Double Wall vs. Triple Wall Class A Chimney

[Obadiah]

As a firefighter, I would encourage anyone looking to do an exterior Class A chimney installation to first make sure they go with a chimney that meets Canadian specs as the pipe is better insulated, some is even 2" thick. The new DuraVent DuraPlus HTC meet these specs and is vast improvement over DuraPlus which I wont sell to anyone north of Florida. Next go to the NFPA website, (National Fire Prevention Association) website and see if you can find the National Statistics for home fires related to chimneys. I don't have that info in-front of me and were swamped so I don't have time right now to look it up, maybe latter. Saw the data a year or so ago and was amazed at how many home fires we caused by wall thimbles verses straight up through the roof. They attributed it to the fact that the creosote builds in the horizontal pipe in the wall and the fact that the smoke has to do a 180 degree turn before it goes up the chimney which is cold when you first fire the stove and will condensate as it heats up creating creosote issues. When a chimney fire does start, the risk of the elbow inside of the home melting increases with every minute the chimney is burning, once it burns through you literately have a rocket engine inside your home burning from both ends at over 2000 degrees!! A sure fire way to burn a house down before the local fire dept can respond. I will no longer do any through the wall installations or those types of chimney sales unless there is no other way to do the job, then I spend a great deal of time with the customer teaching them how to properly clean their own chimney, if they wont clean their own chimney, I'll pass on the sale. The worst thing that generally will happen to a through the ceiling type of installation during a chimney fire is the chimney cap melts and falls off and rolls off the roof starting a fire in the shrubs on the outside of the house, a far better option if your have to have a chimney fire in my opinion. This is because there is not restriction in the pipe and the flames, sparks and heat take the path of least resistance and blow out the top of the chimney stack, the pipe does not get as near as hot as one with elbows which trap the heat. Most folks would rather go through the wall because they are afraid of a rood leak around the flashing. In thousands of installations i have done in my career I have never had a call back for that problem. A properly install roof flashing will not leak, even installed in a metal roof with heavy snow loads. Being in the Hearth business over 33 yrs. now looking back I can safely say that 90% of the folks that call me with smoking and drafting issues had some form of an exterior installation. I just had a customer called with questions so I did a quick search and as usual my friends here at Hearth.com were already on it here on this tread, so I thought I'd drop in add my two cents and say hi! Thanks for all you guys do to help folks get a safe install, the firefighters of the world applaud you!
Blessings!

 

[johnstra]

Woody - I sent you a pm.

 

[bag of hammers]

A properly install roof flashing will not leak, even installed in a metal roof with heavy snow loads.

+1

Of 2 installs at my place - the 1st (a DIY - me, @ 14 years ago) never had any leaks - bullet proof - the 2nd install ("pro" roofers) leaked by year # 3. It looked pretty, but a sanity check with a few experienced roofers on how to fix it led me to know how they screwed it up to begin with.

Kudos to you for doing quality work on peoples' houses (and the firefighter work you guys do).

 

[Johnny G82]

Obadiah, I appreciate your caution about being fire safe and cleaning the chimney regularly, but are you saying that you wouldn't trust a properly installed class a chimney through the wall installation with the standard Duravent Duraplus system?

I have to admit, your post is making me nervous about my plan to use a through the wall exterior chimney installation with this product

 

[Obadiah]

Obadiah, I appreciate your caution about being fire safe and cleaning the chimney regularly, but are you saying that you wouldn't trust a properly installed class a chimney through the wall installation with the standard Duravent Duraplus system?

I have to admit, your post is making me nervous about my plan to use a through the wall exterior chimney installation with this product

Johnny,
I'm sorry about making you nervous, but yes, I would never do a through the wall install unless there is no other way, then I would definitely choose a different pipe if the installation was anyplace that can see a 30 degree or lower temperature. DuraPlus is an outdated triple wall air cooled, poorly insulated chimney that only carries a UL 103 rating and has been regulated to the BIG BOX STORES and is not sold by any chimney pros I know in the North Country. We were given DuraTech by DuraVent as our Pro Grade Chimney, which carries a UL 103 HT and ULC S604.rating and is only supposed to be sold by authorized dealers and installed professionally. This may be replaced again and the box stores will receive the DuraTech as the DuraPlus is getting a bit long in the tooth even for those stores which are switching to the more modern Super Pro Pipe and Metalbestos pipe, which is a low grade Solid Pac Class A Chimney but better than DuraPlus in my opinion. Selkirk does offer a higher grade professional pipe for their chimney pros. My best guess is that we'll get upgraded to a better grade of pipe so DuraVent can remain competitive in the Big Box game and we'll get DuraPlus HTC which is tested to Canada's stringent 2100 degree F standard, ULC S629. and DuraTech Canadian which carries a ULC S629, ULC S604 and ULC S610 rating which is superior to anything else that DuraVent offers. By the way DuraVent has been purchased again and is now owned by M & G Group headquartered in the Netherlands. The good news is they also purchased Security Chimney which is excellent Canadian pipe and I'm sure that will be great for DuraVent. In fact the new DuraTech Canadian pipe shares many similarities to Secure Temp by Security. I personally prefer to use only chimney that meets the tougher Canadian specs in my own installations as were in Montana where we can see 50 below. My favorite is Security GX which is only available in 7". We sell a lot of pipe because we offer complete chimney design services and tech support and competitive pricing with the Hearth Appliances we offer as a package deal. One Stop Shopping with excellent support and service before, during and after the sale. With so many folks in the chimney pipe game now, like Lowes and Home Depot and some online companies that are selling chimney pipe for less than guys like us can buy it for, this is the only way we can remain competitive. There are still enough pros left out there that the chimney manufactures know they have to help us out somehow or we'll all be put out of business. The guys that really care about safety and buying the best pipe will continue to buy from companies like Obadiah's and the rest will run to Lowes and HD and continue to call us for advice and parts that the box stores don't offer to complete their installations. When will folk understand that the big guys are killing the little guys and when were all gone the Big Guys will raise the prices and you wont get any service from anyone and pay through the nose for everything? Fortunately the Big Guys have stayed out of stoves as they have gotten their butts sued off for unbelievable incompetency but they are getting brave again and the suppliers are getting greedy. Hope this helps answer your questions, perhaps someone else can take the time to break down what all the UL listings actually mean in terms of burn rates and testing times, once folks understand that, it all becomes very clear what I am saying and how much better the Canadian pipe is verses our stuff. I still have a bunch of quotes to do for folks yet tonight. Blessings!
Here are your references (broken link removed to http://duravent.com/ProductCategory.aspx?c=8)
(broken link removed)
(broken link removed)
(broken link removed to http://ulstandardsinfonet.ul.com/scopes/)
http://www.nfpa.org/
http://www.ul.com/global/eng/pages/

 

[oldspark]

Since dura plus has insulation and an air gap I was under the inpression it was a good product, you are saying it is not, much better then the triple wall with no insulation for sure
I edited my post a little, I guess there is more then one duraplus products.
Duraplus triple wall-UL Listed to UL 103HT (MH7399).
Sure as hell dont want to promote a product that is not as good as the double wall insulated.
I agree with through the wall not as good a way to do it but as BWS states done right it should be fine but Obadiah's advice is not to be taken litely.

 

[Backwoods Savage]

Obadiah, I appreciate your caution about being fire safe and cleaning the chimney regularly, but are you saying that you wouldn't trust a properly installed class a chimney through the wall installation with the standard Duravent Duraplus system?

I have to admit, your post is making me nervous about my plan to use a through the wall exterior chimney installation with this product

Johnny, Obadiah has some good ideas and probably more experience than I. However, I will say that I've known several folks with through-the-wall installations and none have had a problem if it was installed correctly. We have had a through-the-wall setup for about 34 years and have never had a problem. But I can see where some could have a problem especially if they insist in burning in the old ways and not drying their wood properly. That is the cause of creosote and creosote is an accident waiting to happen. We burn wood that has been in the stack 3 years or more so we simply do not get any creosote in our chimney. I'll add that our chimney has not seen a brush for 4 years now and it does not need one either. Another point is to have the horizontal section have some rise to it. Code calls for 1/4" rise per foot of horizontal. We went 1/2" or more. Result? No problems.

