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  1. #1
    Join Date
    Jan 2014
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    6

    Proper way to insulate around fireplace

    I tore out the drywall around our wood fireplace to redo the basement. I noticed there is a strong cold draft coming through the insulation that is tucked between the bricks and the studs. The fiberglass is also black in spots where it's been "filtering" air infiltration.

    If I pull the insulation back I see about a < 6 inch air gap to the brick that surrounds the chimney pipe (I assume).

    I know the first problem is sealing from the outside must not be adequate if that much air is coming through, but the second question is how do I insulate this properly from the inside?

    Some of the gaps are very large. Fiberglass insulation does not seem like the appropriate material here. Above that the MIRA-BILT aluminum insulation board is the only thing between the air gap and the drywall.








  2. #2
    Join Date
    Aug 2004
    Location
    S.E. Pa
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    6,137
    I always enjoy seeing crime scene photos esp. before the fire.

    uh, you must maintain a 2" clearance to combustibles, which means an air space. You cannot pack insulation in, on or tightly around a masonry fireplace like that. Seal and insulate the outside wall where it abuts the chimney. You are allowed to have sheathing touch the chimney but not framing and you cannot pack the space with insulation. . Properly built, there is no need for insulation over the header. Just insulate (weatherize) the walls adjacent.

  3. #3
    Join Date
    Jan 2014
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    6
    Quote Originally Posted by hearthman View Post
    I always enjoy seeing crime scene photos esp. before the fire.

    uh, you must maintain a 2" clearance to combustibles, which means an air space. You cannot pack insulation in, on or tightly around a masonry fireplace like that. Seal and insulate the outside wall where it abuts the chimney. You are allowed to have sheathing touch the chimney but not framing and you cannot pack the space with insulation. . Properly built, there is no need for insulation over the header. Just insulate (weatherize) the walls adjacent.
    Thanks, that's sort of what I figured. The previous owner did lots of "not supposed to", I found one electrical connection he did wrapped with duct tape. The house has been one big fire hazard.

    Help me make sense of what I'm seeing, the pictures don't show depth nicely. I have the red brick for the fireplace, directly behind and touching it is one layer of off-white brick where the insulation is, then behind that with a >2" (more like 6") air gap is another set off off-white brick you see in pic#3, which I assume is the brick around the chimney.

    When you say sheathing can touch the chimney what do you mean? What would sheathing be? Would it help to pull some of that MIRA-BILT board off for better pictures? The MIRA-BILT board you see has at least a 2" gap to the off-white chimney brick behind it, probably more like 6-8".

    Should normal drywall go here or is a cement board better? I'd rather hire a professional for this portion, but what do I look for? Fireplace installer?

    I also need to make sealing the outside a priority, there is a massive draft coming through this airspace somehow. As a quick look I can't see where it's coming from outside.

    Here's a somewhat better picture showing what I believe to be the real chimney packed about 8 inches back.


  4. #4
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    Aug 2004
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    S.E. Pa
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    You've got so many voids and caves in there I wouldn't touch it until you've had a Level II inspection by a hearth pro and corrected all the problems. Too big of a mess to deal with online. The sheathing means simply the outside wall sheathing can touch and the inside drywall, paneling can touch but the framing must be relieved by a 2" gap. All those gaps and sloppy brick work scream disaster. What else did this mason do? Hire a pro

  5. #5
    Join Date
    Jan 2014
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    6
    Quote Originally Posted by hearthman View Post
    You've got so many voids and caves in there I wouldn't touch it until you've had a Level II inspection by a hearth pro and corrected all the problems. Too big of a mess to deal with online. The sheathing means simply the outside wall sheathing can touch and the inside drywall, paneling can touch but the framing must be relieved by a 2" gap. All those gaps and sloppy brick work scream disaster. What else did this mason do? Hire a pro
    I called around today to hearth pros and fireplace installers and was told I needed to call a chimney sweep. So I have one scheduled for Thursday.

  6. #6
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    Jan 2014
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    6
    Thanks for all of the info. My pictures must not have reflected the situation very well. I had a pro come out today and he told me nothing to be concerned about after inspecting everything.

    He said I have the chimney, which are enclosed in cinder blocks, a 4" air gap and 4 layers of brick to where the insulation was. He said if it were him he'd just seal the gaps with sand mix cement or mortar or whatever. He said it looks like they just used all of the leftover bricks from construction around the fireplace.

    The cold air is because the caulk between the fireplace brick and siding on the exterior has degraded.

    He told me if I didn't believe him I could start a big fire in the fireplace and see that there is no change in temperature at those bricks. I did that and he's right. The thing I didn't like was he jokingly said it would help him sleep better at night too if I did that experiment. I sit here still wondering if he was joking or if he didn't know what he was doing and it was all conjecture.

  7. #7
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    Aug 2004
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    S.E. Pa
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    All I read was 'opinion', which unfortunately, so many chimney sweeps are full of. In their arrogance, they scoff at codes and laws. What he rendered was an engineering opinion. Ask him for his credentials but especially a copy of his seal as a registered licensed professional engineer in your state.

  8. #8
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    Jan 2014
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    Quote Originally Posted by hearthman View Post
    All I read was 'opinion', which unfortunately, so many chimney sweeps are full of. In their arrogance, they scoff at codes and laws. What he rendered was an engineering opinion. Ask him for his credentials but especially a copy of his seal as a registered licensed professional engineer in your state.
    That's kind of my thoughts too, but don't know where to go from here. All of the hearth specialists I called simply referred me to chimney sweeps.

  9. #9
    Join Date
    Jan 2014
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    6
    Is there any way to use your industry info to find me someone to talk to in Denver, CO?

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