To OAK or not to OAK? That is the question.

[VCBurner]

OK, here we go again. I'm trying to decide weather or not to instal an outside air kit.

I've been thinking of feeding my stove some outside air. This stove is in the basement. I noticed the stove was getting a lot of its air supply from a garage in a walk out portion of the basement. This garage was by far the coldest room in the house. It was poorly insulated and leaked around the overhead garage door. Last week I insulated the garage door and eliminated any air leaks. I've noticed the stove now gets a lot of its air supply from the upstairs (ground floor.) This makes the colder air upstairs be replaced by warmer air.

It makes sense to use an OAK not only for the air quality inside the house, but it would seem cost effective not to waste heated indoor air to feed a fire. In some stove installations an outside air kit is not only necessary but mandatory.

As a result of a recent thread response I started to think of some negative effects:
1. Another member posted about his negative experience with an OAK on his basement stove. His stove was burning cooler and shorter as a result of the rushing cold air.
2. The air circulation may lessen as a result of an OAK installation. The warm air may move slower to the upstairs. Instead of being pulled upstairs because of the negative pressure created by the stove sucking the cold air from up there.

I've noticed, as with all stove related questions, the answer depends on the particular home/stove. It all seems to be on a trial and error basis. What works for you may not work for someone else. However I'd like to know from some OAK users what your particular experience was with this system. It seemed almost fail safe until the recent response. I should have known it was too good to be true. It never seems to be a black or white. With the stove heating world there's always a grey area...

 

[tradergordo]

I don't know why you need a new thread for this, just use the forum search, its been beaten to death, I don't think any of the veterans want to do this again...

But I have to comment on one thing you said:

It makes sense to use an OAK not only for the air quality inside the house

This is wrong. Indoor air quality suffers from using an OAK, the reason is that without the OAK your home's natural air exchange (ventilation) is higher. Often installers who recommend OAKS also strongly recommend installing a separate air exchanger for your home. Personally I think if you go with an OAK some kind of house air exchanger should almost be required.

Its worth noting that some jurisdictions that formerly required OAKs have since realized that the requirement didn't make sense, and they have removed these rules.

 

[VCBurner]

I don't know why you need a new thread for this, just use the forum search, its been beaten to death, I don't think any of the veterans want to do this again...

But I have to comment on one thing you said:

It makes sense to use an OAK not only for the air quality inside the house

This is wrong. Indoor air quality suffers from using an OAK, the reason is that without the OAK your home's natural air exchange (ventilation) is higher. Often installers who recommend OAKS also strongly recommend installing a separate air exchanger for your home. Personally I think if you go with an OAK some kind of house air exchanger should almost be required.

Its worth noting that some jurisdictions that formerly required OAKs have since realized that the requirement didn't make sense, and they have removed these rules.

"Hey Gordo, if you don't want to comment, don't comment!! I read a lot of your posts including videos, etc... I found some of the info very helpfull. But the thread is there for all who want to read it and respond to it so if you don't care to then don't. Good night sir!"

 

[LLigetfa]

IMHO a stove would have to be running poorly to begin with for an OAK to make it worse. The reasoning of consuming heated indoor air versus outdoor air is unfounded. The cold outside air also needs to be heated inside the stove so it's a wash. The difference is with comfort factor. Consuming inside air means that cold air will have to replace it usually resulting in uncomfortable drafts or a danger of CO due to another flue reversing.

It is better for the flue to draw dry outdoor air than humid indoor air that can condense in the flue. If you don't have an OAK the more frequent air changes will increase dryness.

An OAK is not a cure for bad draft or stack effect induced negative pressure. IMHO an OAK can make a bad thing worse. If there is a pressure deficit, the OAK can push smoke into the house. The pressure of the outside air can supercharge a fire and if the stove cannot regulate it you can have a runaway situation. I had that problem but I solved it by controlling the zipper air.

Another problem I had was my flue constantly drawing heat out of the house when the stove was not in use and the cold air from the OAK turning my stove all frosty. I added a positive shutoff to the OAK to stop the air flow.

All that said, I would still install an OAK if I didn't already have one.

 

[VCBurner]

IMHO a stove would have to be running poorly to begin with for an OAK to make it worse. The reasoning of consuming heated indoor air versus outdoor air is unfounded. The cold outside air also needs to be heated inside the stove so it's a wash. The difference is with comfort factor. Consuming inside air means that cold air will have to replace it usually resulting in uncomfortable drafts or a danger of CO due to another flue reversing.

