Will This Chimney Draw Well ?

[Quincy Fivelos]

We are building a new house that will have one wood burning fireplace indoors and one out. The Indoor unit is planned to be a 42" Isokern. The house is two stories plus attic so from the base of the fireplace to the top of the chimney is approx 34'.

The Chimney plan is currently:



Will the cap be a problem vs pots? Any other thoughts?

We expect to have an ACH50 of about 1 or 0.9. I'm guessing that this fireplace will pull about 600-800 CFM. What is the best way to insure that it draws well? 600 CFM make-up air system? Other?

Thanks,

 

[jetsam]

Do you really want to design a system to pull 800CFM of ice cold air into your house when it's cold out? :/

Wood stoves gained popularity in the 1700s because people were sick of that.

 

[Quincy Fivelos]

Do you really want to design a system to pull 800CFM of oce cold air into your house when it's cold out? :/

Possibly? Alternatives?

 

[jetsam]

Possibly? Alternatives?

Wood stove, modern fireplace. Both actually add heat to the house, and pull far less air.

 

[bholler]

Possibly? Alternatives?

A hogh efficency zero clearance fireplace. That will gove you the look of a fireplace with some actual heat output. And they are usually designed with outside air intakes

 

[Quincy Fivelos]

We want a traditional wood burning fireplace.

 

[bholler]

We want a traditional wood burning fireplace.

Ok just be aware that most of the time open firplaces have a net heat loss. If you are fine with that go ahead

 

[brenndatomu]

Yup, 600-800 CFM up the chimney means 600-800 CFM of makeup air that must be pulled into the house somewhere...and when its good and cold out that means the house is gonna feel cold and drafty. And modern construction methods just won't allow for the kind of air leakage...so then the fireplace will leak smoke into the living space if not allowed enough makeup air.
As others have already mentioned, there is a very good reason that open FP have fallen out of favor.
An HE FP insert is a much better option...and you still have a great view of the fire...and you can still hear it too...also, it can be a much cheaper install also, especially if you are OK with fake stone...which once installed, is very difficult to distinguish from real stone...

 

[bholler]

Yup, 600-800 CFM up the chimney means 600-800 CFM of makeup air that must be pulled into the house somewhere...and when its good and cold out that means the house is gonna feel cold and drafty. And modern construction methods just won't allow for the kind of air leakage...so then the fireplace will leak smoke into the living space if not allowed enough makeup air.
As others have already mentioned, there is a very good reason that open FP have fallen out of favor.
An HE FP insert is a much better option...and you still have a great view of the fire...and you can still hear it too...also, it can be a much cheaper install also, especially if you are OK with fake stone...which once installed, is very difficult to distinguish from real stone...

Well said but for new construction you would not use an insert you would use a fireplace

 

[bholler]

We want a traditional wood burning fireplace.

To minimise heat loss due to an open fireplace and provide enough makeup air you will need a fresh air intake roughly the size of the flue

 

[RobbieB]

Yeah, the new EPA ZC's are just as good as a stove and they weigh as much if not more.

 

[brenndatomu]

Well said but for new construction you would not use an insert you would use a fireplace

Yeah guess I didn't word that very well...

 

[bholler]

Yeah guess I didn't word that very well...

I knew ehat you were talking about but not everyone does

 

[brenndatomu]

To minimise heat loss due to an open fireplace and provide enough makeup air you will need a fresh air intake roughly the size of the flue

So basically the same as leaving a small window open...

 

[bholler]

So basically the same as leaving a small window open...

Yeah pretty much but it could be placed in the firebox or right in front of it

 

[brenndatomu]

Yeah pretty much but it could be placed in the firebox or right in front of it

Barometric window?

 

[maple1]

We want a traditional wood burning fireplace.

Just be aware that a traditional fireplace will not do much if anything re. heating your house - most times, it removes more than it generates. I suspect especially so if it will be moving 6-800 cfm. In Minnesota.

Our fireplace is strictly an ambiance only thing that gets used maybe twice a year. We thought we wanted one also, but likely would not do it again.

 

[Simonkenton]

My fireplace pictured at left is a good heater. You have to have a big outside air intake. Mine is 98 square inches.

 

[bholler]

My fireplace pictured at left is a good heater. You have to have a big outside air intake. Mine is 98 square inches.

No it is a heat producer yes because you have enough of a fresh air supply for it. But it isnt a good heater you will still easily use 4 times the ammount of wood you would use in a stove for the same heat. Yes you can make a fire place heat but it is still at best a century old technology.

 

[bholler]

My fireplace pictured at left is a good heater. You have to have a big outside air intake. Mine is 98 square inches.

Yours is also a completly interior structure unlike the one the op is proposing. That makes a huge difference as well

 

[Ashful]

I used to heat a large old house for periods with three open fireplaces. The one with a fresh air intake actually did a decent job of producing heat without cooling the rest of the house via make-up air draw, but it was a hungry beast that still sent a lot of heat up the flue. The ones without make-up air really caused distant rooms to go cold, as they drew their make up air thru every crevice they could, from each of those rooms not benefiting from their direct heat.

All of them suffered from a common problem, in that you’d have to leave the chimney open 12 hours beyond when they stopped producing heat, when you were ready to let them go out. That’s 600+ CFM of your central heating going into the sky, in the interim.

 

[jetsam]

I grew up in old houses designed to be 'heated' by open fireplaces. That's why I'm always puzzled when someone wants to build one on purpose.

 

[bholler]

I grew up in old houses designed to be 'heated' by open fireplaces. That's why I'm always puzzled when someone wants to build one on purpose.

Yes i am alway amused when people comment that houses were heated with open fireplaces for hundreds of years. Yes they burnt fireplaces but the houses werent exactly warm.

 

[Happy Stacker]

History of the chimney...https://www.apartmenttherapy.com/quick-history-chimneys-162580
"After the Great Fire of London in 1666, new building regulations demanded narrower chimneys, and professional chimney cleaners started hiring young boys, some as young as four, to shimmy up chimneys and clean out the soot."

 

[jetsam]

Yes i am alway amused when people comment that houses were heated with open fireplaces for hundreds of years. Yes they burnt fireplaces but the houses werent exactly warm.

My grandparents on both sides built their own farmhouses. My mother's parents used local stone, and my father's parents used hand-sawn timber (I still have 2 of the crosscut saws in a garage 2500 miles away). The stone house was more of a windbreak than a house until they added studs and insulation inside, and blocked off the fireplace. The wood framed house had an open fireplace but also a wood stove from the start, so it was pretty cozy when the fireplace damper was shut. Not so good upstairs when the fireplace was burning! I also lived in an 1800s house that seemed like it was designed around two huge masonary fireplaces, which were the only heat source. You could walk into one of them. Despite being a framed and insulated structure, the main reason you felt warm was that you were getting lots of exercise hauling wood in 24 hours a day.

I do really like open fires still (to an extent that puzzles my wife)... but I like 'em outside, because I also like being warm when I'm inside.​