Easy chimney height question

[Highbeam]

Folks, I am laying out the installation of the Hearthstone Heritage and the manual calls for a 13-30 foot tall chimney. I am going to be on the low end with a 7.5' ceiling height in the stove room, 3 feet of attic, and 5 feet above the roof since I don't want to brace it. So I've got 15.5 feet of completely straight chimney minus however tall the stove is. The million dollar question.... where does the "chimney" begin? Is it measured from the firebox floor or the actual beginning of pipe?

I will use double wall pipe in the room and zero bends so draft will be ideal for the given length of pipe but I will be at the bottom of HS's range. It seems that the HS stoves are relatively draft sensitive.

I wanted to use a slightly elevated hearth, with a 2x4 on edge at the base of the stack. Then plywood, micore, durock, and stone. This elevated hearth might burn up 6" that I don't have to spare so the reference point of the measurement becomes important.

 

[jtp10181]

I assume with the pitch of your roof the 5ft meets the 2/10 rule?

 

[BrotherBart]

It doesn't sound like you have any other option than to burn the stove and see how it goes. If the draft is crap then add a section of pipe and address the bracing issue.

 

[Highbeam]

Whoops, I must have been unclear.

My question is how do you measure the chimney height? Between which two points? Top of cap to firebox floor? Bottom of connector pipe to top of chimney pipe?

I am within a foot of Hearthstone's requirements and this little detail is a big deal. Not clear with a graphic or from wording in the manual. Thanks for your input.

Yes, low slope roof and 5' easily meets the 2-10-3 rule.

 

[BrotherBart]

The only reference to that I have ever seen is in the Pacific Energy stove manuals. They say measure from the bottom of the firebox/stove.

 

[jtp10181]

I would always assume to measure from where the chimney starts... the fireplace itself is not the chimney, it is the firebox. I don't know why it would be included in the "chimney" height.

 

[Gooserider]

As a FWIW department, my VC Encore (non-cat) manual says the height should be measured "from the flue collar to the top of the chimney" Different brand, but same basic idea of the reversible (rear or top vent) flue collar.

The definition is still a bit vague in that it doesn't say WHERE on the flue collar, but I would guess the center in a rear-vent configuration, and the top of the stove in a top-vent configuration.

Gooserider

 

[mayhem]

I would play it safe and assume the chimney begins at the flue collar...right where it goes through the outer layer of the stove itself. Doesn't seem sensible to me to include the firebox since that the combustion chamber, not the exhaust.

 

[webbie]

In a straight up job like this, the flue collar is a good place to measure from - I predict this chimney will draft to beat the band - straight up, interior, insulated (class A) chimneys are usually the best and will perform well even on the short end....in fact, probably better than a taller one of similar construction, which might have too much draft.

 

[Rhone]

I really doubt you'll have a problem. I could be mistaken, but I think the 13' they're referring to includes installs with mostly flexible chimney which restricts draft, you're using rigid which doesn't. Having a straight run of rigid chimney inside, insulatated with no corners/curves you should be drafting like crazy. I wouldn't give it one worry.

 

[stoveguy2esw]

the 13 foot vertical is likely taking into consideration worst case, exterior, elbows, etc. 15.5 minus the stove will likely put you just short of that, but i think you will be ok as long as the 10-3-2 rule is covered once through the roof itself. the flue must have 3 ft exposed above the roof penetration minimum , which you meet , it must also have at least 2 ft. clearance above any part of the roof withing 10 ft of the flue itself.not counting the cap. essentially imagine this , you are on your roof with a 10 ft. board, a level, a tape measure, and a marker with you. to check the 10-2 rule (we know you have 5 ft exposed) imagine taking the board and laying it on the roof , uphill from the chimney so that one end is butted against the flue and the other is resting on the peak or on the roof uphill from the flue. now , lay the level on the board and raise the end that is against the flue up the side of the pipe until the bubble levels out , mark the flue there. then simply measure from the mark up the side of the flue to the top. this measurement must be at least 2 ft. if you have that configuration then you are good as far as the flue is concerned. any draw issue with that setup is not related directly to the flue, if draw is not present, then you are looking at other issues such as negative pressure (install an OAK kit), or possibly a higher building or rooftop in close proximity that is creating down currents decending on your flue. in some instances being in a steep valley or in a heavily forested area with tall trees wrapped closely around the house, can create down currents as well and may be difficult to deal with.

sorry for being so long winded , i kinda got on a roll there, but i explain this very thing this way to people a lot in my profession and it always seemed the easiest to understand, i hope this is helpful to you

EDIT unless otherwise specified , measure flue height from the collar, sorry i missed the boat on the question too lol.

 

[Highbeam]

Thanks folks, I think I'll go ahead with my raised hearth and then just stay less than 5 feet above the roof. The only way this install would be more ideal is if it were right on the ridge of the home. The existing lined masonry chimney which is fed by the big Lopi which sits on at least a 12" raised hearth seems to draft very well on a chimney which extends 15 bricks (on the low side) above the roof. My guess is 3-4 feet above the roof.

I'm getting bids right now for chimney tear down. One guy was 1500 and that is too much so another one will be here tomorrow. I know it is not rocket science but it is a lot of time that I could better spend planting pupmkins. I measured 9 -1/8 cords of firewood all split and stacked last night.

So from the collar. That should have been easy to mention in the owner's manual. Fortunately sites like this exist to save the day.

Thanks again.

 

[begreen]

I'm getting bids right now for chimney tear down. One guy was 1500 and that is too much so another one will be here tomorrow. I know it is not rocket science but it is a lot of time that I could better spend planting pupmkins. I measured 9 -1/8 cords of firewood all split and stacked last night.

How old is the chimney? Is it lined? Our fireplace + chimney was old and unlined. It took 3 of us 3 days to completely remove it. Taking it down was actually one of the easier parts. Containing the mess and hauling away all the old mortar, dust and debris and the bricks was the more time consuming part.

 

[Highbeam]

The fireplace and chimney were built in 1963, no seperation to framing members and the back is cracked out. It has a clay liner and the SS liner. Mostly, we just need the space and want a freestanding stove that works silently. The folks doing the bidding seem to think it is a deal where they show up in the morning and before I am home from work the whole thing is gone. The two bidders use dump trailers. If taking it down is the easy part then I am no stranger to taking debris to the dump. I always thought I could do it if I had the time to spend. Unless I get a bid below 1000$ I'll be doing it this summer.