Stove pipe and thimble design

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Kali's Revenge

New Member
Jan 24, 2023
Southern Chiba, Japan
Greetings from Southern Chiba, Japan.

I have some questions about stove pipes and designs. I apologize if this has been addressed before.

Briefly, we have decided to get a wood stove oven to provide auxiliary heating to our underfloor system for our self-built house. Electric bills have skyrocketed and we calculate that we can recover our expense in about 3 years.

We are inclined to hire a contractor to install the stove pipe. However, as I was an architect in the States, I am familiarizing with the design requirements to make sure that the contractor is doing a good job and understand the process.

What I have read and understand is that two 90 degree angles should be the maximum for a system. However, what I do not understand is that I see systems with a 90 degree elbow on the inside of the wall (vertical to horizontal) , a 90 degree on the outside wall with a clean out cap (horizontal to vertical) usually two offset elbows to clear the roof overhang.

I know that this may not be an ideal design. However, how does this square (no pun intended) with the two 90 degree angle suggestion?

Alternatively, I have seen designs, mostly from the U.K. that shows a 45 degree thimble to the outside and then a 135 degree clean out joint running upwards to the roof. This design would be more ideal as it stays within the two 90 degree turns.

Searching the Internet, I have yet to see a 45 degree thimble. Is this a custom design?

And finally, can thimbles be DIY? In other words, can one design a 45 degree functional thimble?

Thanks for any and all information that you may share.

The best practice is to go straight up thru the house and roof. That will provide the best performance and is often the least expensive route. The class A thimble and tee are expensive.

If installing an exterior chimney, use a pair of 45º stovepipe elbows on the interior to soften the interior 90º turn. Offsets a usually not allowed on an exterior chimney. Notch the roof overhang to avoid the offset there.

 stove venting 3 ways.png

A 45º thimble is an invitation for water intrusion during rain.
Just looking at this diagram. With our Cape option 1 could not be done. Not sure how option 2 would have worked since need a tight clearance to the rear wall ( Corner install) which is per PE 5” to corners (installer did 7”). Stove would stick out too far with the 45’s. Also need to clear the gutters on the rear full shed dormer so 2x 30’s were used to clear it. Our installer used ICC EXCEL. Like pic 3 double wall pipe about 36” total with slip section from the stove collar than a 90 to a wall class A thimble (EXCEL wall radiation shield used) to outside insulated tee with clean out. Top of stove to chimney cap 23’ add two feet to floor. All exterior work sealed before trim cover installed. Draft has been excellent and is best with temps under 40. Not sure what minimum flue height is was PE stoves.
It should work well. PE stoves generally are easy-breathering. The T5 will work ok on a 12' straight-up flue system at sea level.
Thanks begreen for your quick reply. Just saw in my manual 15’ minimum height. I actually was concerned by the angles but my installer said with the overall height it would draft well. He said in real cold weather I will have to shut the air down more which I learned on the negative temps we had awhile back. On a side note my wife’s loves your Alderlea and the color options. We liked the T4 but our dealer did not have any of these to look at.
Yes, 15' is the tested height from the base of the stove or about 12.5 ft. from the flue collar. I think you got the best stove. The T5 will afford more flexibility in loading and a longer burn time. It also has the swing-away trivet top which is great for cooking.
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Agree and the Vista has a max wood length of 18” vs 17” for T4 but the Alderlea aesthetically looks great. The T4 is also about a $1,000 more from what I see online.
The T4 should be about $500 less if the finish is the same. It's a smaller stove with a fixed top.
I meant $1,000 more than our Vista. I think around $3,300 for a T4.