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Community and Q&A

Brick house insulation

3rd Little Pig | Posted in GBA Pro Help on

Hello,

My situation: I have a brick house, that initially had plaster and lathe walls. With the floor joists supported by inner wythe, and the joist ends embedded in the brick. I removed the plaster and restudded the walls with 2x4s.

My concern: On the lower floor, I insulated the stud bays with batt insulation. I thought this was a good thing, however, after reading your article I think I may have been mistaken.  I am beginning work on the second story and don’t want to make matters worse.

My question: Is there a way to remedy this mistake? I noticed you mentioned EIFS/ synthetic stucco. I need to do something with the exterior, and that is something I have strongly considered.
  1) If this system is used, will that suffice as insulation for the second story?
  2) Could that also prevent freeze thaw issues, on the main floor with the batt insulation?

Thank you. Any information is greatly appreciated.

Tony

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Replies

  1. User avatar
    Dana Dorsett | | #1

    What is your climate zone/location, and how deep are the roof overhangs?

  2. User avatar GBA Editor
    Martin Holladay | | #2

    Tony,
    I'm assuming that you live in a cold climate (which is why you are concerned). That said, Dana's questions are good ones.

    Briefly: EIFS is a good solution. If you install an adequate thickness of exterior rigid foam, (a) you won't need additional interior insulation upstairs, and (b) your downstairs walls will be protected from freeze/thaw problems.

  3. 3rd Little Pig | | #3

    Thank you both for the quick response. It looks like I am in zone 6. About an hour north of New York City. My roof overhangs my walls by about 1 ft. Is that good/bad?

    Didn't think to ask before, but would vinyl siding accomplish this also with adequate exterior foam. I only ask because (while I really don'the like vinly siding) reading up on EIFS it sounds like finding someone that actually does it correctly may be tough. Just trying to figure my options.

    Thank you again for any help. Credible info is not easy to come by.

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Tony,
    I assume you've read this article: Insulating Old Brick Buildings.

    If you choose to install EIFS, the system will need to be installed by a certified EIFS contractor, for insurance reasons. A little online research and telephone research should put you in touch with a few EIFS contractors.

    The key element in the wall assembly -- the element you need to keep your bricks warm and safe -- is a layer of exterior rigid foam. Vinyl siding will neither help nor hurt. If you want to install vinyl siding, you can -- but it will only help if the vinyl siding system includes and adequately thick layer of exterior rigid foam.

  5. 3rd Little Pig | | #5

    Martin,

    Thanks again for the quick response. Like I mentioned credible info is not easy to find, and unfortunately I live in a what seems to be a mecca for hack contractors. I appreciate your time.

  6. User avatar
    Dana Dorsett | | #6

    Zone 6 is cold enough for fairly substantial freeze/thaw spalling, and a foot of overhang isn't really enough to prevent direct wetting of the exterior. Together that puts the joist ends, and even the stud edges at higher moisture content, and higher risk of rot.

    Bottom line, insulating it from the exterior will be much safer, as Martin suggests.

    In zone 6 you'll need a minimum of R7.5 on the exterior where the batt insulated studwall has already been built for dew point control at the exterior side of the batt insulation. Where there is no interior insulation, it would take R15 on the exterior to hit code minimum performance, but one could also get there R7.5 on each side. If more than half of the R is on the interior it has to be a minimum of R20 total, even if the interior insulation is impermeable to water vapor.

  7. 3rd Little Pig | | #7

    It looks like I am actually more in 5A. Would you suggest the same?

  8. User avatar GBA Editor
    Martin Holladay | | #8

    Tony,
    Climate Zone 5 is certainly cold enough to cause freeze/thaw spalling on an old brick building with interior insulation.

    That said, there are lots of variables. One variable is the degree to which your brick walls are protected from rain by good roof overhangs. Another variable is the freeze/thaw tolerance of your bricks, which varies widely from building to building.

    If you are tempted to insulate this building on the interior, the work is risky. In the worst-case scenario, you can destroy the building. That's why it's worth spending $6,000 or so on consulting fees before you make a big mistake.

    All of these facts are explained in my article, Insulating Old Brick Buildings.

  9. 3rd Little Pig | | #9

    Martin,
    Thanks for the follow up. I'm actually going to take your first advice and insulate it from the outside. I was just making sure I use insulation with adequate R value. I have read the article, which is how I found this forum, (glad I did). I wish I found it before I did the other work. Can't thank you guys enough for your time and information.

  10. User avatar GBA Editor
    Martin Holladay | | #10

    Tony,
    For the areas of your house with no interior insulation, you don't really have to meet minimum code requirements (unless, of course, local regulations require you to do so on a renovation job). Any amount of exterior rigid foam would be an improvement.

    The tricky areas are those that include interior insulation. For those areas, you need to worry about the ratio of interior to exterior insulation, as Dana points out.

    The usual advice when combining exterior rigid foam and interior fluffy insulation in Climate Zone 5 is that a minimum of 27% of the total R-value of the wall assembly needs to come from the rigid foam layer.

    If your interior 2x4 walls have R-13 insulation, you would need at least R-5 of exterior rigid foam, according to this guideline. That said, the inclusion of an interior vapor retarder would allow you to cheat a little (if, for example, you decided to install R-4 rigid foam).

    For more information on these issues, see these two articles:

    Combining Exterior Rigid Foam With Fluffy Insulation

    Calculating the Minimum Thickness of Rigid Foam Sheathing

  11. 3rd Little Pig | | #11

    I will check definitely those out. Thanks so much.

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