Is this flow reversal? Is there any way to stop it?

[EatenByLimestone]

I know I have some flow reversal, when I was installing the thimble, I could feel the air coming down the chimney. I'm not sure if this is my problem though.

When my stove is off, and the chimney is cold, I get a campfire smell in the room. When the stove is on, and the flue is warm, the smell disappears.

I only burn the stove at night. Partially because our days are still warm, a bit of convenience, but mostly piece of mind. I'm still not comfortable leaving the stove lit when nobody is at home.

A few nights ago we had a wind advisory and I noticed a few downdrafts where smoke would puff out the seams in the (2) 45s in the pipe. Sometimes on a strong one I'd catch it coming out the intake damper. This has only happened that night, so it's probably wind related and not a reoccuring problem.

When the stove is off, I've started closing the intake damper so the smell will not enter the room. While this may have helped, it didn't stop all of it. Is flow reversal pushing this smell out of the joints in my pipe elbows? Should I seal them with gasket cement? I had been trying to avoid this incase I wanted to change the routing of my pipe off the stove. After the newspaper trick, I seem to have a pretty good starting draft so I may keep the pipe as it currently is.

Is there any way to stop this smell from entering the room? What about during the non heating season?


Thank you,

Matt

 

[elkimmeg]

Mat some have claimed sucess by cleaning the chimney after the season and sprinkling baking soda down the chimney others have place a box of baking soda in the fire box as well'

Yes adjustiable elbows are not air tight they can leak For single wall pipe there is a choice standard 24 gage using flexible elbows
22 gage welded seams fixed elbows It cost more it last longer but could s prevent some of the leakage you are experincing

Again yes ypu could seal the joints best done by placing a bead of cement on the connection area before you insert the pieces Sealing the joints afterwards the thin gasket cement woll dry out and flake off for some this has worked. Next time I replace my connector pipes, it will be 22 gage

here is an example of cost

Heat Fab 22, gage welded seam stove pipe 2" lengthe $12.60 fixed 90 degree elbow $15.42 45 fixed elbow $13.22 Im quoting 6" pipe from copperfielsd

Dura Vent 24 gage welkded seam black stove pipe 2" length $10.55 90 elbow $ 11.93 45 elbow $9.50

as a comparison 24 gage snap lock adjustiable elbows 2" length $6.28 90 adjust elbow $6.28 45 no need to price 45 the 90 adjust to that angle

22 gage welded cost twice as much but it last longer

 

[webbie]

You do have flow reversal and I know of no sure way to stop it. Certainly you can slow it down, as Elk mentions, but whether that really does any good is questionable. It only takes the tiniest amount of "chimney smell" to stink up the room.

The only surefire solution is a chimney fan - very expensive also.

Th $10 solution is a bottle of Fireplace and Stove deodorant. It really works!

 

[senorFrog]

Not for flow reversal, but for the wind related down draft, check this out...

http://www.chimneycaps.com/

They have some PDF files there with good explanations.

 

[jabush]

I get some downdraft action myself when the stove is not burning. I could smell it prior to sweeping the chimney and getting all that black, wet, nasty, "cold patch looking" creosote out of my chimney trap. Once the trap was clean, I sealed my cleanout door tightly and haven't smelled the stove since.
I don't know what setup you have for a chimney, but if it's exterior with a cleanout door and trap, clean that puppy out. It's a nasty job but it makes a big difference (smell wise).

 

[Roospike]

I had a friend that had that issue in his wood stove and he only burned wood at night and on the weekends , He burned big fat cheap candles in his stove to keep the draft going up when he was not burning wood.
Take the idea for whats its worth , it worked but you had to buy a new candle 1 a week or 1 every 2 weeks.

 

[fastrac]

Well you guys ready for this?

I think I can have most homeowner correct most of there flow reversal problems simply.

Give me a description of your home, inclusing what type of heat you have and where its located.

Let me know whats on the top floor of the house

including any type of opening into your attic

High hats

whole house fans

bathroom fans

unsealed attic scuttle


what is the highest part of your house

any large fans in the home

where is the dryer and what type of fuel does it use

 

[webbie]

The candles might not be enough heat for a lot of these...and then the next thing you know, the house has black soot on the walls because of the candles burning.

I want to see how FT corrects these simply and cheaply. ....he didn't say cheaply..........but I assume that is part of the deal.

Sure, there are a lot of causes of negative pressure, but I have found it in many houses where there was no good reason other than the cold exterior chimney and the "stack effect" of the home itself.

We're listening....

 

[fastrac]

Come on

give me the goods,

 

[fastrac]

The candles might not be enough heat for a lot of these...and then the next thing you know, the house has black soot on the walls because of the candles burning.

I want to see how FT corrects these simply and cheaply. ....he didn't say cheaply..........but I assume that is part of the deal.

