GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Dealing With a Chimney Below the Roof Line

1869farmhouse | Posted in General Questions on

I have an old fireplace in my living room with a big brick mantle.  The chimney was knocked in below the roof line when it was redone, but it still has 6 feet of brick in the ventilated attic.

In the winter, would the heat lost up the brick chimney be measurable if the chimney itself was well air sealed?  It’s tight and I verified with a fogger.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    PETER G ENGLE PE | | #1

    Certainly the heat loss would be measureable. With the right equipment, anything is. When you look at the air sealing, it is important to seal both the inside of the chimney and the space between the chimney and framing. Once you've got good air sealing, there's lots less heat loss. But masonry is still a very poor insulator compared to insulation. The best treatment would be to break the chimney down to the attic floor, then seal and insulate over the top.

    1. 1869farmhouse | | #2

      This is really what I was wanting to do haha. I just needed one more person to agree so that I could be sure I wasn’t crazy. Dirty old bricks are coming down tomorrow.

  2. BCinVT | | #3

    Unless you are fond of the fireplace I would suggest taking the whole thing out. It would free up some space,and could even save you a bit on property taxes. I once had a decommissioned fireplace and discovered that the assessment of my property included a standard $2500 (10 years ago) for any fireplace. Assessors often do their work without access inside the house, and there is a good chance most don't check to see if there is a chimney to match.

    1. 1869farmhouse | | #4

      Is it different for a wood stove? This house has two fireplaces, one was converted to a wood stove and I figured I’d do the same bro this one.

  3. 1869farmhouse | | #5

    Well, I started tearing the chimney down today, got about halfway through and my wife texted me she took the baby to his room because dust was coming out the bottom.

    I didn’t even consider asbestos content for 100 year old brick... I had the insulation tested (rock wool)... but it sounds like brick can be as bad. Sigh... hopefully not as bad as some other forms.

    1. Expert Member
      NICK KEENAN | | #6

      According to the EPA, "Cinder blocks, mortar, brick, and cement foundation do not typically contain asbestos and would not normally be sampled.".

      Are you seeing lovely spring weather? Run an exhaust fan to create negative pressure in the attic and open a window on the first floor. Seal the fireplace with plastic and tape. Soot and silica dust are lung irritants, you want to keep them out of the house and wear an N95 mask.

      1. 1869farmhouse | | #7

        Thank you. My unfocused googling was leading me to believe that old mortar almost always contained asbestos - glad that’s not the case and appreciate the info! I’ve done the other things you mentioned also - and yes, the weather is lovely up here in the attic today!

        1. 1869farmhouse | | #8

          The chimney has been demo’d down to the floor of the attic and capped with 4” of XPS and a generous serving of loc-tite foam. I pushed the approximately 12” of blown rock wool over the top and called it a day.

          1. Expert Member
            MALCOLM TAYLOR | | #9

            Well done!

          2. Expert Member
            NICK KEENAN | | #10

            Good work. I imagine you're covered in soot. Go reward yourself with a bath!

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |