Chimney pipe sizing

[bjvista]

Hi everyone,

I hope this is in the correct forum. I have a wood burning fireplace I've installed in a house I just built. I installed one of these: https://www.efireplacestore.com/sup-wrt2036wsi.html

Now when I say installed, it's only mounted in the wall opening so far. I now have to figure out the chimney pipe setup. I live in Central America (i know i know, a fireplace in central hot america) so we won't do very hot or frequent fires. 10-15 small fires every winter. My wife's dream has always been a fireplace in the bedroom which is why I installed it.

Yes I built the house to US and/or International Code, but there is no inspection or homeowners insurance here. The roof is metal, the walls are cement and block. I don't plan on doing this 100% the proper way I would back home in the States. I just need it to have enough draft to burn a fire when needed. It's only for ambiance and not heating the house or room.

The fireplace has an 8" open on the top of it. I need to rise about 8' feet to penetrate the roof and need to angle over about 7'. Then I'll come out the roof 4' or 5'.

My question is, can I just use 8" flexible stainless pipe, wrap it with insulation to the roof line? The chimney I'll figure out after. If I can use flex, can I reduce to 6"? I have to ship the flex from the States to here which is not cheap. So I'm trying to see if I can use flex if I can reduce to 6".

I'm looking at this on amazon: amazon link

and then I'll wrap it with insulation 1/4" or 1/2" if needed.

Summary:
Metal roof, cement house, no combustibles within 12"
Can a chimney flex pipe be used?
Can I reduce from 8" to 6"?
Is insulation needed and if so 1/4" or 1/2"?

I know I'm probably missing a bunch of info so if you have questions I'm all answers.

 

[bholler]

Hi everyone,

I hope this is in the correct forum. I have a wood burning fireplace I've installed in a house I just built. I installed one of these: https://www.efireplacestore.com/sup-wrt2036wsi.html

Now when I say installed, it's only mounted in the wall opening so far. I now have to figure out the chimney pipe setup. I live in Central America (i know i know, a fireplace in central hot america) so we won't do very hot or frequent fires. 10-15 small fires every winter. My wife's dream has always been a fireplace in the bedroom which is why I installed it.

Yes I built the house to US and/or International Code, but there is no inspection or homeowners insurance here. The roof is metal, the walls are cement and block. I don't plan on doing this 100% the proper way I would back home in the States. I just need it to have enough draft to burn a fire when needed. It's only for ambiance and not heating the house or room.

The fireplace has an 8" open on the top of it. I need to rise about 8' feet to penetrate the roof and need to angle over about 7'. Then I'll come out the roof 4' or 5'.

My question is, can I just use 8" flexible stainless pipe, wrap it with insulation to the roof line? The chimney I'll figure out after. If I can use flex, can I reduce to 6"? I have to ship the flex from the States to here which is not cheap. So I'm trying to see if I can use flex if I can reduce to 6".

I'm looking at this on amazon: amazon link

and then I'll wrap it with insulation 1/4" or 1/2" if needed.

Summary:
Metal roof, cement house, no combustibles within 12"
Can a chimney flex pipe be used?
Can I reduce from 8" to 6"?
Is insulation needed and if so 1/4" or 1/2"?

I know I'm probably missing a bunch of info so if you have questions I'm all answers.

Flex pipe is a liner that is meant to go inside a chimney not serve as a chimney so no you can't use it in this application you need to get the chimney pipe that is specified for your fireplace and no you can't reduce

 

[bjvista]

Flex pipe is a liner that is meant to go inside a chimney not serve as a chimney so no you can't use it in this application you need to get the chimney pipe that is specified for your fireplace and no you can't reduce

Thanks, bholler, I kind of knew this would be the answer....but is there any reason why using a liner would not work? I know it's not code to have a pipe hanging there without a chimney around it. I would have a chimney after penetrating the roof. This liner would be located in a 20" wide by 10' long gap between to 6" cement walls.

My question isn't so much of "is this the correct way", it's more of is there any reason this wouldn't work?

 

[bholler]

Thanks, bholler, I kind of knew this would be the answer....but is there any reason why using a liner would not work? I know it's not code to have a pipe hanging there without a chimney around it. I would have a chimney after penetrating the roof. This liner would be located in a 20" wide by 10' long gap between to 6" cement walls.

