Interior Chimney Chase Install - sorry its a longer post

[Wxtrendsguy]

Building a new house this summer and want to make sure I know what I am talking about in case I need to intervene if the installer puts in the chimney the wrong way or tries to add a short cut. Sorry to doubt the many great installers on this site but the industry is full of poorly trained people and building inspectors in my opinion are not much better.

Some sort of EPA Phase II certified fireplace will be install along an interior wall in the great room with 18' ceiling. A Selkirk or like product insulated class A chimney will be used as well. The ceiling will be framed using scissor trusses but the insulation will be open cell spray foam on the underside of the roof creating whats called a hot roof. The flue pipe will be enclosed in a chase up to the ceiling. So now this is where it gets interesting. What is the best way to go through the ceiling and then out the roof trying to maintain a very tight building shell around any penetration leading to the outside?

I was thinking about putting a ceiling into the chase at the same height as the rest of the great room and then continuing the chase all the way up and out through the roof. The interior walls of the chase from the ceiling to the roof would be sheet rocked inside the chase and spray foamed from the attic side maintaining the sealed envelope and then use a product like an Attic Insulation Shield from Selkirk to make the penetration through the ceiling in the chase and use SUSI shielding insulation to help make it as airtight as possible and then insulate with bats the top of the ceiling inside the chase being careful to not be any deeper than the attic shield allows. The rest of the install above that is like a typical chase top.

Overkill?

 

[DAKSY]

Building a new house this summer and want to make sure I know what I am talking about in case I need to intervene if the installer puts in the chimney the wrong way or tries to add a short cut. Sorry to doubt the many great installers on this site but the industry is full of poorly trained people and building inspectors in my opinion are not much better.

Some sort of EPA Phase II certified fireplace will be install along an interior wall in the great room with 18' ceiling. A Selkirk or like product insulated class A chimney will be used as well. The ceiling will be framed using scissor trusses but the insulation will be open cell spray foam on the underside of the roof creating whats called a hot roof. The flue pipe will be enclosed in a chase up to the ceiling. So now this is where it gets interesting. What is the best way to go through the ceiling and then out the roof trying to maintain a very tight building shell around any penetration leading to the outside?

I was thinking about putting a ceiling into the chase at the same height as the rest of the great room and then continuing the chase all the way up and out through the roof. The interior walls of the chase from the ceiling to the roof would be sheet rocked inside the chase and spray foamed from the attic side maintaining the sealed envelope and then use a product like an Attic Insulation Shield from Selkirk to make the penetration through the ceiling in the chase and use SUSI shielding insulation to help make it as airtight as possible and then insulate with bats the top of the ceiling inside the chase being careful to not be any deeper than the attic shield allows. The rest of the install above that is like a typical chase top.

Overkill?

Not overkill, per se, but you'd be better off choosing your unit so we know what venting configuration you'll have. "Some sort of EPA Phase II" doesn't help much, as all manufacturers require different installs. As far as "Selkirk or ...Class A" goes, you will find that some of the EPA rated units don't use EITHER. Again, each manufacturer has different specs & guidelines. If you can narrow your selections down to a few units & manufacturers, we can help you out.

 

[begreen]

In the great room chase, is a fire stop still required at the nominal 1st fl level?

Note that you don't want the pipe exit to be air tight. Most roof flashings are vented either with slots or dimples.

Agreed that you should do the research on the EPA fireplace so that you get the right one for the house. Do you want it to have a ducting option to deliver heat to another part of the house?

 

[Wxtrendsguy]

Lennox Villa Vista, Montecito Estate, BIS Tradition, possibly the new FPX 44 if its available though not sure it will use class a chimney.

Still might be convinced at the end of the day to do a masonry heater but the chase above to the roof would actually still be the same as if I used a ZC Fireplace...

 

[rideau]

You hav not said anything about how big your home is or whether you hope to heat the entire home with the fireplace.