Sure, there are a lot of causes of negative pressure, but I have found it in many houses where there was no good reason other than the cold exterior chimney and the "stack effect" of the home itself.
We're listening....

You just answered the question,

We are part of the BPI

building performance institute.

I can complete a blower door test in no time at all.

Just about every 2 story home I have tested is in a negative pressure because of stack effect and guess where it gets it air , from one of the biggest air shoots available ,the cold exterior chimney

 

[EatenByLimestone]

Getting the goods! Just a sec.

Matt

 

[Roospike]

The Evil Outside Chimney
(broken link removed to http://www.woodheat.org/chimneys/evilchim.htm)

Selecting and Locating a Chimney
(broken link removed to http://www.woodheat.org/chimneys/trichim.htm)

All about chimneys
(broken link removed to http://www.woodheat.org/chimneys/chimneys.htm)

 

[EatenByLimestone]

Well you guys ready for this?

I think I can have most homeowner correct most of there flow reversal problems simply.

Give me a description of your home, inclusing what type of heat you have and where its located.


Let me know whats on the top floor of the house

including any type of opening into your attic


Here is a pic from Spring of the home. I didn't have the chimney up yet, but this is the best photo showing the back of the house I have. My chimney up pics were all taken at night and grainy. It's located in Schenectady, NY... About where the Mohawk and Hudson Rivers come together. The chimney is masonry and comes up just to the right of the right hand window on the bottom floor. It rises to about a foot above the window on the second floor. Then there is a stainless cap to keep rain and tree rats out. The trees have been trimmed way back. They are a good 10-15 feet back from the house now.

(broken link removed)

Bottom floor figure one big room with a bearing wall right down the middle open at both ends. Added to the back of the house is a 10X20 room, where the wood stove is.

Top floor has a hallway running from left to right and a bath with 3 bedrooms. In the hallway there is a long, older style hatch.
Here is a pic: I need to get the final coat of ceiling paint on... I still have blue "pinstriping".

(broken link removed)

The hatch is insulated to R-18, but there are small leaks around it. I couldn't get the foam to fit tight on one side. The rest of the attick has been insulated to at least R19 from the previous owner. Last year I added R-38? I know it was 9.5" thick... over the back half of the house. I'll get the front half this year.

Heating is a 100K forced hot air unit that is 2 years old. It runs mostly in 80yo ductwork from what I imagine was a gravity fed system. All of the duct work is going up inside walls.





High hats

Not sure what this is, so probably not.

whole house fans

none. I just installed a small duct fan that pulls air from the back room where the woodstove is to the upstairs bedroom above it. I have it hooked up manually for now... I plug it in when I want it on. It gets turned off when the stove starts cooling down at night.

bathroom fans


The upstairs bathroom has a fan, but it is rarely used. It is vented outside. Last winter, the first winter in the house, I used the shower to keep some moisture upstairs. I didn't pick up a humidifier for up there until late in the winter.


unsealed attic scuttle


Not sure what this is. Please see the hatch photo from above.


what is the highest part of your house


attick? The ceiling of the 2nd floor would be the highest insulated part.


any large fans in the home

The furnace has one, but it's rarely on. Only in the mornings... I suppose this could cause the negative pressure to pull air down the chimney, but it certainly would have more than enough air where it didn't need to. It's an 80 year old house and far from tight.

where is the dryer and what type of fuel does it use

It's an electric dryer that is vented out the foundation, below where the vinyl siding starts. We do all our washing on the weekend.

Thank you,
Matt

 

[fastrac]

The Evil Outside Chimney
(broken link removed to http://www.woodheat.org/chimneys/evilchim.htm)

Selecting and Locating a Chimney
(broken link removed to http://www.woodheat.org/chimneys/trichim.htm)

All about chimneys
(broken link removed to http://www.woodheat.org/chimneys/chimneys.htm)

Thanks for the information, All of this should be mandatory reading for anybody selling and installing wood burning products, No one note of this is in any installation manuals I have ever read

 

[fastrac]

I hope every reads thru the links roospike gave us a link to, The first one describes it best

After reading the information roospike gave a us a link to we better understand what a bad design an out side chimney is.

But we can go further

A high hat is a recessed light. You see them all over the place. they are not very efficient because the less expensive ones when you install them you have to keep the insulation away from them, and they are not sealed up so basically you are leaving a giant hole in your ceiling to allow the heat to go up into your attic

I dont know how deep I should go with this but its real exciting stuff, (at least to me)

We have to look at the entire "house as a system" h.a.s.s. and understand its pressures and where the pressures actually change

we want to understand where the N,P,P is Neutral Pressure Plane is anything above it positive pressure and anything below it is negative pressure.

Now these pressure may not be something you notice but they are in every house.