I have seen some very poor setups. That is, some with nor rise in the horizontal and some with an actual decrease! Bad for sure.

 

[Obadiah]

If you have to go through a wall in a Northern Climate and there is no other way to do it, you should enclose the pipe in an insulated chase to keep it as warm as possible. Here are some picture that of our customers chimney installations that I think represents a good way to do this type of install.

 

[knowledgeseeker]

Hi there, I've never posted anything before but here goes. I am preparing to have installed a new Monessen/Majestic Biltmore SB44HB woodburning fireplace and have been trying to educate myself on the whole process. As per manufacturer requirements, the chimney system components used for installation must be those tested/made for this c / UL / us listed unit – specifically CF11 chimney piping in this case, which were ordered at the same time with the unit. I did not realize initially that the piping did not come with mineral insulation between its layers (nor is it stainless steel I think), and so have been researching double wall piping to address my concerns. From what I understand, the CF11 appears to be double wall air cooled piping - however there is also a 2” clearance installation requirement for the chimney ... does this make it air insulated chimney piping?

Also, I live in a northern/cold climate and am trying to ensure install is done with optimal conditions with all safety precautions being observed of course. As such :

a) the fp unit, chimney/chase is located on exterior wall but within the heated building enveloppe on the main floor of the house
b) surrounding exterior walls have been insulated as per manufacturer recommendations/ with Roxul mineral wool insulation
c) sufficient and proper chimney height and rise are confirmed
d) chimney trajectory not perfectly straight but goes as straight up as possible with only one small offset/30 degree bend so as to maximise draft
e) cold climate kit will be installed as well as combustion air kit
f) attic insulation shield and firestops at all floor/ceiling levels

Questions:

1) Can anyone confirm that the CF11 piping is indeed air insulated piping?

2) If not, or perhaps in any event, is there anything further to be done to increase insulation while it is still possible/space is accessible or to reduce chances of any condensation or corrosion of the piping over the long term? (is it permitted or advisable and is there any benefit to adding a ceramic insulating blanket to the outside of this venting within the chimney chase?)

3) As this is a new construction, should I try to incorporate a small access door on one of the interior house walls of the chase on the second level (top floor) to permit access and visual examination of the inside of the chase/exterior of the chimney for the future or is this really unecessary?

All recommendations are welcome. Thanks in advance.

 

[Obadiah]

Questions:

1) Can anyone confirm that the CF11 piping is indeed air insulated piping?

2) If not, or perhaps in any event, is there anything further to be done to increase insulation while it is still possible/space is accessible or to reduce chances of any condensation or corrosion of the piping over the long term? (is it permitted or advisable and is there any benefit to adding a ceramic insulating blanket to the outside of this venting within the chimney chase?)

3) As this is a new construction, should I try to incorporate a small access door on one of the interior house walls of the chase on the second level (top floor) to permit access and visual examination of the inside of the chase/exterior of the chimney for the future or is this really unecessary?

All recommendations are welcome. Thanks in advance.

Greetings Knowledge Seeker, you have come to the right place for all things Hearth related.
1. Unfortunately what you have there is Air-cooled Chimney and it is tested to a lesser standard of Class A.
2.There is nothing you can or should do to change the way the pipe is designed to function. If you do you run the risk of causing a fire.
3.I always put an access panel in every chase I build as I am also a professional firefighter and do insurance investigations on the side after the home has caught fire because of the fireplace installation. You would not believe how many air cooled chimneys I have seen come apart with builder box fireplaces. There are installers out there during the building boom of a few years ago that would brag that they could install 4-5 of those fireplaces in a day! Of course quality was not the focus. If your installing it yourself you will be more careful snapping the chimney together. Being able to inspect any chimney up close and personal is a great idea, my clients would have me service their fireplaces every year and I would clime into the chase and clime up from fire-stop to fire-stop where I would install a trap door to inspect each seam to make sure there was no black spots, or separations. Many times a chimney will come apart later if not properly connected at the seams when the chimney sweep shows up to clean the chimney. Some don't seem to enjoy their jobs and can get pretty violent up there ramming the chimney brush up and down especially if there are any offsets in the chimney system. They can and do come apart if they are not properly supported.

