fresh air kit

[cyclone]

I have installed in my finished basement a TL 300 Harman wood stove. I am a new wood burner and trying to do everything correct. If it was not for this forum and everybody's help I would be lost. Being a first year burner I am always doing some research and probably will never stop.

My question? Why a fresh air kit? What does it do? How can you tell if you need one?

My stove is capable of having one and was suggested. Looking for thers opinions..

 

[mike1234]

The fire is going to use up oxygen from the house. If your house it tight, it will use it up, and then die, or just smolder, or start sucking it down the chimney (smoke in the house). So fresh air is needed for the fire to burn correctly, thus the fresh air supply kit.
I installed mine with PVC. I cut a hole in the overhang, put a vent cover over it, and ran PVC through the attic down to the stove. I only used 2" PVC, I think that was a mistake, need 4" or maybe even 6". I'll need to change that soon. Put a valve in it if you want to stop AC air flow out during the summer.

 

[TreeCo]

Fresh air is not needed. It is a myth!


The only way a wood stove can use up the oxygen in a house is if it has caught the interior of the house on fire!

 

[Firestone]

Greetings: In our sitation, the fresh air supply was mandatory by city building code. When I learn how, I will post photos of mine, it turned out very nice and looks good. I found info on the Canada Housing and Mortage Website, and discovered that originally fresh air was required for mobile homes/trailers and is in fact not necessary for stick built houses unless they are super airtight. The inspector would not even allow an open window to be used, I have a large window 2 feet from the stove. Unfortunatly once a rule is put into place by a city, it is impossible to have it rescinded, and of course your insurance company will use their "weasle clauses" if you bypass local codes and a mishap occurs.

 

[begreen]

There are lots of opinions, pro and con, about outside air kits (OAKs). In some states they are required for new installations and for mobile home installations. They are of greatest benefit when there may be negative interior pressure present. Often this is in houses that are very well sealed and in basement installations. Do a search here for OAK or outside air kit and you'll find some lively discussions on the topic. And here are a couple articles from Tom Oyen's library on the subject.

(broken link removed to http://www.chimneysweeponline.com/hooa.htm)
(broken link removed to http://www.chimneysweeponline.com/hooa3.htm)

 

[Todd]

Fresh air is not needed. It is a myth!


The only way a wood stove can use up the oxygen in a house is if it has caught the interior of the house on fire!

Outside combustion air is not a myth. Where would you rather have your stoves make up air drawn from? Cold air from cracks and leaky windows that create cold drafts and negative pressures or a direct vent right to your wood stove? Whether your house is tight or not, outside air will increase your stoves efficiency.

 

[North of 60]

Fresh air is not needed. It is a myth!


The only way a wood stove can use up the oxygen in a house is if it has caught the interior of the house on fire!

I could not operate my stove properly to maintain a comfortable house without an OAK. Humidity also plays a big factor in my climate. I suggest you do a search on this subject. Its certainly not a myth. Argumentative yes, but not a myth. Depending on your climate.

 

[cyclone]

Any users with the TL 300 wood stove with the outside air kit..

 

[North of 60]

Any users with the TL 300 wood stove with the outside air kit..

Murry, I had a look at that stove. WOW nice unit. Cookin the steaks had my mouth watering. Any how, its not relative if others have or use the kit. Its about your setup your home and your climate. The only thing to me that would rule out an OAK in my home is if I had an HRV/Heat Recovery Ventilation system in my home that always supplied fresh air which then would not matter about the huge difference's in saving money to humidify. It then would be a given I would need more humidification no matter what, but at least I would know where my fresh air is coming into the house. CHEERS
N of 60

 

[cyclone]

As mentioned I live in a ranch home. The stove is located in the finished basement. As for climate Pennsylvania varies this time of year but is relatively cold.

 

[North of 60]

As mentioned I live in a ranch home. The stove is located in the finished basement. As for climate Pennsylvania varies this time of year but is relatively cold.

Well if you dont have an HRV and you have a Cold dry climate in the winter as this is when you would be using your stove then I would say an OAK is a win win situation.
EDIT; The stove manufacture boasts the OAK ready for a reason.

 

[MadTripper]

As mentioned I live in a ranch home. The stove is located in the finished basement. As for climate Pennsylvania varies this time of year but is relatively cold.