My question isn't so much of "is this the correct way", it's more of is there any reason this wouldn't work?

I can't answer your question with anything but the correct way that I know is safe.

 

[bjvista]

I can't answer your question with anything but the correct way that I know is safe.

Thanks. I understand. Can you tell me what is unsafe or the risks of an installation like that? I'm just trying to figure out my options. I'm in a 3rd world country so my nearest HomeDepot or big box store is thousands of miles away.

 

[bjvista]

And please know I'm not trying to be a jerk or be stubborn. Prior to living here now for 15 years I was born and raised in the States. I was a contractor so have plenty of construction knowledge but have zero knowledge about fire places. My house here that I recently built is the strongest house in the village where we live because it's built to code.

I guess I'm just trying to figure out the risk of using a liner in my situation.

 

[Sailrmike]

Liners are only tested in masonary fireplace applications. That is the only place that they should be used. You are risking burning your home down and possibly injuring or killing yourself and family members by using a liner the way you describe. Use class a chimney pipe or abandon the project.

 

[ABMax24]

If your going to ignore code and just install something then I would be using something like 8" sch40 pipe. You'll never breach that even with the hottest of chimney fires. Surely you can find something like this locally. But don't use galvanized material.

That being said you still need to find a way to keep combustibles far enough away from it to prevent from catching fire. In this case I'd be treating it like single wall stove pipe and keep all combustibles a minimum of 18" away.

Keep in mind this is what I would consider. I'm not saying it is safe or recommended.

 

[bholler]

If your going to ignore code and just install something then I would be using something like 8" sch40 pipe. You'll never breach that even with the hottest of chimney fires. Surely you can find something like this locally. But don't use galvanized material.

That being said you still need to find a way to keep combustibles far enough away from it to prevent from catching fire. In this case I'd be treating it like single wall stove pipe and keep all combustibles a minimum of 18" away.

Keep in mind this is what I would consider. I'm not saying it is safe or recommended.

I have seen lots of failed schedule 40 "chimneys".

 

[ABMax24]

I have seen lots of failed schedule 40 "chimneys".

Honestly I'd like to see pictures of those. Are they due to corrosion or rust?

8" sch40 pipe is 5/16" thick, it's commonly used around here for directly fired fire tubes for all kinds of oilfield equipment. Failures can occur but usually due to lack of maintenance and corrosion.

 

[bholler]

Honestly I'd like to see pictures of those. Are they due to corrosion or rust?

8" sch40 pipe is 5/16" thick, it's commonly used around here for directly fired fire tubes for all kinds of oilfield equipment. Failures can occur but usually due to lack of maintenance and corrosion.

Yes usually corrosion and usually at the base. But I have seen holes directly across from the crock and even one with a split about half way up. Granted most chimneys like that are abused and not really maintained

 

[bjvista]

Yes usually corrosion and usually at the base. But I have seen holes directly across from the crock and even one with a split about half way up. Granted most chimneys like that are abused and not really maintained

Thanks for the info everyone. If the concern is fire then that should easily be avoided. I have a metal roof, metal purlin rafters and cement walls. The closest combustible is my bedroom door 20" away. My biggest concern is creosote. So if I burn dry non-resinous wood I should be able to avoid that.

 

[bholler]

Thanks for the info everyone. If the concern is fire then that should easily be avoided. I have a metal roof, metal purlin rafters and cement walls. The closest combustible is my bedroom door 20" away. My biggest concern is creosote. So if I burn dry non-resinous wood I should be able to avoid that.

How do you plan on attaching all of these parts together that were never designed to work together? How do you plan on maintaining all of the required cooling air flow?

 

[armanidog]

How cold does it get where you are living?
"Belize has a tropical climate with pronounced wet and dry seasons, although there are significant variations in weather patterns by region. Temperatures vary according to elevation, proximity to the coast, and the moderating effects of the northeast trade winds off the Caribbean. Average temperatures in the coastal regions range from 24 °C (75.2 °F) in January to 27 °C (80.6 °F) in July. Temperatures are slightly higher inland, except for the southern highland plateaus, such as the Mountain Pine Ridge, where it is noticeably cooler year round. Overall, the seasons are marked more by differences in humidity and rainfall than in temperature. " Wikipedia
Would a chimney even have a decent draft in such a climate?
You may be better off having something like a wood fired oven built in with the smoke stack outside. You could have a glass door for the firebox so you could see the fire. Plus you could bake some bread while having a fire.

