly simple to make. I am more interested in trying to keep the humidity up in the house. No idea if it will work but I will find out. Just the thought of the intake air not having to pass through my house and remove heat was inspiration enough.

 

[laynes69]

I'll jump in here. I have a 150+ year old victorian. Its well insulated in the walls, but at the base of the foundation there are some good leaks I can never seem to fix. We get a lot of cold drafts in the basement. With my new furnace its basically a woodstove with a air jacket. I have debated trying an OAK. The furnace doesn't use much air, but that baro does. We also have no returns in the basement so there are no negative pressures there. Would a OAK help slow the drafts due to the baro pulling air? What I was afraid of is the baro pulling freezing air through the OAK cooling the flue too much.

 

[CO2Neutral]

FWIW, and disregard any of this if it doesn't apply to you: being in the energy business I would recommend sealing up your basement as best you can (you might need a blower door test -- spray foam on the sill plate/wall cracks is your best option although can be $$) -- definetely have it insulated (depending on your above ground portion of basement wall you will lose 20-35% of overall heat through the basement. Once you are tight enough in the basement and it's comfortable down there (loose description but I'm trying to suggest you get the drafts down to a low level) then I would consider an OAK. Basically I wouldn't put an OAK in if it's as draft as you say unless it's a really easy job and you are in the mood to experiment. I like OAKs and passive air vents because we can control the airflow better rather than letting the walls be whistling, etc. Good luck.

 

[North of 60]

The biggest positive difference I noticed was controlling my humidity levels by having an OAK. ALSO...
Having a leaky home to me would actually require an OAK even more. Especially in a cold climate due to that you are controlling where that cold air is coming in from. It will help eliminate the nasty drafts where your water pipes may freeze. In a very cold climate it doesn't take much. But again Im a guy who burns pine on the coldest days spruce and poplar in the shoulder season. My 2 cents.

 

[CO2Neutral]

Good points -- I've never lived in a "leaky"basement and seen the effects an OAK would have so my opinion was only based on my current house. My house is so tight I actually use/like/"need" the house air evacuated by the stove to get to a 50-55% humidity level but I'm right on the maritime ocean here.... It's funny, I thought I had the house figured out until I upgraded my stove to a bigger model. In a month's time I may an OAK installed so I'll never say never.

Burnin' spruce and pine tonight!

 

[LLigetfa]

Personally, I think humidity control should be left to a HRV. Sending humidity up the flue could create situations where you might have more condensation in the flue. They say that the amount of air that can leak out through one electrical outlet may condense as much as 5 gallons of water into the wall stud cavity over the course of the Winter. I don't think a fire would benefit from more humidity either.

There are more cons than pros to an OAK but if you address the cons, the pros will have it.

 

[tradergordo]

Not to continue beating the dead horse, but if installing an OAK causes your house humidity levels to go up significantly, its a SURE SIGN that you are not getting adequate ventilation in your home, which once again, is BAD for your health. This is a problem and not a positive attribute for OAKs!

 

[North of 60]

Not to continue beating the dead horse, but if installing an OAK causes your house humidity levels to go up significantly, its a SURE SIGN that you are not getting adequate ventilation in your home, which once again, is BAD for your health. This is a problem and not a positive attribute for OAKs!

Your flogging a dead horse with my cold climate. We get down to 15% RH here. When I run the ELECT Humidifier @16 cents a KW and I am able to maintain 30% with Unit on low. Without The OAK Unit will be on High to maintain 25%. Thats a diff of $40min, a month. When you are humidifying and the cold air is being brought in around windows and doors. It will condense and ice up on those extremities. At 1" or more thick in the bowels of winter. I don't see it any more with the OAK. This horse is alive and Kicking!
N of 60

 

[tradergordo]

Your flogging a dead horse with my cold climate. We get down to 15% RH here. When I run the ELECT Humidifier @16 cents a KW and I am able to maintain 30% with Unit on low. Without The OAK Unit will be on High to maintain 25%. Thats a diff of $40min, a month. When you are humidifying and the cold air is being brought in around windows and doors. It will condense and ice up on those extremities. At 1" or more thick in the bowels of winter. I don't see it any more with the OAK. This horse is alive and Kicking!
N of 60

I'm not sure what you are disagreeing with. You state the obvious - that your house is getting less ventillation with the OAK. Perhaps you are getting adaqute ventilation anyway, because you still have to run a humidfier which is a sign that the super dry outdoor air is getting in and drying out your indoor air?

 

[Highbeam]

Ventilation of the living space is overrated. Even if it isn't, ventilation is a central HVAC system issue and not a stove issue.

 

[tradergordo]

Ventilation of the living space is overrated. Even if it isn't, ventilation is a central HVAC system issue and not a stove issue.

I'm not sure if you are joking (sarcastic) or not? But if you were serious, you are forgetting that the stove IS THE CENTRAL HVAC SYSTEM for almost every real wood burner.

 

[bjkjoseph]

i posted a comment last year on this.if the only appliance you have pushing air out of your house is the wood stove you might not need one.but in most cases people are using the boiler,then you got your dryer,then you have bathroom fans,or maybe a hot water heater then you are running into risking your life with c02.that's why they came into being for safety reasons that's it.they have been making them for boilers for many years.it happens all the time even without wood stoves in the house.just seen it again,people moved in down the block.c02 detector went off.fd responded c02 off the meter, it would have killed his whole family.he does not have a wood stove and no faulty appliances,just the dryer and the boiler and not enough outside air.in new york we have building codes that state you must have fresh air for the boiler room.so i like the idea of the oak but if you dont have one just make sure you have make up air for the air leaving the house.