Without going into specifics, I'd suggest installing the best chimney on the market, the one that is most apt to be usable if you change your mind down the road as to type of appliance you want to use, as many do. And I would probably make my fireplace opening quite large, with an incrporated non-combustible design that let me adjust the size of the front opening pretty easily, to give flexibility if I wanted to change my fireplace down the road. In other words, make your installation as flexible as possible. Also, design it so it is easy to get at the chimney to service , should you have to. And, space permitting, I'd probably put a nice big raised hearth in front of the fireplace, with a good R-rating, so if I ever wanted to switch to a wood burning stove, I could just slip any one I chose in place. Meanwhile, raises the fireplace to a nice viewing height, raises the heat a bit, and provides a place for seating, for wood, and fire maintenace tools. And, if not a raised hearth, at least a good size, good R value hearth.

 

[Wxtrendsguy]

Sorry Rideau for the lack of details. 2 story home, approx 2500 sq ft, 2 bedrooms upstairs, 1 master bedroom on first floor on east end of house, center section of the house is foyer and office in front with a great room behind that approximately 15'x 26' in size with 18 ft ceilings, entire back wall of great room faces south with windows for passive solar gain, right side of home is large country eat in kitchen with 9 ft ceilings. Upstairs will be a loft area that overlooks part of the great room and foyer with one bedroom over the office and the other over the master.

So basically its 3 boxes on the lower level with a side entry garage on the front. Front of house faces north and goal was to have minimal windows and door on that side.

Plan to heat the house using a Carrier Infinity 20 high efficiency heat pump and heat recovery ventilation as well. 2x6 exterior walls, open cell spray foamed the entire building envelop. ACH (air changes per hour) around 1/2.

 

[DickRussell]

Wx, if I understand your plan of the chase, you will have a chase in the "attic" (space between upper and lower chords of the scissor trusses), and running down to the floor of the great room. That suggests the potential of some transfer of roof load in winter down to the great room floor sysem, unless you design for it. There also could be some upward force due to "truss uplift," when seasonal changes in moisture content of the truss members can result in lifting the walls of the chase off the floor or lifting of the ceiling off the upper end of chase. Normally, when trusses are used the interior wall partitions would be fastened to the trusses with special clips (I forget the name), that allow for upward movement, and sheetrock on the ceiling is not fastened any closer than perhaps 16" from the wall. Clips are used to anchor the edge of the sheetrock to the top of the wall, allowing a bit of flex of the sheetrock to avoid opening a crack where ceiling meets wall.

In my house, I have an insulated chase running through the corner of a bedroom on the upper level. The woodstove is on the lower level, connected by double wall pipe to the section mounted at ceiling level where the insulated chimney starts. The chase is largely as you describe; it is framed, with sheetrock on the inside, insulated, and covered on the room side with more sheetrock, with all joints sealed against air leakage. I built it this way on the assumption that the woodstove would be in operation a smaller fraction of the time than it would not. With the chimney full of cold outside air most often, I treated the airspace within the chase as "outside."

 

[webby3650]

possibly the new FPX 44 if its available though not sure it will use class a chimney.

It does use class A chimney.

 

[Wxtrendsguy]

Wx, if I understand your plan of the chase, you will have a chase in the "attic" (space between upper and lower chords of the scissor trusses), and running down to the floor of the great room. That suggests the potential of some transfer of roof load in winter down to the great room floor sysem, unless you design for it. There also could be some upward force due to "truss uplift," when seasonal changes in moisture content of the truss members can result in lifting the walls of the chase off the floor or lifting of the ceiling off the upper end of chase. Normally, when trusses are used the interior wall partitions would be fastened to the trusses with special clips (I forget the name), that allow for upward movement, and sheetrock on the ceiling is not fastened any closer than perhaps 16" from the wall. Clips are used to anchor the edge of the sheetrock to the top of the wall, allowing a bit of flex of the sheetrock to avoid opening a crack where ceiling meets wall.

In my house, I have an insulated chase running through the corner of a bedroom on the upper level. The woodstove is on the lower level, connected by double wall pipe to the section mounted at ceiling level where the insulated chimney starts. The chase is largely as you describe; it is framed, with sheetrock on the inside, insulated, and covered on the room side with more sheetrock, with all joints sealed against air leakage. I built it this way on the assumption that the woodstove would be in operation a smaller fraction of the time than it would not. With the chimney full of cold outside air most often, I treated the airspace within the chase as "outside."

