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Sealing duct-work

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I just read the third edition of "Rocket Mass Heaters" and I noticed something a little contradictory regarding the stoves intestines...or duct-work...or whatever you want to call it. There is a case study of a mass heater that utilizes adobe brick for it's duct-work. BUT, in another section of the book regarding duct-work it's said that you should tape all the joints in your duct-work so it doesn't leak nasty gasses. The adobe duct-work isn't taped...it's probably not totally air-tight. SO, why would I need to tape my metal duct-work if I am covering it in cob?
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Location: Northern New York Zone4-5 the OUTER 'RONDACs percip 36''
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Anthony Troia : Counter-intuitively even with the best of careful hands-on craftsmanship, sealing up Adobe bricks or the Rock and Cob Lasagna that a good Thermal Mass

is made from is much easier than getting a perfect bonding of the stovepipes slick surface to the rest of the Cob/Thermal Mass. The idea is to do a trail build outdoors,

Generally thesis a two step process with a final vertical chimney put in place immediately after you place the drum over the heat riser, this separates the Rocket burner
base from the Thermal Mass and makes sure that the first part works before moving onto the second part, laying out the Stovepipe to check that it will go into the space
you have planned for it !

Often after you have it perfect outside, moving it to the inside gets to be a time-consuming and finicky last little bit, it is a good idea to plan For the extra time this last job
takes. That way there will be less temptation to slap it together, and just get on with the build! The Care you give this part of the job will keep you from the temptation
later when you are tired to cut corners, The end goal is to have a hand-crafted Family Heirloom piece of built-in furniture to show off with pride when you have visitors !

For the Good of the Crafts ! Big AL
Anthony Troia
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Cool, thanks.
Do have a suggestion for heat resistant duct tape? What brand/model of tape do you use?
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Location: Upstate NY, zone 5
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There is an aluminum foil tape made for sealing heating ducts which is made from a (usually shiny) thick foil with adhesive on one face. You should be able to find it at hardware stores.
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