My home is actually a positively pressurized home (everybody should be) I am controlling the amount of air I bring in and I am using an air to air heat exchanger to control it http://davelennox.com/products/overview.asp?model=HRV1

Mine is set to bring in more air then it exhaust

Anyways before I bore you all

The quick answer is most likely your home is stacking, meaning that some where on the upper level (highest part of your home) you have a leak, Yup a leak that's letting your hot air out of the home, Once it get up into the attic its no longer part of the home envelope and now the bottom of your home is starving for air and the infiltration in the basement is not enough, Even worse is we have all been told to seal up and weatherstrip every thing we can so now that its sealed you could actually be using the flue system from your gas appliance as make up air in an off cycle.

So you may say "well I will just raise my fireplace chimney till its the highest part of the home" Nope the answer is much simpler.

Find the leak in the upper level and seal them up. if the hot air stacks up to the second floor and doesn't leave the envelope then we dont need to bring in any more air (now your FP chimney is actually neutral or negative instead of positive) we all know its better to have a negative chimney then a positive one right

Seal up the top floor it fixes 80% of the problems the other 20% need a guy like me to come in and look for other leaks not so obvious. Like the old duct work in the walls going up and allowing the basement to freely communicate with the attic.

Normally the basement is part of the envelope but the attic is not so if the attic communicate to the basement there is another major leak that would cause your chimney to down draft.

Now most folks say I have no leaks upstairs. I send them into the attic then close the scuttle hole and ask them what they see

Normally its the light from the hall way So its leaking

Another bad leak is caused by us.

some one thinks its a good idea to open an upper level window to exhaust a bathroom. spend a little time looking around the top of your home for leaks no matter how minor you think they are seal them.

you start to see a night and day difference,

Don't believe me do a little test set a candle by the fireplace hearth with the fireplace off and watch the candle and how the flame acts

open the attic scuttle and watch the candle move as the air currents start to flow down your chimney then up stairs to the attic

the greater the temperature difference between the inside and the outside the more air you ll see move.

Best of luck and look around upstairs I am sure your problem is there

Remember to look at your "house as a system"

Find your easy leaks ,if you still have a problem we can take it to the next level of diagnostics

 

[Roospike]

Very good post fastrac . Lots of good information .

 

[EatenByLimestone]

Thank you for the info. I'll certainly try to find some leaks. I know it won't be hard either.

Matt

 

[Gunner]

Wow fastrac, had to read that a few times to take it all in. The HRV that you have in your house, is that similar to a "fresh air kit" or are they ever called that. Reason I ask is just bough a new house and it has what I was told was a fresh air kit. Could you explain alittle bit about what these units do and how they work?

I have also seen a hearth related site that recommend (broken link removed to http://pureairplus.com/nap.htm) specificly for woodburners to relieve such problems as mentioned in this post.

For someone with forced hot air,I take it they only work when the furnace fan is running. This may be an issue since most burners have found running the fan 24/7 is useless.


Thanks

 

[elkimmeg]

Might I expand fastrac's nuetral pressure plane and I'm sure he will concure. as I said in a past post
https://www.hearth.com/talk/threads/3855/


Your HVAC system is probably the cause of poor drafting, especially top floor ceiling feeds and returns plain and simple the common duct system leaks.
so much so that up to 35% of heat is lost in transmission. there is no substitute for the shortest possible runs and no substitute for proper duct sealing and insullation
every outlet contributes to lost pressure. Energy star homes address this issue they advocate routing ducts within the insulation envelope including locating the burner/ exchanger within the envelope. For some reason recessed lights are installed everywhere. They all leak.

Taking his explanations and applying them to insert installations, here is another good reason to have a tightly sealed damper block off plate.

To add to the debate about cutting holes in the floor or ceilings to distrobute heat, has one factored in what that does to pressurization?

Sealed duct work should leak no more than 6 cfm per 100 sq ft living space. Reality is, common duct work leaks more than 30 cfms per 100sq ft of living space
I have done final inspections in the dead of winter and enter the attic and it is confortable there. so much heat was being lost. And its not just the duct work. those builder specials furnaces /exchanger gaskets leak so badly one can feel the air flow 10' away. I have failed so many, the HVAC contractors stopped using some brands or the rtv caulk everything. I fail non sealed duct work I can fail poor routing. Iam limited as to what I can do code wise. I canot fail systems due to ceiling returns. I have to stay within the perameters of written code.

And yes exterior wall chimneys and fireplace locations are the worst possible placement. ITs done for convience so as not to cut into living space. they suck the heat out of you home threw the bricks
I'm glad an expert has taken his time to explain pressurization and prevention, but don't stop there there is more work and education needed to be done

 

[fastrac]

Wow fastrac, had to read that a few times to take it all in. The HRV that you have in your house, is that similar to a "fresh air kit" or are they ever called that. Reason I ask is just bough a new house and it has what I was told was a fresh air kit. Could you explain alittle bit about what these units do and how they work?