It is better for the flue to draw dry outdoor air than humid indoor air that can condense in the flue. If you don't have an OAK the more frequent air changes will increase dryness.

An OAK is not a cure for bad draft or stack effect induced negative pressure. IMHO an OAK can make a bad thing worse. If there is a pressure deficit, the OAK can push smoke into the house. The pressure of the outside air can supercharge a fire and if the stove cannot regulate it you can have a runaway situation. I had that problem but I solved it by controlling the zipper air.

Another problem I had was my flue constantly drawing heat out of the house when the stove was not in use and the cold air from the OAK turning my stove all frosty. I added a positive shutoff to the OAK to stop the air flow.

All that said, I would still install an OAK if I didn't already have one.

"Thank you LL, this kind of info is why this site exists. I appreciate it."

 

[Battenkiller]

Consuming inside air means that cold air will have to replace it usually resulting in uncomfortable drafts or a danger of CO due to another flue reversing.

But will an OAK prevent this?

The 1990 National Building Code (NBC) of Canada had mandatory requirements for outdoor air supplies for fireplaces, but, when the findings of Canada Mortgage and Housing Corporation (CMHC) research on outdoor air supplies were tabled during the revision cycle leading to the 1995 edition, the requirements were removed.


The 1990 NBC contained the following Article (clause): "9.22.1.4 Combustion Air. Fireplaces, including factory-built fireplaces, shall have a supply of combustion air. (See Appendix A)"

Appendix A-9.22.1.4. read in part: "The intent of this Article is to allow the fireplace to be operated without affecting, or being affected by, other appliances or exhaust equipment. For this to occur, the fireplace must be provided with a supply of combustion air dedicated to the fireplace only; an opening to the exterior should be provided at or near the fireplace opening."

The Article went on to require outdoor air for factory-built fireplaces in accordance with the manufacturer's instructions and gave a series of prescriptive requirements for outdoor air supplies for site-built masonry fireplaces.

In the proposed revisions sent out for public comment in August 1993, it was proposed to delete Appendix note A-9.22.1.4. with the following reason given: "Combustion air supplies as currently prescribed are generally ineffective. The requirement to provide combustion air is being deleted from CAN/CSA A-405, Design and Construction of Masonry Chimneys and Fireplaces and from the Code."

The '95 NBC contains the following: "9.22.1.4. Combustion Air. Where a supply of combustion air is provided directly to the fire chamber of a fireplace, including a factory-built fireplace, the installation shall comply with the "Outdoor Air Supply" requirements provided by CAN/CSA A-405, Design and Construction of Masonry Chimneys and Fireplaces." This is the only reference to combustion air for fireplaces.

The supply of outdoor air was made non-mandatory and this wording was included because the CMHC research that showed outdoor air supplies to be ineffective, also showed that direct-to-combustion chamber supplies could be hazardous because of the potential for wind-induced reverse flow of combustion gases through the supply duct. The A-405 requirements proposed ways to provide outdoor air safely if you choose to supply it.

Like most building codes in North America, the NBC included outdoor combustion air requirements for combustion equipment on the assumption that it was a good strategy to reduce spillage susceptibility. Unfortunately the assumption was acted upon before any research had been done to explore how outdoor air supplies actually behave.

The research reports that influenced the Standing Committee of Part 9 of the NBC are:

1) Fireplace Air Requirements, ORTECH for Canada Mortgage and Housing Corporation, 1989

2) The Effects of Glass Doors on Masonry Fireplace Spillage and Surface Temperatures, Virginia Polytechnic Institute for Canada Mortgage and Housing Corporation, 1994

Copies of these reports are available from the CMHC information centre at (613) 748-2367.

Although the two studies were conducted by two labs with different set-ups, different protocols and different appliance types (1. factory-built, 2. masonry), they arrived at the same conclusion: The susceptibility to combustion spillage due to room depressurization is not affected in a predictable way by the presence or absence of air supplied from outdoors, whether supplied to the combustion chamber or indirectly through a supply duct terminating near the fireplace.

In both studies the reference room depressurization at which spillage was induced was 10 Pa. In 'Fireplace Air Requirements', none of the five tested fireplaces spilled at 5 Pa depressurization despite the fact that all were very different in their configurations and features, although all did have glass doors. The tests at the two depressurization levels were done with and without outdoor combustion air supplies.

Once the research findings were in and analyzed, the underlying physical process became clear: That is, air flows to a zone of lower pressure through any available opening, regardless of our wishful thinking. In retrospect, this principle appears rather obvious, although for most of us it was not until revealed in the lab.