You have what is known in the business as a "Builders Box" and the fireplace will suck more heat out of your home than it will put in. You mentioned your in a cold climate, if your expecting this fireplace to reduce your heating bill it will actually do the opposite. http://www.woodstoves.net/majestic/wood/biltmore-44-sb-fireplace.htm It is designed to burn hot and fast and is not subject to the same EPA our UL regulations as heat producing fireplaces because you'll get tired of feeding it wood before you would every try to use it to heat with, you cant turn it down low enough for an all night burn, so it is just for decoration, that is it. The chimney is Air Cooled because the stove burns hot and fast and does not make much creosote or smoke, unlike a fireplace that you can shut down for an all night burn like a http://www.woodstoves.net/osburn/wood/stratford.htm which in my humble opinion is one of the best fireplaces on the market for the price. You can use a wide verity of insulated Class A Chimney with the Stratford. It is made by SBI in Quebec, The Osburn Stratford has a lifetime warranty and produces 75,000 BTUs of usable heat without a blower because of its convection design. It will heat up to 2000 Sq. Ft and takes a 21" log.

My personal favorite wood burning fireplace for Northern climates is the BIS Tradition also made in Canada in Quebec, well until Lennox bought them which is a very unfortunate thing, in my opinion. I have been selling and installing BIS fireplaces for almost 20 yrs now and they were the best fireplace made for heating. Built very well with high quality steel they can be burned with the doors open for the ambiance and snap crackle pop, or closed for heating efficiently with wood. As with all Hearth appliances the chimney system is the engine that drives the appliance just like the engine drives the vehicle. You would never put a Yugo engine in a Beamer nor should anyone install an air cooled chimney on a high quality fireplace. There are several high end fireplaces that only come with air cooled chimney, which is a total joke in a cold climate, like Ontario where you live or Montana where I live. I will not sell a high end fireplace that is used for heating North of the Mason Dixon Line. What happens is when you turn the fireplace down at night for a long overnight burn the fireplace does not burn as hot, an air cooled chimney can cool down to the point that it will quit drafting. If someone turns on a bathroom fan, or worse yet a home with more than one that is well constructed and tight, negative pressure will build in the house pulling air down the chimney and you'll wake up to a home full of smoke, pretty scary if you don't realize what is going on. I have seen that scenario happen before and hear horror stories from folks who call me later and say, "Woody you were right I should have listened to you, that $1000 dollars I saved on the fireplace just cost $20K in smoke damage and my wife is not a happy camper."

The BIS Tradition is available with 7" Security GX chimney which is 2" thick solid pack pipe that is designed for the BIS Tradition and Canadian Arctic winters. This chimney will burn hotter and draft better than any chimney out there, minus the new M&G DuraPlus HTC which is also 2" thick. There are some other chimneys out there that are 2" thick that are great for cold climates like the Yaak where I live, we can see 50 below. When it gets that cold you have no idea what it is like, steel breaks like glass from being brittle. There are many really cool features with the BIS Tradition, like the Turbo Boost feature which allows you to set the fireplace air control in the morning when you stoke your fire and walk away. It is like leaving the door cracked open for a half hour while the fire reestablishes itself after you reload the firebox with wood. It will automatically over the next couple hours gradually shut itself down to whatever setting you set the fireplace at, low, medium or high burn. No more leaving the door cracked in the morning while you drink a cup of coffee waiting for the fire to get going, only to get a phone call and space the fact the door is open. Off to work you go, up in smoke the wood goes and you come home to a cold house because you forgot to shut the door. Oppps.....

