Silicone Roof Flashing for Pellet Vent?

tbear853

Burning Hunk
Anyone here use one of those red silicone roof boots on a metal roof to seal to a pellet stove flue pipe ..... and if so, how's that standing up to pellet stove vent temps?

Currently, as it has been for years, my pellet stove's 3" flue comes out the back of the stove and makes a 45degree turn and then goes 36" out through the wall thimbles (alongside the 2" outside air inlet pipe) into a tee secured to a bracket I made on the wall of my carport (exterior side), the verticle pipe goes straight up a total of 15 feet to a pellet vent cap that terminates about 4 feet above the edge of the 8/12 pitch main roof. There is a bracket there at the edge of the roof too.

Due to some serious wind and the fact that I put my roof on in 1991, it being a three tab shingle roof ... I lost some tabs recently and upon reflection, I realized it's time for a roof. The house is a log home, we've wanted a metal roof for years, so very soon the roofers will be here to roof it in metal.

Question is, where that flue pipe goes straight up the outside wall of my carport it goes through the roof of my carport near the eave end .... up through the overhang. I have already purchased new pellet vent and tee as my current one is "old" and the outside galvanized part is "rusty" in places.

I am thinking either use a red silicone high temp flexible boot around the flue to seal to the new green metal roof .....
..... or maybe throw in a couple 45 degree joints to create a sort of dog leg to run the vent up past the carport roof without a hole.
 

mralias

Minister of Fire
Apr 29, 2008
1,100
MA
Anyone here use one of those red silicone roof boots on a metal roof to seal to a pellet stove flue pipe ..... and if so, how's that standing up to pellet stove vent temps?

Currently, as it has been for years, my pellet stove's 3" flue comes out the back of the stove and makes a 45degree turn and then goes 36" out through the wall thimbles (alongside the 2" outside air inlet pipe) into a tee secured to a bracket I made on the wall of my carport (exterior side), the verticle pipe goes straight up a total of 15 feet to a pellet vent cap that terminates about 4 feet above the edge of the 8/12 pitch main roof. There is a bracket there at the edge of the roof too.

Due to some serious wind and the fact that I put my roof on in 1991, it being a three tab shingle roof ... I lost some tabs recently and upon reflection, I realized it's time for a roof. The house is a log home, we've wanted a metal roof for years, so very soon the roofers will be here to roof it in metal.

Question is, where that flue pipe goes straight up the outside wall of my carport it goes through the roof of my carport near the eave end .... up through the overhang. I have already purchased new pellet vent and tee as my current one is "old" and the outside galvanized part is "rusty" in places.

I am thinking either use a red silicone high temp flexible boot around the flue to seal to the new green metal roof .....
..... or maybe throw in a couple 45 degree joints to create a sort of dog leg to run the vent up past the carport roof without a hole.
Not too sure about what flashing you should use but I hope you bought 4" venting as your Elevation Level (EVL) based on the above description is well over 17. I'm surprised it has worked all these years with the 3".
 

tbear853

Burning Hunk
Thank You for the reply. :)

I only have 15 feet verticle .... but I guess that 17 factors in the tee and 3 feet horizontal. I looked all through my install manual, it does say use 4" when running the ss liner more than 15 feet up an existing chimney ... but shows no limits when venting through a side wall into a tee and then verticle except to say a verticle of 5 feet or more is best if in an area subject to power outages.

Anyway .... mine has been working great for a really long time. What I bought new is the same 3" ID Dura Vent .... but I am considering a different venting route once outside the house. If I do the two 45 degree angle dog leg to bypass the eave of the carport roof, it'll move the vent cap further down the roof line on the gable towards then front porch and then I'd eliminate one 3 foot section of vent and still be over 2 feet above the roof gable end.
 

railfanron

Feeling the Heat
Nov 2, 2013
447
Perry MI
If it's going up through the roof that is going to be replaced the roofers will know exactly how to do it properly.
Ron
 
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bags

Minister of Fire
Oct 12, 2014
2,372
Kentucky
The roof pipe flashing boot will be fine if done right. They have some that are designed for chimney and vent pipes. You may need to go around a metal one with the rubber / silicone one. I've done plenty. Your pellet vent pipe will not be very hot that far up anyway. Not like a 2 foot sidewall direct vent. The metal roofing manufacturers make roof flashing boots specifically for chimney apps.

You will not be the only one with a metal roof with a chimney vented thru. There are different boots for different apps. If you have a reputable roofing co. doing the job they will do the correct thing as mentioned. For peace of mind ask them what they intend to do or use.

I know the red handles B-vent but ideally a pellet vent will have a metal cone deal with a flashing collar and then possibly the rubber roof boot if that helps.