Where abouts in PA? I've considered putting an outside air attachment on my stove but it is in the basement (which is mostly above ground) and I don't have it sealed up. The living area is sealed fairly well, new stick built home, and I use a blower to push the hot air upstairs through some duct work.

Tripper

 

[Ivy Frank]

Outside air is the only way to go, IMO.

1. You don't burn heated house air. If you don't use outside air, go take a look at your vent stack when you first add wood and it's smoking a bit. See the volume of air coming out of the chimney? That's the volume of warm house air that is being sucked out of your house. It's just stupid to burn air you already heated.

2. You don't suck dry winter air into your house. That same volume of warm, moist air is replaced with dry, outside air.

3. Outside air has more oxygen per volume.

No you don't "need" outside air. You don't need to floss everyday either - but it's the superior method.

 

[Highbeam]

Frank's right, and as others have said it is a superior setup to have OAK. Also, it can't hurt a bloody thing. There's no negatives and lots of positives. I installed mine and took some photos for a thread. See the link in my sig.

 

[Nic36]

Frank's right, and as others have said it is a superior setup to have OAK. Also, it can't hurt a bloody thing. There's no negatives and lots of positives. I installed mine and took some photos for a thread. See the link in my sig.

The one possible negative I can think of:

(I installed an OAK at the same time I installed my stove. I think it works just fine and does what everyone claims.)

But, the only thing I am concerned about is to the amount of moist air it draws in from the outside, especially when the stove is not in use. I wonder if anyone has had a problem with OAKs rusting out their stoves? I think after burning season, I will close mine off just to be on the safe side.

 

[TreeCo]

Outside air is the only way to go, IMO.

1. You don't burn heated house air. If you don't use outside air, go take a look at your vent stack when you first add wood and it's smoking a bit. See the volume of air coming out of the chimney? That's the volume of warm house air that is being sucked out of your house. It's just stupid to burn air you already heated.

2. You don't suck dry winter air into your house. That same volume of warm, moist air is replaced with dry, outside air.

3. Outside air has more oxygen per volume.

No you don't "need" outside air. You don't need to floss everyday either - but it's the superior method.

1) The net energy loss is the same either way! Cool outside air cools down the wood stove and gets heated anyway so there is no net difference in heating efficiency! The cool outside air may even decrease combustion efficiency by cooling the firebox below efficient combustion temps.

2) If wintertime indoor humity is too low then most likely your house is too leaky to begin with!

3) If there is any significant difference between oxygen levels inside Vs. outside your house......then you don't have enough air exchange to begin with! An outdoor air supply would make the condition even worse by reducing air exchange rates evern further, and indoor air use would increase oxygen levels.


Of course oyxgen defeciency just may explain the lemming like desire for outside air supplies. (just joking, of course)

Be leary of advice given by people who stand to profit by selling a product.

 

[Ivy Frank]

Frank's right, and as others have said it is a superior setup to have OAK. Also, it can't hurt a bloody thing. There's no negatives and lots of positives. I installed mine and took some photos for a thread. See the link in my sig.

The one possible negative I can think of:

(I installed an OAK at the same time I installed my stove. I think it works just fine and does what everyone claims.)

But, the only thing I am concerned about is to the amount of moist air it draws in from the outside, especially when the stove is not in use. I wonder if anyone has had a problem with OAKs rusting out their stoves? I think after burning season, I will close mine off just to be on the safe side.

Um, if you're worried about air in the pipe during the off season, just slap a cover on the draw end of the feed. Even a plastic bag.

But it is true that a good chimney will always be drafting air, even if the stove is off.

 

[Ivy Frank]

Outside air is the only way to go, IMO.

1. You don't burn heated house air. If you don't use outside air, go take a look at your vent stack when you first add wood and it's smoking a bit. See the volume of air coming out of the chimney? That's the volume of warm house air that is being sucked out of your house. It's just stupid to burn air you already heated.

2. You don't suck dry winter air into your house. That same volume of warm, moist air is replaced with dry, outside air.

3. Outside air has more oxygen per volume.

No you don't "need" outside air. You don't need to floss everyday either - but it's the superior method.

1) The net energy loss is the same either way! Cool outside air cools down the wood stove and gets heated anyway so there is no net difference in heating efficiency! The cool outside air may even decrease combustion efficiency by cooling the firebox below efficient combustion temps.

Interesting point, but not, I think, compelling. As a preliminary matter, the comparison is not apples to apples.