80,000 conservatively rated BTUs and a 30" log make things really nice for cutting your wood, she will keep you and your family warm and cozy in the most extreme climates, the BIS Tradition is my choice in wood fireplaces in cold climates. (broken link removed to http://www.woodstoves.net/security/bistradition.htm)
She even comes in a Compact Edition and is called the BIS Tradition CE she is rated at a conservative 55,000 BTUs and will heat up to 1500 sq. ft. burning 20" logs. She uses 6" Security ASHT chimney which is also great pipe, but not 2" thick.
(broken link removed to http://www.woodstoves.net/security/bistraditionce.htm)

Well I hope I have educated you on fireplaces and the chimney systems that make them what they are. Bottom-line Air Cooled chimney works ok for fireplaces that burn quick and hot, not so much for those that claim to be efficient and get a long burn time, maybe down South they work OK, where you and I live, not so much. I would advise staying clear of them and any dealer that does not know the difference.

Have a Blessed and Prosperous New Year 2014!

 

[knowledgeseeker]

Thank you so much for taking the time to write a thorough and informative response. Your recommendations are much appreciated. I am disappointed to find out that the quality of the chimney piping purchased is not grade A. This confirmed my initial worry (which prompted me to write here) as I saw when it was delivered to the site that it was not insulated like what I had seen before. I wrongly assumed that a more expensive fp model would be paired up with same in piping. However, luckily, the fireplace will not be a main source of heating for the house. It was supposed to be for a back-up heat source in case of a power outage/emergency (although it now appears that I should perhaps not use it in this situation if it will suck out more heat from the house that it can provide!?) and for pleasure. Fortunately, I will have the benefit of a highly efficient water radiant system for the whole house which will permit me to use this fireplace merely for pleasure I suppose - for "hot and fast" burns as you call it and for a decorative purpose. My family and I love the crackle (and subtle smell) of a wood burning fireplace and the family activities which surround it.

That said, safety is paramount. Following what you said:

1- a) are there any special recommendations on installation to ensure that the snapping together of the chimney sections/seal created are as tight and sturdy as possible? I did duly note your comment to provide proper support to the components with special attention to any offsets and avoiding cantankerous chimney sweepers!

b) Any specific spacing recommendations for providing support to the chimney sections above and beyond manufacturer's recommendations?

I will ensure to plan for as many access doors as possible to enable visual inspection of the chimney components.
- - - - - - - - - - - - - - -- - - - - -

This said, I must admit I am now concerned about the possibility of smoke being sucked back accidently into the house. Could you please help me further understand how to avoid this:

As a newly constructed house, the envelope will be tight.

2- a) Will making sure the fire is out in the fireplace before bed (therefore never leaving it alight/alive at night and unattended) ensure that one does not provoke the chimney to cool down to a point where it stops drafting or are there other situations where this can happen (negative pressure in the house?) ?

b) Should I ensure that no fans ever run at the same time as the fp?

I will have an HRV and a dedicated venting system in the bathrooms but have no experience with this yet and am therefore still unclear on the potential impact of its functions on venting and possible "backdrafting"(if that is the correct term). In an ideal world, I would be able to use my kitchen fan which will have about 650CFM, at the same time as the nearby fp, without worrying about "backdraft" ruining the house with smoke! (and also my bath fans for that matter!)

c) should I therefore do a blower test or any other test once all the hvac systems are up and running to ensure that no smoke gets sucked back into the house/ have proper pressure in the house (although I don't know what that would be! non negative pressure?) and am I confusing 2 concepts here?

- - - - - - - - - - - - - - - - - - - - - - - - -
3) Apart from an annual visual inspection of the chimney connections to ensure there are no black spots or separations, if the type of use and burning I will get from my fp is hot and fast therefore resulting in little creation of creosote or smoke, coupled with moderate use during the winter, how often should chimney cleaning be done specially if cleaning (albeit aggressive cleaning) can contribute to loosening the seals between components?