I have also seen a hearth related site that recommend (broken link removed to http://pureairplus.com/nap.htm) specificly for woodburners to relieve such problems as mentioned in this post.

For someone with forced hot air,I take it they only work when the furnace fan is running. This may be an issue since most burners have found running the fan 24/7 is useless.


Thanks

Well more great reading , thanks for the link to that peice of equiptment

I personally am not a fan of uv lighting. I am also not a fan of adding ozone to a home enviroment. The link I gave for the air to air heat exchanger is a lennox model. I only chose to give that link because I thought the information lennox gives kinda explains the reason we need to add air/pressure to a home

Again no home should be with out one, Solves allot of problems

There are ones that run indepently of a heating system and those are a good choice,

I dont want to get into throwing stones but most warm air systems are improperly installed. So adding a unit to bring in fresh air,then connecting it to a heating unit that may becausing negitive pressure because of a leaking return system is pointless .

As for your fresh air kit? I would ask excactly what it is.

This is some real fun and exciting stuff.

Its actually physics

Its information that has been around forever

What we call absolute facts

High pressure always goes to a low pressure

heat always travels to an absence of heat

Warm air rises

cool air sinks

Spent some time in a class at the HBPA show in Uta that covered this stuff.

Its stuff we have been dealing with in the HVAC feild for years. And it was so cool to see the people from the hearth industry scratching there heads trying to soak this stuff in. I think we are going to see more and more of it in the hearth industry, After all whos left holding the bag when a chimney is puffing back? We had better understand this pressure thing.

I wont take this post off topic but this is what the manufacturers should also be adressing in there installation manuals.

I also think that the NFI should be covering this material in there certification courses

 

[begreen]

Nice info fastrac. I've never been a fan of exterior chimneys. It would be great to consolidate this into a wiki. Maybe two - one on the physics and woes of an uninuslated exterior chimney and another on finding hidden pressure imbalances in the home.

 

[Roospike]

The candles might not be enough heat for a lot of these...and then the next thing you know, the house has black soot on the walls because of the candles burning.

..

I agree that the candle is not going to be for every one , its just something that worked for him. The issues should be addressed to fix the problem and the candles and other ideas are a temporary fix at best.

I do not agree that burning candles in your wood stove are going to blacken your walls with soot but that's just IMO .

 

[fastrac]

The candles might not be enough heat for a lot of these...and then the next thing you know, the house has black soot on the walls because of the candles burning.

..

I agree that the candle is not going to be for every one , its just something that worked for him. The issues should be addressed to fix the problem and the candles and other ideas are a temporary fix at best.

I do not agree that burning candles in your wood stove are going to blacken your walls with soot but that's just IMO .

Another topic entirely

Candels are NASTY. Most of them destroy homes with soot. A greasey ,waxy soot

This is something that Hearth folks are often left holding the bag on also

" I have soot all over my home from the new stove you installed"

Before i start to diagnoise it on the phone I take a ride over with a folder of information. I llok around the home and count the candels then give them the information

Way too much to information to go into on this post, But candle are a problem in the home

Do a google search of

" candle soot damage "

You are probably going to be suprized

 

[begreen]

fastrac, we have an old farmhouse that got a yuppie attack in the mid-80's. They installed many recessed cans that are now the source of air infiltration on windy days and heat loss. What are my options for mitigating the effect without a ceiling tear out? Would adding a lens (the milky white variety) block the heat loss, wind infiltration? Could I install compact fluorescents and then insert a clear acryllic plug that fits tightly into the trim ring? Other options?

PS: Where are you located?

 

[fastrac]

fastrac, we have an old farmhouse that got a yuppie attack in the mid-80's. They installed many recessed cans that are now the source of air infiltration on windy days and heat loss. What are my options for mitigating the effect without a ceiling tear out? Would adding a lens (the milky white variety) block the heat loss, wind infiltration? Could I install compact fluorescents and then insert a clear acryllic plug that fits tightly into the trim ring? Other options?

PS: Where are you located?

You would have to find out the manufacturer of your lights, From there see what covers they are rated for. Although it seams simple enough to go to the retailer to find a cover large enough to cover it. But the problem is ,if they are not listed with covers then they should not be used with covers.

Beside being in the hvac business I am also a licenced electrical contractor. We only quote the sealed box recessed lights (Soon to be required by N.E.C. ) on all of our jobs. Unfortunately my competitors don't so I am normally higher then most, Not because i get to put more money in my pockets, Mostly because we are using higher quality products


As for where I am located I am about 40 minutes north of NYC