As a result of the findings of these two studies, and against the backdrop of dozens of other CMHC studies of combustion venting and building aerodynamics, it was recognized that managing the indoor pressure environment was the only viable option for preventing health- and life-threatening combustion spillage from chimney-vented atmospheric appliances. This is particularly the case with automatic oil and gas equipment of this type because they have dilution devices downstream of the combustion chamber: barometric draft controls in the case of oil appliances and draft hoods in the case of gas appliances. Dilution air cools the exhaust, weakens draft and offers a ready path for combustion spillage, roughly equal to the spillage susceptibility of open fireplaces. Automatic operation of gas and oil systems takes place independently of householder knowledge and participation and may continue for long periods undetected and that is why this type of spillage is considered potentially life-threatening.

But it was also recognized that hand-fed controlled combustion woodburning equipment does not use dilution devices and has high spillage resistance during most operational periods except for the tail out of the coalbed phase of the fire.

 

[LLigetfa]

Consuming inside air means that cold air will have to replace it usually resulting in uncomfortable drafts or a danger of CO due to another flue reversing.

But will an OAK prevent this?

If the wood burning appliance is the sole culprit causing the pressure deficit that results in another flue reversing, then the answer is YES. If you have significant air leakage from stack effect or another competing source of air loss, the answer is MAYBE. In extreme cases, the OAK could push smoke from the wood stove into the home.

If a home is fairly air tight, meaning air infiltration is kept to a minimum, and if there is not enough makeup air provided to the home, the wood burning appliance could create enough of a low pressure to cause another passively vented appliance flue to reverse.

 

[Battenkiller]

Good to know, LL.

I can't fit an OAK directly to my older stove AFAIK, but I was thinking of piping in air to a point just below the draft opening in the back of my stove. Any idea how that might improve things? I have a basement installation that has always given me fits (relative humidity wise) because that's where my musical instrument repair shop is located. Those things really don't like an RH of <6% that I sometimes go down to in the coldest weather.

 

[LLigetfa]

A near ideal situation would be a house that does not leak out warm air so that the neutral pressure plane is down at floor level. I like to use a hot air balloon as an example as it has a large hole at the bottom yet holds in the hot air. If a home is sealed well enough you can have a large opening providing makeup air and it will draw only what the home needs to service flues and exhaust fans.

If however, air leaks out through the envelope as fast as you can replace it, letting in more air will result in losing more of the warm humid air. If the makeup air vent located in close proximity to the stove supplies only as much air as the stove consumes, it should help retain humidity in the home. It would reduce the amount of cold drafts there are through the building envelope and heat the cold air where there is more than enough hot air. Modern homes often have a makeup air vent piped in to the cold air duct of the furnace and the furnace fan will suck in the cold air to heat and pressurize the home.

 

[bag of hammers]

This is the part that scares me:

"CMHC research that showed outdoor air supplies to be ineffective, also showed that direct-to-combustion chamber supplies could be hazardous because of the potential for wind-induced reverse flow of combustion gases through the supply duct."

The site woodheat.org, sometimes referenced here, does not recommend an OAK, as many of you probably know. And that site also has some great info, I believe.

Seems like many discussions I find (as a DIY'er) involve science vs practical experience (e.g. anyone ever had / seen an OAK related house fire?). I guess it depends on particular circumstances, stove placement, chimney design, house characteristics, etc. - and maybe it's an extreme or a worst case, but when I read about the potential for chimney gasses to go out the OAK, that makes me worry.

I have my hearth almost built and an opening under the pedestal for the OAK (not yet vented to outside). Thinking twice. Nothing is simple.

 

[BrotherBart]

The counterpoint.

http://www.chimneysweeponline.com/hooa3.htm

 

[Smokey Bear]

Could you possibly run a pipe of some kind connecting your attic (assuming its ventilated) to the basement, it would help with combustion air for your wood stove and any other appliances that need combustion air.

 

[North of 60]

Having an OAK has helped control my house humidity, unwanted drafts and ice build up around my doors and windows.
My 2 cents for my climate.

 

[vvvv]

Even though the OAK may not fully develop a backdraft, the variations of the windspeed will develop a pulsation in the draft's strength

 

[John_M]

VCBurner, My house is 5 years old, well insulated, and tightly wrapped. How do I know? I built it. My lungs are compromised from TB I had a child and have been very sensitive (asthma and chronic bronchitis) to contaminated air for as long as I can remember. For the last four years I would have various and sometimes frequent lung difficulties from time to time during the winter. These respiratory episodes were annoying and uncomfortable, but not life threatening.

Last fall I installed a new woodstove (see my signature) w/an OAK providing outside air to the stove from under the pedestal. This winter I have had few if any of the breathing difficulties I had suffered during the previous four years. I would speculate that either my lungs have experienced a miraculous cure (highly unlikely at 71 years of age) or the wood stove w/OAK have improved the quality of my home's inside air. The stove has been burning just about 24/7 since late September. Since then I have noticed NO drafts or other negative changes to indoor air. But, I am definitely breathing much easier this year than my previous forty. ;-) This is just MY experience. Take if for what it is worth. John_M

 

[Hogwildz]

I don't know why you need a new thread for this, just use the forum search, its been beaten to death, I don't think any of the veterans want to do this again...

But I have to comment on one thing you said:

It makes sense to use an OAK not only for the air quality inside the house

This is wrong. Indoor air quality suffers from using an OAK, the reason is that without the OAK your home's natural air exchange (ventilation) is higher. Often installers who recommend OAKS also strongly recommend installing a separate air exchanger for your home. Personally I think if you go with an OAK some kind of house air exchanger should almost be required.

Its worth noting that some jurisdictions that formerly required OAKs have since realized that the requirement didn't make sense, and they have removed these rules.

"Hey Gordo, if you don't want to comment, don't comment!! I read a lot of your posts including videos, etc... I found some of the info very helpfull. But the thread is there for all who want to read it and respond to it so if you don't care to then don't. Good night sir!"

Gordo made a good point. Don't take offense to it.
This question has been posted many times, and is always the same discussions/arguments etc.
There is no need to fill the new posts up with questions that have been posted, dealt with, argued about etc.
This takes up space for other questions & posts that may have not been answered or touched upon.
This is not an attack, just stating fact. And a search will provide all the answers your looking for.
Twas good advise, no need to take it personally.

 

[Highbeam]

It is silly to think that the stove would backdraft through the intake plumbing in any case other than a small explosion in the woodstove. Which would be temporary. You have a heat source attached to a vertical stack providing a strong draft. Your intake plumbing should be installed to provide a positive draft to the stove and in all cases will provide a lesser draft than the actual chimney. Click on my signature link for an OAK system that is completely unaffected by outdoor wind.

Are you sitting on some mountain top where the wind creates extreme conditions?

The woodheat site has gotten this one wrong. My state actually requires the outdoor air connection. Of course it doesn't burn houses down.

 

[Troutchaser]

I don't know why you need a new thread for this, just use the forum search, its been beaten to death, I don't think any of the veterans want to do this again...

But I have to comment on one thing you said:

It makes sense to use an OAK not only for the air quality inside the house

This is wrong. Indoor air quality suffers from using an OAK, the reason is that without the OAK your home's natural air exchange (ventilation) is higher. Often installers who recommend OAKS also strongly recommend installing a separate air exchanger for your home. Personally I think if you go with an OAK some kind of house air exchanger should almost be required.

Its worth noting that some jurisdictions that formerly required OAKs have since realized that the requirement didn't make sense, and they have removed these rules.

"Hey Gordo, if you don't want to comment, don't comment!! I read a lot of your posts including videos, etc... I found some of the info very helpfull. But the thread is there for all who want to read it and respond to it so if you don't care to then don't. Good night sir!"

Gordo made a good point. Don't take offense to it.
This question has been posted many times, and is always the same discussions/arguments etc.
There is no need to fill the new posts up with questions that have been posted, dealt with, argued about etc.
This takes up space for other questions & posts that may have not been answered or touched upon.
This is not an attack, just stating fact. And a search will provide all the answers your looking for.
Twas good advise, no need to take it personally.

I don't want to step in it here, but realize that different folks are on this site now that may have new information to contribute to any posted subject. Following this "old topic" logic, there would be very few legitimate posts.

 

[Lumber-Jack]

I don't know why you need a new thread for this, just use the forum search, its been beaten to death, I don't think any of the veterans want to do this again...

But I have to comment on one thing you said:

It makes sense to use an OAK not only for the air quality inside the house

This is wrong. Indoor air quality suffers from using an OAK, the reason is that without the OAK your home's natural air exchange (ventilation) is higher. Often installers who recommend OAKS also strongly recommend installing a separate air exchanger for your home. Personally I think if you go with an OAK some kind of house air exchanger should almost be required.

Its worth noting that some jurisdictions that formerly required OAKs have since realized that the requirement didn't make sense, and they have removed these rules.

"Hey Gordo, if you don't want to comment, don't comment!! I read a lot of your posts including videos, etc... I found some of the info very helpfull. But the thread is there for all who want to read it and respond to it so if you don't care to then don't. Good night sir!"

Gordo made a good point. Don't take offense to it.
This question has been posted many times, and is always the same discussions/arguments etc.
There is no need to fill the new posts up with questions that have been posted, dealt with, argued about etc.
This takes up space for other questions & posts that may have not been answered or touched upon.
This is not an attack, just stating fact. And a search will provide all the answers your looking for.
Twas good advise, no need to take it personally.

Don't know much about OAKs, don't have one, don't see that I need one, but I think it's much more refreshing to have one's question answered with up to date responses, that's what forums like this are all about. Obviously there is still something to be said about it because the veterans and moderators are still responding.
As for "saving space" and using the search option, the search button is a nice feature to have, but that's not what forums like this are all about, and I don't think Craig is in any danger of running out of cyber space any time soon.
Reponses questioning the justification of the original poster's need to start a new thread are unnecessary and off-topic (and just waste space ;-) ), however I think VCBurner handled the response well, I didn't detect he took it too personally at all.

 

[VCBurner]

author="Hogwildz" date="1268170155
Gordo made a good point. Don't take offense to it.
This question has been posted many times, and is always the same discussions/arguments etc.
There is no need to fill the new posts up with questions that have been posted, dealt with, argued about etc.
This takes up space for other questions & posts that may have not been answered or touched upon.
This is not an attack, just stating fact. And a search will provide all the answers your looking for.
Twas good advise, no need to take it personally.

Thank you for posting on this Hogwildz. I am not offended! ;-) I posted this thread back in January, shortly after I found this site. I as a new stove owner, I found this site very helpful and entertaining. A wealth of knowledge can be found in it, so I have learned. I have learned how to use the site a little better. I agree, that multiple posts on the same subject could be annoying to some. However, I though this was an open forum and any question could be asked as long as it is stove related. The readers can choose to skip by that thread if it is repetitive. I guess there could be a positive side repeat posting on certain subjects. New ideas and emerging technologies could be shared about old questions. I have disconnected the stove on the original post. But the subject has aparently stayed alive, even though I no longer need the answer. I hope it will help another member who may have the same question.

 

[VCBurner]

VCBurner, My house is 5 years old, well insulated, and tightly wrapped. How do I know? I built it. My lungs are compromised from TB I had a child and have been very sensitive (asthma and chronic bronchitis) to contaminated air for as long as I can remember. For the last four years I would have various and sometimes frequent lung difficulties from time to time during the winter. These respiratory episodes were annoying and uncomfortable, but not life threatening.

Last fall I installed a new woodstove (see my signature) w/an OAK providing outside air to the stove from under the pedestal. This winter I have had few if any of the breathing difficulties I had suffered during the previous four years. I would speculate that either my lungs have experienced a miraculous cure (highly unlikely at 71 years of age) or the wood stove w/OAK have improved the quality of my home's inside air. The stove has been burning just about 24/7 since late September. Since then I have noticed NO drafts or other negative changes to indoor air. But, I am definitely breathing much easier this year than my previous forty. ;-) This is just MY experience. Take if for what it is worth. John_M

Thank you John,
Your experience has enlightened me and I hope will help others also!

 

[semipro]

I've burned 5 different stoves in 3 different houses all with and without OAK installations. I experimented a lot. In every case the OAK installation provided a perceived and sometimes measurable improvement in the warmth in the house as drafts around windows and doors were decreased. I use a data logger with 4 channels of temperature recording to compare operation with and without outside air. (I'm now using the same data logger to gauge the effects of mods to my geothermal heating system).

In a perfect world my house would be airtight, my stoves would have OAKs and I'd use a heat recovery ventilator to provide filtered fresh air while recovering heat from the exhausted air. I'm not there yet.

 

[VCBurner]

Thanks Semipro,
Sounds very intersting. I'm not familiar with data loggers or the idea of a heat recovery ventilator. But, I understand numbers and charts well enough to log data by hand and draw conclusions from it. I'd love to understand more about your operation. I also run a heat reclaimer(not connected at the moment), which uses heat from flue gasses in the pipe connectors to blow hot air. The magic heat puts out up to 30,000 btu's. The idea of sucking in air from outside to run through such a device sounds excellent Great reply, thanks again.

 

[Highbeam]

The heat recovery ventilator that semipro is talking about has no similarity to a magic heat device.

 

[VCBurner]

The heat recovery ventilator that semipro is talking about has no similarity to a magic heat device.

Could you explain the heat recovery ventilator?