Thanks again for your expert advice on these issues. It is much appreciated. Best wishes for the New Year as well!

 

[Obadiah]

[
1- a) are there any special recommendations on installation to ensure that the snapping together of the chimney sections/seal created are as tight and sturdy as possible? I did duly note your comment to provide proper support to the components with special attention to any offsets and avoiding cantankerous chimney sweepers!
Depending on the brand of Class A Pipe, when you put it together it will assemble differently, Air Cooled chimney snaps together and is pretty much impossible to get apart once assembled properly. Other Class A Solid Pack Pipe twist locks together and can be unlocked and taken apart by simply unscrewing like a lid on a jar, a couple screws will prevent it from coming unscrewed.
b) Any specific spacing recommendations for providing support to the chimney sections above and beyond manufacturer's recommendations?
Follow the instructions carefully and make sure you have what is specified in the manual. Adding extra does not hurt anything.
I will ensure to plan for as many access doors as possible to enable visual inspection of the chimney components.
- - - - - - - - - - - - - - -- - - - - -

This said, I must admit I am now concerned about the possibility of smoke being sucked back accidently into the house. Could you please help me further understand how to avoid this:

As a newly constructed house, the envelope will be tight.

2- a) Will making sure the fire is out in the fireplace before bed (therefore never leaving it alight/alive at night and unattended) ensure that one does not provoke the chimney to cool down to a point where it stops drafting or are there other situations where this can happen (negative pressure in the house?) ?
Most fireplaces come with outside air kits, make sure they are properly installed and not on the downwind side of the house where prevailing winds will create negative pressure and cause a problem. I would not say that making sure that you have a hot fire when you go to bed with a good bed of coals will help keep the fireplace hot enough to burn through the night. Stoke the fire a couple hours before you turn in, never stoke the fire and in a half our or less shut the fireplace down for the night. The BIS Tradition and Lennox Montecito Estate have built in timers that control the air intake and prevent having to worry about turning the fireplace down too low before the fire is fully established for the evening or day.
b) Should I ensure that no fans ever run at the same time as the fp?
A very simple way to remedy this problem is to put all blowers on timers so they can run non stop, in some areas this is required by code.
I will have an HRV and a dedicated venting system in the bathrooms but have no experience with this yet and am therefore still unclear on the potential impact of its functions on venting and possible "backdrafting"(if that is the correct term). In an ideal world, I would be able to use my kitchen fan which will have about 650CFM, at the same time as the nearby fp, without worrying about "backdraft" ruining the house with smoke! (and also my bath fans for that matter!)
Installing a whole house fresh air system that reclaims 80% of the heat before it exhaust it by heating the air it pulls back in is a balanced system, it does not pull in more air than it exhaust. I run a BROAN system with a built in HEPA filter in my place because my wife is hyper chemically sensitive and has Asthma to boot. It helps keep the home full of fresh mountain air from outside. Homes today made of OSB, furniture made of particle board, carpenting, and so on all emit poisonous gases like formaldehyde which over time take their tolls on our bodies and make us toxic. Our home has no carpets, no particle board furniture and we have ceramic tile floors laid with thinset mortar, real wood furniture, and even the paint on the wall is special clay based natural paint. To balance the air pressure inside the house I have a special butterfly valve installed that equalizes the pressure and if negative pressure builds in the house it will open and equalize it. We use Ionic, Ozone and Ultraviolet air purification systems that eliminates the need for air being exhausted except for near the cooking range. That fan is only turned on if someone burns something accidently and it is on a timer too.
c) should I therefore do a blower test or any other test once all the hvac systems are up and running to ensure that no smoke gets sucked back into the house/ have proper pressure in the house (although I don't know what that would be! non negative pressure?) and am I confusing 2 concepts here? If you hook up a negative pressure whole house tester, I can guarantee you'll pull smoke in as the mechanical fan will overcome the natural draft every time. Yes your confusing that test that with something else. Simply make sure the timers are installed on the exhaust blower and you have outside air hooked up to both the fireplace and the air cooled chimney so it is pulling the air into the base of the chimney through the vent pipe connected to the outside. This keeps the pipe from overheating, when its cold it makes the internal chimney sweat and condensate building creosote faster. It is like walking outside in the summer with a glass of ice water, or cracking an ice cold beer. But at least it balances the system and keep the cold air from filling the chimney chase cavity and making the fireplace condensate and rust. Having the outside combustion air coming into the firebox will balance the air pressure in the house where the fireplace is and it will pull the combustion air in from the path of least resistance. Make sure you put a air trap in the flex pipe to trap the air so it does not leak from the fireplace into the house. If you have ever sat on the hearth of a prefab fireplace and felt cold air coming in from the lower vent under the firebox, that is why, the installer ran the flex vent straight from the outside to the fireplace and cold air is coming inside through the pipe. Put the outside vent lower than the base of the fireplace also helps prevent this, putting the vent higher means the cold air will come in and go down. Cold air goes down warm air goes up.

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3) Apart from an annual visual inspection of the chimney connections to ensure there are no black spots or separations, if the type of use and burning I will get from my fp is hot and fast therefore resulting in little creation of creosote or smoke, coupled with moderate use during the winter, how often should chimney cleaning be done specially if cleaning (albeit aggressive cleaning) can contribute to loosening the seals between components?
If the chimney pipe is properly installed it will never come loose so I would not be too concerned. How often the chimney will need cleaning will depend a lot on the firewood your burning, hire a CSIA Chimney Professional to come in and check out your chimney for you, they will set you up on a schedual and clean the chimeny and inspect it for you as needed. http://www.csia.org/ Go to the website and enter your zip code and they will give you a list of chimney pros near you.

Thanks again for your expert advice on these issues. It is much appreciated. Best wishes for the New Year as well!
Sorry it took so long to get back to you, we've been gone on vacation cruising the Caribbean while most of the country was experiencing record cold temps. When we got back we have been busy playing catch up trying to respond to folks need for heat! Strange year, here in Montana we normally have about 4-6 feet of compacted snow on the ground and about 20' up on the nearby peaks. Our temps are normally in the low teens and can drop as low as 50 below, we've had balmy temps and have 1" of snow on the ground here! Down South folks are telling me they are in the single digits when normally they would be in the 40-50s, strange weather this year.

/QUOTE]

 

[Obadiah]

Thank you so much for taking the time to write a thorough and informative response. Your recommendations are much appreciated. I am disappointed to find out that the quality of the chimney piping purchased is not grade A. This confirmed my initial worry (which prompted me to write here) as I saw when it was delivered to the site that it was not insulated like what I had seen before. I wrongly assumed that a more expensive fp model would be paired up with same in piping. However, luckily, the fireplace will not be a main source of heating for the house. It was supposed to be for a back-up heat source in case of a power outage/emergency (although it now appears that I should perhaps not use it in this situation if it will suck out more heat from the house that it can provide!?) and for pleasure. Fortunately, I will have the benefit of a highly efficient water radiant system for the whole house which will permit me to use this fireplace merely for pleasure I suppose - for "hot and fast" burns as you call it and for a decorative purpose. My family and I love the crackle (and subtle smell) of a wood burning fireplace and the family activities which surround it.

That said, safety is paramount. Following what you said:

1- a) are there any special recommendations on installation to ensure that the snapping together of the chimney sections/seal created are as tight and sturdy as possible? I did duly note your comment to provide proper support to the components with special attention to any offsets and avoiding cantankerous chimney sweepers!

b) Any specific spacing recommendations for providing support to the chimney sections above and beyond manufacturer's recommendations?

I will ensure to plan for as many access doors as possible to enable visual inspection of the chimney components.
- - - - - - - - - - - - - - -- - - - - -

This said, I must admit I am now concerned about the possibility of smoke being sucked back accidently into the house. Could you please help me further understand how to avoid this:

As a newly constructed house, the envelope will be tight.