Calculation A - When you burn inside air, your net heat loss is definitely the amount of heat energy it takes to raise the volume of air you're sucking into your house from the outside the difference in temp between outside and inside.

When you're burning outside air, on the other hand, your argument that you suffer a loss of heat output on your stove equivalent to calculation A is generally incorrect. For example, my outside air run traverses about 40 feet of unheated basement, which means, minimally, that I have mother earth warming up the incoming air before it reaches the stove.

I'll have to think about this more - it is an interesting point.

2) If wintertime indoor humity is too low then most likely your house is too leaky to begin with!

Huh? The reason we're even talking about humidity is because a stove that consumes house air draws in outside air, which makes it dryer inside.

3) If there is any significant difference between oxygen levels inside Vs. outside your house......then you don't have enough air exchange to begin with! An outdoor air supply would make the condition even worse by reducing air exchange rates evern further, and indoor air use would increase oxygen levels.

I agree with this. You certainly get more fresh air when you burn a stove using inside air. Cold, dry, fresh air, but fresh air nonetheless.

Be leary of advice given by people who stand to profit by selling a product.

We agree on this as well.

In any event, there's no doubt about this . . .

Using inside air does one of two things . . .

1. If your house is tight, you'll have poor draft.
2. If your house is not tight, you'll have cold air being sucked in through windows and doors to your stove, which is much less comfortable than still air.

If you don't use an outside air feed, you will have to heat your house up to a warmer temperature to feel the same level of comfort.

 

[TreeCo]

Frank,

How may cubic feet of air per hour does a wood stove draw? (Pick a size stove)


What is the suggested air exchange rate for a house?


I don't know these figures, that's why I'm asking. It is my understanding that a wood stove draws far less air than a 'healthy' air exchange rate in a house should be able to supply.


I used a Jotul 3cb for 7 years in a very tight house insulated to electric heating standards and had adaquate draft.

I'm now using a Jotul F600cb without outside air and am making out fine.

My bet is most houses have more then enough air exchange and running outside air really makes little difference in heating ability and comfort. This has been my experience in just over 30 years of heating with wood. I have experimented with outside air supplies, I just don't think they are as necessary in most cases as many are saying.

 

[Slow1]

Outside air is the only way to go, IMO.

2) If wintertime indoor humity is too low then most likely your house is too leaky to begin with!

Huh? The reason we're even talking about humidity is because a stove that consumes house air draws in outside air, which makes it dryer inside.

(Sorry for nested quotes, I don't dare try to untangle more for fear of misquoting folks!).

Anyway - I want to jump in here with another thought on the question of OAK burning efficiency. Note that my only financial interest in these is that I'm debating if it may be worth one on my stove.

So my thought is this - Given that many of us do indeed put forth effort to add humidity to our inside living air and the air outside is much drier, there is more water in the inside air than outside. Thus does it make sense that if one is burning the much drier air outside it would take less energy to get it up to burning temps? I don't know exactly how many cuft of air goes through a stove nor do I know how many grams of water are in each cuft, but if one were to do the calculation we could actually figure out how many calories are lost just heating the water in the air to toss it up the chimney eh? 1 cal/g/degreeC - with a 500degreeC difference between air and fire temp at peak combustion temp it would seem to me that the water in the air would make a far greater difference in the firebox heating rate than the original starting temperature of the air. It simply takes more energy to heat wet air than dry eh? Perhaps this makes for an interesting argument for OAKs, don't know if once the calculation is completed if it really would be a material argument or not though.

 

[Todd]

I think someone said a while back that a wood stove can draw 50-100 cfm, so think of it like a 4" hole in your wall with one of those small doorway fans installed into it. That's alot of cold air being drawn into house!

I was a skeptic too, but went ahead and installed it in my two wood burners and found it does make a big difference, especially for my fireplace.

 

[Ivy Frank]

I think someone said a while back that a wood stove can draw 50-100 cfm, so think of it like a 4" hole in your wall with one of those small doorway fans installed into it. That's alot of cold air being drawn into house!

I was a skeptic too, but went ahead and installed it in my two wood burners and found it does make a big difference, especially for my fireplace.

I've done this math before. Let's say it's 50 cubic feet per minute, which sounds about right for a small stove - just under a cubic foot a second.

That's 50x60 cfh, or 3,000 cubic feet per hour, or 72,000 cubic feet of air per day.