 

[bjvista]

How do you plan on attaching all of these parts together that were never designed to work together? How do you plan on maintaining all of the required cooling air flow?

The only part not meant to attach is from the appliance to the liner. With both at 8" ID it shouldn't be very difficult to create an airtight seal. For the cooling airflow, that will be supplied by the house. It doesn't get cold here, 60's, possibly 50's if a cold front get's pushed down from the north. The windows will always be open this time of year.

If I had a masonry chimney, that would be the only difference than my current plan which wouldn't change the way they are attached or cool air flows. Is that a correct assumption or am I missing something?

 

[bjvista]

How cold does it get where you are living?
"Belize has a tropical climate with pronounced wet and dry seasons, although there are significant variations in weather patterns by region. Temperatures vary according to elevation, proximity to the coast, and the moderating effects of the northeast trade winds off the Caribbean. Average temperatures in the coastal regions range from 24 °C (75.2 °F) in January to 27 °C (80.6 °F) in July. Temperatures are slightly higher inland, except for the southern highland plateaus, such as the Mountain Pine Ridge, where it is noticeably cooler year round. Overall, the seasons are marked more by differences in humidity and rainfall than in temperature. " Wikipedia
Would a chimney even have a decent draft in such a climate?
You may be better off having something like a wood fired oven built in with the smoke stack outside. You could have a glass door for the firebox so you could see the fire. Plus you could bake some bread while having a fire.

Not cold at all. 60's, possibly 50's maybe but not likely. Your reference is very accurate. I live in Mountain Pine Ridge which is cooler than the islands where I lived for 10 years. I don't think the chimney draft will be a problem. I know of a few other people that have fireplaces (not many here and it's mainly a gringo like me) and draft is not an issue. We do have an oven outside kind of like what you are referring to. Here they are called "fogons" and it's basically an outdoor wood fire grill. Most people cook their beans on it. Some even bake with them. You'd be surprised how tasty a white cake can be with a hint of smoke flavor.

 

[bjvista]

I would just like to say that I appreciate everyone's thoughts so far. When I was a contractor in the States and also with building my house here, I always tend to overbuild and am a firm believer in doing it right the first time so that you don't have to repair later. When I built this house the locals were dumbfounded at the amount of steel rebar I was using. They didn't understand my metal rafter spacing. For example, even though I'm using heavy gauge 2x6 metal purlins I still spaced them on 24" centers. One "local builder" in the village actually told me "steel is cheaper than wood because you can space them 6' apart". A local friend of mine has a 24' wide house and has 4 metal rafter every 6'. Sheesh...

My only concern with my fireplace setup was knowing the dangers of using a liner without a masonry chimney. From what I've read on this site and other sites and research, 1. contact or closeness to combustibles and 2. creosote are my concerns.

For combustible contact, that's an easy one. Metal rafters and cement walls help with that. I'll cut back the spray foam insulation a few feet as well. For creosote, I'll mainly be burning mahogany, purpleheart aka bastard rosewood and possibly ironwood and other hardwoods. These will all be well dried (15% or less moisture content). All of these are flitch or waste from local carpenters and a few nearby wood mills. There's actually a horse powered Mennonite wood mill nearby. I've gotten plenty of wood from them for my concrete form boards. They have a bunch of waste there that is free for the taking.

Once I get my setup installed, I'll update this post with a few pics.

 

[bholler]

The only part not meant to attach is from the appliance to the liner. With both at 8" ID it shouldn't be very difficult to create an airtight seal. For the cooling airflow, that will be supplied by the house. It doesn't get cold here, 60's, possibly 50's if a cold front get's pushed down from the north. The windows will always be open this time of year.

If I had a masonry chimney, that would be the only difference than my current plan which wouldn't change the way they are attached or cool air flows. Is that a correct assumption or am I missing something?

The fireplace you are using is not meant for a masonry chimney that is the difference