2- a) Will making sure the fire is out in the fireplace before bed (therefore never leaving it alight/alive at night and unattended) ensure that one does not provoke the chimney to cool down to a point where it stops drafting or are there other situations where this can happen (negative pressure in the house?) ?

b) Should I ensure that no fans ever run at the same time as the fp?

I will have an HRV and a dedicated venting system in the bathrooms but have no experience with this yet and am therefore still unclear on the potential impact of its functions on venting and possible "backdrafting"(if that is the correct term). In an ideal world, I would be able to use my kitchen fan which will have about 650CFM, at the same time as the nearby fp, without worrying about "backdraft" ruining the house with smoke! (and also my bath fans for that matter!)

c) should I therefore do a blower test or any other test once all the hvac systems are up and running to ensure that no smoke gets sucked back into the house/ have proper pressure in the house (although I don't know what that would be! non negative pressure?) and am I confusing 2 concepts here?

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3) Apart from an annual visual inspection of the chimney connections to ensure there are no black spots or separations, if the type of use and burning I will get from my fp is hot and fast therefore resulting in little creation of creosote or smoke, coupled with moderate use during the winter, how often should chimney cleaning be done specially if cleaning (albeit aggressive cleaning) can contribute to loosening the seals between components?

Thanks again for your expert advice on these issues. It is much appreciated. Best wishes for the New Year as well!

Sorry for the delay, for some reason the first reply never posted properly.
Here are the answers to your questions.
1- a) are there any special recommendations on installation to ensure that the snapping together of the chimney sections/seal created are as tight and sturdy as possible? I did duly note your comment to provide proper support to the components with special attention to any offsets and avoiding cantankerous chimney sweepers!
b) Any specific spacing recommendations for providing support to the chimney sections above and beyond manufacturer's recommendations?
Depends on the brand of chimney, some require additional screws installed to meet UL, so I can not give an answer other than the pipe must be fully engaged male end down, female end up, so the creosote will run down inside the joints and not on the outside of the chimney pipe. If the seams are dripping creosote then the pipe is installed upside down! Unbelievable how many times this is the case....Offsets are where the issues generally also arise, so even though the joints are properly joined and secured, the weight of the pipe above will cause the joints to open up over time, if not properly supported. Add a angry chimney sweep and something will come apart eventually......so make sure each offset is properly supported with the elbow straps the pipe manufacture offers, or even plumbers tape if your on a job where there are no supports. Always go overboard on supporting offsets against gravity pulling down on the chimney installed above the offset, as well as laterally so the chimney does not move around which causes stress to each joint. This is how they come lose 20 yrs later, the screws work out first and then the chimney will begin to unspin itself as it is slopping around inside the chase. By code there needs to be a firestop at each floor level inside the chase so the chase itself does not act like a chimney in the event of a fire starting inside the chase, or burning through into the chase. These firestops also act as stabilizers and places to attach support brackets and such, which lock the pipe in place and prevent the pipe from moving or spinning lose.
2- a) Will making sure the fire is out in the fireplace before bed (therefore never leaving it alight/alive at night and unattended) ensure that one does not provoke the chimney to cool down to a point where it stops drafting or are there other situations where this can happen (negative pressure in the house?) ?
It will definitely help not to have a potential issue by making sure the fire is almost out when you turn in for the night. You'll have an outside air kit on your fireplace which will suck combustion air in from a 3 or 4" aluminum flex tube connected to a inlet on the outside of the chimney chase that will feed the fireplace fresh air as long as it is open and air can flow. Unfortunately when the cold air comes into this tube it builds condensation. If the tube is dipped down it will collect water and begin to sag and act like a drain trap, either restricting or blocking off the air flow as the water continues to collect. If the fireplace is not being used over the summer, the water evaporates and everything works great. Took a long time to get that one figured out. Anyhow make the loop go up not down so it wont trap water.