Dick,

You are basically right on in understanding the concept. The insulated chase will only be between the upper and lower chords of the trusses. Below the lower chord down to the great room floor it will be an uninsulated chase and part of the interior of the house in conditioned space.
I guess you could almost envision an upside down skylight.

 

[Dave A.]

I thought the big benefit of using a stove vs. an insert is capturing the heat from the stove pipe in the living space. So I don't understand why you would want to cover it up inside a chase.

(In fact, I've been wondering why with an insert you'd even want to use a block off plate at the damper -- am thinking it might be better to put the block off further up in the chimney, leave the surround off -- or have a ventilated surround -- and use a small fan to get more of the heat from the liner and insert out of the sealed in fireplace and into the living space).

 

[webby3650]

I thought the big benefit of using a stove vs. an insert is capturing the heat from the stove pipe in the living space

Thats not the case at all. The big benefit is having all the radiant heat from the woodstove in the room, not having it stuck back in a fireplace. Compared to the stove, very little heat is gained from the stovepipe.

 

[Wxtrendsguy]

I thought the big benefit of using a stove vs. an insert is capturing the heat from the stove pipe in the living space. So I don't understand why you would want to cover it up inside a chase.

(In fact, I've been wondering why with an insert you'd even want to use a block off plate at the damper -- am thinking it might be better to put the block off further up in the chimney, leave the surround off -- or have a ventilated surround -- and use a small fan to get more of the heat from the liner and insert out of the sealed in fireplace and into the living space).

As i understand it...Since the vast majority of the pipe is in conditioned space (ie inside the building envelop) it will add BTUs to the house whether it is inside a uninsulated chase or not. The other purpose of an insulated class A chimney is that the flue gases stay hot all the way up and out which helps to prevent creosote buildup and also improves draft.

 

[Dave A.]

Sure with insulated (class a) pipe running through the chase in the room there wouldn't be much of any heat from the pipe anyway. Where you might pick up heat would be running single wall stove pipe through the living space -- when I mentioned about heat from the stove pipe, I was thinking single wall. Am learning about these things myself, so am not making recommendations but rather asking questions. And as you point out, if you were to run the single wall through the room, there would be some cooling of the flue temps -- whether or not that should be an issue, I'm curious myself.

 

[Wxtrendsguy]

Sure with insulated (class a) pipe running through the chase in the room there wouldn't be much of any heat from the pipe anyway. Where you might pick up heat would be running single wall stove pipe through the living space -- when I mentioned about heat from the stove pipe, I was thinking single wall. Am learning about these things myself, so am not making recommendations but rather asking questions. And as you point out, if you were to run the single wall through the room, there would be some cooling of the flue temps -- whether or not that should be an issue, I'm curious myself.

Well you definitely do not want to run single wall pipe in a chase...I guess you could with proper clearances but that would be one big chase.
Flue temperature also plays a role in creosote buildup as the gasses condense on a cold uninsulted pipe. I see it now in my double wall steel air cooled chimney...plenty of creosote buildup in the upper half of the chimney...

 

[Dave A.]

Guess I didn't make myself clear. I meant single wall exposed open to the room (not in a chase). But somehow I got your message mixed up with another thread with a stove and see that you are installing a fireplace and not a stove -- so obviously in your case the class a and chase are appropriate, single wall would not be appropriate with a fireplace.

Nevermind

 

[Wxtrendsguy]

Guess I didn't make myself clear. I meant single wall exposed open to the room (not in a chase). But somehow I got your message mixed up with another thread with a stove and see that you are installing a fireplace and not a stove -- so obviously in your case the class a and chase are appropriate, single wall would not be appropriate with a fireplace.

Nevermind

Well when I was a kid I built a little log cabin fort in the Adirondacks and built a little brick fireplace with a couple of leftover stove pipes for a chimney. Built fires in there all the time and worked perfectly though it leaked a lot of smoke...but heck the walls leaked a lot of air so it didn't matter. Now almost 30 years later my kids have rebuilt the fort using the same wood and some new dead trees and that old stove pipe and fireplace are still there and working like the day I built it...too bad they don't make stove pipe like that anymore...