Then again it is always nice to avoid as many roof penetrations as possible so plan B might be the way to go but if you can not or do not want that then anything can be dealt with. It never hurts to question the roofer and get their input but do that in advance. They should be able to show and explain what is what and walk you thru it. If not........ Ya might want to find another.
 

Tails1

Feeling the Heat
Nov 19, 2016
281
Ajax, Ontario Canada
I wouldn't consider plan B as adding more 45 joints is going to raise your EVL even higher and make cleaning harder too. What are you using now for a boot?
 
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tbear853

Burning Hunk
Good points all!

I wouldn't consider plan B as adding more 45 joints is going to raise your EVL even higher and make cleaning harder too. What are you using now for a boot?
I used a galvanized metal boot when I installed the pipe, but I knew that roof wasn't going to last but so long. I had thought a lot about bypassing the carport roof's eave end, the piercing is only about 18 inches from eave edge and anything that get's past the boot and runs down is just gonna run down the outside wall anyway.

Maybe I'm overthinking it? :D

I may just use another new galvanized boot and let it match the pellet vent .... or paint it black if I paint the pellet vent.

The new metal roof will have raised stiffenings pressed in place and so will not weave in with the boot base like it would with shingles. The silicone high heat boot (I was told that no hotter than pellet vent got out there, even the dark EPDM rubber boots would survive .... and experience tells me that's likely the case unlike a single wall flue or wood stove flue) is a flex boot that will attach with multiple screws and sealant to even corrugated metal.

http://www.pipebootexpress.com/?utm_source=bing&utm_medium=cpc&utm_campaign=*Search: Pipe Boot Express - JF&utm_term=roof vent pipe boot repair&utm_content=Pipe Boot: Roof - Vent

;)
 
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bags

Minister of Fire
Oct 12, 2014
2,372
Kentucky
Yes the boots for pipe roof penetrations are pliable and contour to the ribs in the metal panels. There is a metal ring that bends easily that gets screwed thru.
 
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gfreek

Minister of Fire
Not sure if this will apply to you and how much snow and ice you get but being a metal roof, I'd use a bracket to hold the pipe upright and maybe some snow/ice guards to prevent the pipe from shearing off. I've had my plastic plumbing vent sheared off from snow/ice..
 
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tbear853

Burning Hunk
Not sure if this will apply to you and how much snow and ice you get but being a metal roof, I'd use a bracket to hold the pipe upright and maybe some snow/ice guards to prevent the pipe from shearing off. I've had my plastic plumbing vent sheared off from snow/ice..
Normally, not a lot .... but occasionally, we have had serious snow .... so I have already been thinking of braces for the 2" and 3" plastic vent pipes. The stove pipe or "pellet vent" has a brace at the adjacent roof edge that is very secure.
 

Highbeam

Minister of Fire
Dec 28, 2006
16,098
Mt. Rainier Foothills, WA
I thought one of the benefits of forced exhaust was avoiding this situation. Why don't you just put a 90 on it under the soffit (instead of the 45) and blow it out sideways to avoid the roof penetration entirely. I hate roof penetrations, they leak, add labor to the job, add parts to the job.
 
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tbear853

Burning Hunk
I thought one of the benefits of forced exhaust was avoiding this situation. Why don't you just put a 90 on it under the soffit (instead of the 45) and blow it out sideways to avoid the roof penetration entirely.
Well, the point of having good rise was to maintain a good natural up draft in case of sudden power outages ... which we occasionally have. My 15 foot verticle seems "long" but it's always worked well. Where my pipe exits the wall under the eave of the carport roof allows me just a bit over 5 feet from tee to where I'd have to put a 90 to miss the eave edge.

I was out there looking a while ago, measuring, still thinking. I have 69" from top of tee to lower edge of soffit. I can run it 5 feet up from tee and put a 90 in and a horizontal exhaust cap or spout (one not inviting to nesting birds) .... might do that.

Then the extra pieces of 3" Dura Vent I bought on sale ..... guess I could run them on craigs list / etc if I do shorten it. :D
 
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tbear853

Burning Hunk
Roof is on, ran roofing metal it over hole after removing old flue & flashing .... after 26 years it was about rusted through the outer galvanized layer, the inner SS is shiney though. I used a sawzall to whack it into short pieces as the joints even rusted together in places and some of the liner that was cut below swaged end fell out. Kept a couple pieces ... I can maybe someday need a small piece of SS. I also found that inside was totally clear of soot build up .... so that new yard vac / blower I used a few months ago WORKED.
Anyway .... took 4 pieces of the new flue I had bought back to TS & they happily refunded that $110 (3 foot sections, had got on a 25% manager's special a few months ago) and kept the new tee with cleanout cap and two 3 foot pieces. Gonna get a 2 footer and 90 and exit piece before next winter, will end up with 3 foot horizontal, tee, 5 feet up, a 90 degree turn ... and an exit under eave.
 
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