Should a Chimney Be HIGHER Than the Roof Peak?

[gtilflm]

Hi. We're planning out a wood stove install. Some details...

• Corner install
• 4/12 roof pitch
• From peak to chimney exit/enter point of roof, it's about 20.5 ft. horizontally and about 21.5 ft. along the roof/shingles

A bit of trigonometry tells me that we'd need about 7 ft. of chimney from the roof to get to a height that is just above the peak. Just minding the 3-2-10 rule, we'd need about 5.5 ft.

My Question: Recently, we were advised that it's best to have the chimney be above the peak for improved draft, etc. Given the cost of class A chimney pipe, is it worth the extra 1.5 ft. in order to be above the peak?

 

[begreen]

Is this a straight-up flue system with no 90º turns? What stove is going in and what will be the total flue height from stove top to chimney cap?
If this is straight flue of at least 13' then a Canadian stove like a Drolet, Regency, or PE, then I would try it out at the 5.5' above the roof as long as that meets the 10-3-2 requirement. Add more chimney if the draft is too weak. Regardless, the chimney will need to be braced at 5' above the roof exit.

 

[gtilflm]

It would be a straight run. About 9-10 ft. will be from stove to ceiling (there could be a couple 45's to make an offset to miss a truss), then about 2.5 ft. going through the "attic" (scissor trusses, actually), then a min. of about 5.5 ft. to meet the 10-3-2 rule.

As for the stove, we're working on that. Will likely be a Lopi. Does this setup sound like it would be more or less conducive to a certain type of stove?

 

[begreen]

If you have 15' of flue it should be ok. Worth a try.

 

[ABMax24]

Another factor is smoke smell, the higher up you get the top of the chimney the less the smoke will swirl down to the ground.

My chimney cap is almost 3ft above the roof peak, could be considered a lightning rod too, but it's high enough that for the most part the smoke stays up and drifts away, it doesn't easily get sucked into the negative pressure area on the downwind side of the house like a lower chimney would.

 

[gtilflm]

If you have 15' of flue it should be ok. Worth a try.

When you say "it" should be ok, what were you referring to?

 

[begreen]

The 15' high flue system and consequently, the Lopi that is connected to it. For the Lopi, 15' will be the minimum recommended flue height. There will be other factors that may affect this. Some of them are the tightness of the house, outside temperature, the 45º offset, prevailing winds, local terrain, etc. Take it up to 17' if you want to ensure better operation in milder 50º weather. Add an OAK if the house is tightly sealed or a manufactured home.

 

[gtilflm]

"OAK"??? Outside air intake, perhaps?

The house (not mobile home) is new construction as of 2020 and we had a great blower door test result. So, the house is pretty tight. We're near Spokane, WA (if that matters) and there isn't any "local terrain" like a hillside or something (but we do have a number of tall Ponderosa Pines on the property).

As it stands right now, the total flue length will be about 17-18 ft.: 9-10 ft. inside + 2.5 ft. through trusses + 5.5 ft. above the roof.

 

[begreen]

Yes, OAK = outside air kit. It sounds like the stove will need one. I think they are required for new construction in WA state, but don't quote me on it.

As it stands right now, the total flue length will be about 17-18 ft.: 9-10 ft. inside + 2.5 ft. through trusses + 5.5 ft. above the roof.

That should work well for most any stove.