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Fill chimney with insulation?

ecological_culture | Posted in General Questions on
I will seal it at the top and bottom, but that leaves 2 storeys of exterior wall of brick then cavity then brick then inside – no insulation. 
My chimney does not have an insert / metal flue, just brick.
I calculate it will take 0.3 bags of fiberglass @ $78/bag or 1.16 bags of cellulose @ $16/bag to fill the chimney.  I may be guilty of overthinking, but I made a spreadsheet (which you can comment on or copy): docs.google.com/spreadsheets/d/1e9ayMjp8AbrRi0rHl6iTtHVTQRs7xWSCvIju47uJIHU/
I would need to get the insulation chopper/blower onto the roof (easy enough from my balcony to the addition roof and from there to the lower-slope part of my barn-style roof), and do the work on a day with no wind.
Would there be mold risk?
(The chimney is 100 years old, but the mortar is in excellent condition, even though I know it has had no work in at least 33 years.)
Toronto

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Replies

  1. DCContrarian | | #1

    What's more important is to make sure it's air sealed and vapor sealed. Brick has a very low r-value -- 0.2 per inch -- so filling the core with insulation doesn't appreciably change the insulation value of the whole assembly, the brick provides a heat path around the insulation.

    1. ecological_culture | | #2

      Thanks.
      I'm imagining I could dangle a hose from the top of the chimney and spray silicone or something in all directions as I gradually pull up the hose. Any idea if that product/service exists? Would that help? The brick would still provide a heat path around the insulation. I love the look of my 100-year-old bricks - gorgeous colors, I say, but the chimney is at a rarely-seen part of the house. Should I spray the exterior of the chimney with something?

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