Now figure the average 2000 square foot house has 8 foot walls, and you get 16,000 cubic feet in a house. That means that you're exchanging all of the air in your house about 4 times per day.

 

[cyclone]

With everything mentioned I may have solved some of my problems. My stove may actually be to big for my home. A fresh air kit just might do the trick.

 

[TreeCo]

I think someone said a while back that a wood stove can draw 50-100 cfm, so think of it like a 4" hole in your wall with one of those small doorway fans installed into it. That's alot of cold air being drawn into house!

I was a skeptic too, but went ahead and installed it in my two wood burners and found it does make a big difference, especially for my fireplace.

I've done this math before. Let's say it's 50 cubic feet per minute, which sounds about right for a small stove - just under a cubic foot a second.

That's 50x60 cfh, or 3,000 cubic feet per hour, or 72,000 cubic feet of air per day.

Now figure the average 2000 square foot house has 8 foot walls, and you get 16,000 cubic feet in a house. That means that you're exchanging all of the air in your house about 4 times per day.

Quote from an EPA site of household air exchangee:

"How much ventilation do I need?
The American Society of Heating, Refrigeration and Air-Conditioning Engineering (ASHRAE recommends (in its Standard 62-1999, "Ventilation for Acceptable Indoor Air Quality") that homes receive .35 air changes per hour, but not less than 15 cubic feet per minute (cfm) per person. "

(broken link removed to http://www.epa.gov/iaq/homes/hip-ventilation.html)


Frank,
Your math is showing a wood stove that creates 4 air exchanges per day. Here is information from the EPA that is saying a house should have .35 air exchangeses per hour......or a total of 8.4 air exchanges per day!

The figures look to be saying that a house designed with healthy indoor air quality in mind would already have double the air exchange rate required to run a wood stove.

If a house does not have the EPA suggested air exchange ratio........an outdoor air supply is not the answer! It actuality leads to fewer air exchanges per day....and results in higher indoor air pollution levels! Combined with a small amount of wood smoke spillage that even an expert user experiences from loading, etc., it makes OAS's look even worse.

Frank can you point us to some research that backs up your opinion?

 

[PeteD]

Outside air is the only way to go, IMO.

1. You don't burn heated house air. If you don't use outside air, go take a look at your vent stack when you first add wood and it's smoking a bit. See the volume of air coming out of the chimney? That's the volume of warm house air that is being sucked out of your house. It's just stupid to burn air you already heated.

2. You don't suck dry winter air into your house. That same volume of warm, moist air is replaced with dry, outside air.

3. Outside air has more oxygen per volume.

No you don't "need" outside air. You don't need to floss everyday either - but it's the superior method.

1) The net energy loss is the same either way! Cool outside air cools down the wood stove and gets heated anyway so there is no net difference in heating efficiency! The cool outside air may even decrease combustion efficiency by cooling the firebox below efficient combustion temps.

2) If wintertime indoor humity is too low then most likely your house is too leaky to begin with!

3) If there is any significant difference between oxygen levels inside Vs. outside your house......then you don't have enough air exchange to begin with! An outdoor air supply would make the condition even worse by reducing air exchange rates even further, and indoor air use would increase oxygen levels.


Of course oyxgen defeciency just may explain the lemming like desire for outside air supplies. (just joking, of course)

Be leary of advice given by people who stand to profit by selling a product.

1) Ever hear of a supercooler to increase horsepower? Counter-intuitive maybe, but you will get better combustion with cooler (denser) more oxygen (more efficient burn). You won't hear about someone slapping a "superheater" on their hot rod. Incidentally, one part of what nitrous oxide does to increase horsepower is lower the temp of the intake air.

2) If your house is too leaky (and dry), then why not use an OAK to make it less leaky by reducing the pressure gradient from outside to inside?

3) Not true. The varying oxygen level is based on temperature. To get the same oxygen level inside the house per volume, you would have to lower the temperature inside to the outside temperature. Also, if a house is too tight, it create draft problems with the fireplace or maybe other appliances - better to have an OAK.

In my opinion, there all about positives and no negatives to having an OAK - except for having another vent to install/maintain/prevent leaks around (as needed).

Edit:
BTW, humid air is also less dense than dry air. Someone can correct me if I am wrong, but neglecting pressure differences, I calculate that 10 F air has 15% more oxygen per volume than 80 F air. Nothing to sneeze at when you factor in how dry that outdoor air will be also. Water vapor is certainly not your friend for combustion.

Pete