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Chimney & Fireplaces/Insulation and Drywalling a Chase.


I presented this question to James Ball and he doesn't have a answer so I'll give you a try Randy.

I'm remodeling my Majestic Fireplace to add a raised Hearth that was originally installed as new construction at floor level. I'm in the Chicagoland area so it can it quite cold. I always had cold air around the fireplace and want to correct this issue with this remodel. My Chase was not Insulated and had no outside air into the fireplace. I'm putting in a ceiling and insulating the Chase. I will drywall with 5/8". I'm adding outside Air intake and Glass Doors. My question is since this area of the chase will be sealed tightly. Even around the Flue Firestop.

Will that part of the Chase need outside air for the 3 wall Flue to vent properly?
My Air Intake will be dampered to shut went not in use. I was thinking that I might need to divert some of the intake air into this part of the chase.


ANSWER: Hello John, all Pre Fab fireplaces  must be installed to the manufactures install instructions (even your building department will tell you this) so you much install the Majestic model you have any thing else could void the UL listing and cause a fire.

---------- FOLLOW-UP ----------

I am Re-Installing to the Installation Instructions that came with the fireplace. Keeping air gaps as noted. The instructions even note the outside chase should be insulated in cold climates which the original builder did not do.

The reason I'm asking the question is now that the Insulation and Drywall is up in the Chase and knowing how air tight it will be once I close it with the interior wall.
There is no mention about adding an air vent for the Chase (Which would somewhat defeat the purpose) in the instructions so I was thinking I'm missing something.

I was just wonder how does the 3 wall flue get air flow in the openings at the top of the fireplace where the flue connects for the outer 2 flues? Does air come down the Outside flue and up the Middle flue?

I guess I'm curious of how it's suppose to work.

Concerning the Majestic factory built fireplace, I would need the specific model number to be more informed as to the requirements of the manufacture and specific clearances. The building codes have always directed installation requirements to the manufactures install manual as part of their document, meening the manufactures install manual is the code.

As far as how does the triple wall pipe get its air, that's is easier. The inner most pipe is connected to the fireplace unit. This pipe contains the dirty air, creosote, soot, carbon monoxide, etc... This same pipe radiats heat externally that is captured between itself and the second pipe. This heated air wants to rise exit the top as well. This second pipe stops short of the top of the fireplace by a couple of inches but the third pipe or exterior pipe is connected to the fireplace. So as the heat rises between one and two, a negligible pressure is created that draws cool outside air down between two and three. This cool air collects with the radiant warm air between one and two and exits the top.

When you mentioned installing glass doors and parts in general, they must be UL listed for your system or approved by the Authority Having Jurisdiction (AHJ). The termination is critical to being engineered or listed for this fireplace to avoid a fire hazard.

Hope this helps.

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Randy Brooks


Inspection of Masonry, Pre-cast Tilt-up, and Factory Built Fireplaces as well as Free Standing & Insert, Gas, and Wood Appliances. We also provide Hearth Fire Loss Investigations, Litigation Support, Consulting Services, Flue Sweeping, Installation and Repair. Additionally, I’ve been a chimney sweep for 23 years, service and install hearth appliances as well as being recognized by the Superior Court of California as an expert witness.


Brooks Chimney Sweeping Since 1989 Ojai, CA Owner / President

NCSG, MEMBER,(National Chimney Sweep Guild), Member since 1990, Board of Directors representing Region 6, (CA, NV, AZ, UT, OR, WA, ID, WY, MT, AK and HI,) 2004-2011, ethics committee chair, 2004-2005, executive committee member, Vice President, 2006-2008, President, 2008-2011. CSIA, BOD (Chimney Safety Institute of America,) Board of Directors, ethics committee chair, 2004-2005, executive committee member, Secretary, 2005-2006, Vice President, 2006-2008, President, 2008-2011. HPBA, MEMBER, (Hearth, Patio, & BBQ Association,) since 2002. NFPA Member, (National Fire Protection Association) Since 2009. Technical Committee member for the 211 Standard.

California State Licensed Contractor, C61-D34, #750710. C.S.I.A., (Chimney Safety Institute of America,) Certified Chimney Sweep, #2580. Held since 1990 re-certified in ‘93, ‘96, ‘99, ‘02, ‘05, '08,'11,'14. F.I.R.E. (Fireplace Investigation, Research & Education Service,) Certified Inspector, #FP-006. Held since 2000, re-certified in ’03, ‘06, '09, '12, '15. Fireplace Investigation, Research & Education Service,) Advance Expert Consulting & Witness, certificate, ’05 N.F.I. (National Fireplace Institute,) Certified Gas & Wood-Burning Specialist, #133851. Held since 2002, re-certified in '05,‘08,'11,'14

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