 

[tradergordo]

i posted a comment last year on this.if the only appliance you have pushing air out of your house is the wood stove you might not need one.but in most cases people are using the boiler,then you got your dryer,then you have bathroom fans,or maybe a hot water heater then you are running into risking your life with c02.that's why they came into being for safety reasons that's it.they have been making them for boilers for many years.it happens all the time even without wood stoves in the house.just seen it again,people moved in down the block.c02 detector went off.fd responded c02 off the meter, it would have killed his whole family.he does not have a wood stove and no faulty appliances,just the dryer and the boiler and not enough outside air.in new york we have building codes that state you must have fresh air for the boiler room.so i like the idea of the oak but if you dont have one just make sure you have make up air for the air leaving the house.

It sounds to me like you have things mixed up, but maybe you can explain what you mean. Not having OAK means MORE not LESS living space air exchange, which means lower chance of carbon monoxide (which is CO, not CO2) buildup or buildup of anything else that might not be good for you (including CO2 and particulate matter).

You can't rely on bathroom fans, hot water heaters, or dryers, for fresh air exchange, because they are all intermittent devices with low actual running time on any given day. An OAK is not an indoor air exchanger.

 

[bjkjoseph]

its very simple,this is how it happens say you have your dryer running,and maybe you have the exhaust for your range on,and then the boiler kicks on,if you have a tightly sealed home the dryer and the range could pull the exhaust from the boiler into your living area.when an appliance like a wood stove has its own o.a.k. it will not compete with other appliances for air.

 

[LLigetfa]

Not having OAK means MORE not LESS living space air exchange, which means lower chance of carbon monoxide...

That's got to be the most twisted logic I've ever heard. Too much air draw can reverse a water heater or furnace exhaust vent that under normal conditions would not be dumping any CO into the living space. The absurd notion that reversing the draft and then diluting it should win you a nomination for a Darwin award.

 

[Highbeam]

Excellent. I think that too much value is being given to air exchange here. Especially the random uncontrolled exchange from a woodstove that is not connected to an OAK. I see this as a negative (the purpose of the whole thread) and some see this uncontrolled air exchange as a positive. If you really want uncontrolled air exchange and value letting the outside air into your home then open a window, don't botch up a sealed combustion appliance to try and use it for something it was never intended to do.

 

[branchburner]

For a given house it seems it would make sense to first estimate whole-house air exchanges independent of any appliances, and then factor the appliances and potential pros and cons of an OAK. To some degree you'll have random, uncontrolled exchange with or without a stove, with or without an OAK. Not having an OAK may make that worse, but not in a way that's entirely unpredictable. I am sure there are both some strong pros and cons in specific situations, but only rarely. I don't see how you can generalize OAK as either good or bad. I do see how you can generalize OAK as irrelevant 90% of the time.

But isn't the idea of an OAK is to have constant, controlled combustion air, and does real-world experience show that to be the case? If the supply isn't constant, then how much of a con is that, and do the pros outweigh it:
GHETTONTHEBALL: "... why do oak on stove considering the wind fluctuations will affect the constancy of the combustion air"?

 

[Highbeam]

Crawlspaces don't have windows. Most, like mine, are permanently ventilated. They are not living space.

 

[10-cc]

I guess if you use a Heat Exchanger you do not have to wary about OAK or/and negative pressure.

 

[branchburner]

But isn't the idea of an OAK is to have constant, controlled combustion air, and does real-world experience show that to be the case? If the supply isn't constant, then how much of a con is that, and do the pros outweigh it:
GHETTONTHEBALL: "... why do oak on stove considering the wind fluctuations will affect the constancy of the combustion air"?

wind blowing on oak side of house will pressurize the oak & feed more combustion air. from opposite side itll suck on the oak & depressurize it= less combustion air.wind flux via direction & intensity will result in combustion air fluctuations as it feeds the stove,eh?

Right, but how much will that effect stove performance? And again, can the benefits of an OAK outweigh that problem?

 

[tradergordo]

Not having OAK means MORE not LESS living space air exchange, which means lower chance of carbon monoxide...

That's got to be the most twisted logic I've ever heard. Too much air draw can reverse a water heater or furnace exhaust vent that under normal conditions would not be dumping any CO into the living space. The absurd notion that reversing the draft and then diluting it should win you a nomination for a Darwin award.

So show me some real data (as opposed to speculation) that a woodstove in a typical house is likely to reverse the draft on a water heater or furnace exhaust vent.

Others are talking about furnaces in large buildings - this obviously has much higher air requirements than a typical house, it makes sense to require an OAK in such a situation. Again, a woodstove uses very little air. Wood stoves with gasketed doors consume in the range of 10 - 25 cubic feet per minute of air, which is a tiny amount of air, much less than an oil or natural gas furnace. It is also a very small amount of air compared to the natural leakage rate of houses. Building scientists say that the air in a house must be exchanged at least every three hours, or one-third of an airchange per hour, to control moisture from cooking and washing and to manage odors. One third of an air change in a 1500 square foot house is 4000 cubic feet, or 66 cfm. Note that this is the absolute minimum air change for healthy living and that most houses older than 20 years have natural leakage rates far higher than this in winter. So the air consumption of a wood stove is a tiny part of a much larger exchange of air between the house and outdoors.

Unless you can actually measure negative pressure in your home when the stove is running, or otherwise observe some negative result like an appliance vent reverse flowing, then there is no reason to use an OAK.

SEE:
http://www.woodheat.org/outdoorair/outdoorairmyth.htm

 

[Highbeam]

"Building scientists say that the air in a house must be exchanged at least every three hours, or one-third of an airchange per hour, to control moisture from cooking and washing and to manage odors."

This is the problem. That's like saying that, "traffic engineers say you must drive 5 mph for best safety" or the tree huggers saying that you musn't cut a single stem. Buying into that 66cfm requirement will cause you to all kinds of crazy things like using your woodstove for fresh air exchange.