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Opinions on Exterior Insulation Finishing System (EIFS) on Brick House

RayT_817 | Posted in General Questions on

I am considering purchasing a pre war brick (structural) house in climate zone 4. I’m not sure what the insulation situation is on the inside, I am considering adding exterior insulation in the form EIFS after applying a liquid wrb. I’m basically following the figure 4 in this article https://www.buildingscience.com/documents/digests/bsd-114-interior-insulation-retrofits-of-load-bearing-masonry-walls-in-cold-climates.

Does anybody see a problem with this? Also is an air gap needed anywhere?

 

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Replies

  1. Expert Member
    Dana Dorsett | | #1

    With an EIFS finish and a spray applied WRB on the brick there is no need for an air gap, as long as the interior finish wall is reasonably vapor permeable (= no vinyl or foil wallpaper- stick with standard interior latex paint, etc.

    The most important thing to get right is the flashing or bulk water management details at the window. Depending on how the window openings were built the liquid WRB and the indents of the mortar channels in the brick would be more than adequate, or there may need to be a bit of rework around the windows to ensure proper drainage either to the exterior of the foam or the exterior of the WRB. If the surface of the exterior was made unusually smooth (like a poured concrete wall) there are EPS products manufactured with drain channels built in, but that's a cost adder that most brick walls would not need. eg:

    https://www.insulfoam.com/foundation-insulation-drainage-board/

    In zone 3 with continuous foam on the exterior of a masonry wall it only takes R8 to hit code min, but R12 (or even R16) wouldn't necessarily be insane, depending on your performance goals and how much roof overhang you have to work with and other possible limitations of geometry, say windows close to an inside corner, etc. See the "mass wall" column in TABLE N1102.1.2:

    https://up.codes/viewer/nevada/irc-2018/chapter/11/re-energy-efficiency#N1102.1.2

    The cost of fatter foam can be minimized (and verditude of the project maximized) using reclaimed roofing EPS, often available from reclaimers at a quarter to third the cost of virgin stock foam. That is 3-4" of EPS for the price of 1" virgin stock EPS. There is effectively zero additional environmental impact when using reclaimed foam- it's just piling on to the benefit side of the environmental cost ^ benefit balance on environmental hits already taken.

  2. Expert Member
    AKOS TOTH | | #2

    Use foam grooved on the back for drainage, most EIFS installs already spec this. This allows for any liquid water to move down along the WRB plus allows for a bit of drying.

    There is a lot of EIFS over brick around me (zone 5) and as long as it is installed well (grooved foam, WRB, window flashing) it works great.

    Sometimes it is a shame to cover up nice brick, so I would only go down the EIFS road if your brick is in very bad shape or very ugly.

  3. Expert Member
    PETER G ENGLE PE | | #3

    Dana addressed the grooved foam issue above. It is really not necessary when installing EIFS over brick, as the mortar grooves in the brick serve the same function. Either a roll-on or spray-on WRB can work on brick behind an EIFS skin. The big challenge is getting the details right around the openings, but otherwise, this is not a difficult retrofit and it will provide substantial additional insulation. The EIFs manufacturers generally have several different levels of protection, with additional drainage and water management capacity for each one. Unless you are in a heavy wind-driven rain location, flat foam over brick should be fine and should meet the EIFS manufacturer's installation instructions for residential construction.

  4. RayT_817 | | #4

    Thank you all for the quick responses. I have several follow ups questions, but here is some additional information about the house which is in the NYC suburbs.

    - The house has a asphalt shingle pitched roof and an uninsulated, unfinished attic that has insulated HVAC ducts running through it. I would like to finish sometime in the future.
    - The basement is fully finished, but I am unsure of the details involved.

    Does the roof/basement need anything done or can I simply add the foam/EFIS on the visible portions of the exterior wall?

    Do the windows have to be removed and reinstalled for this project?

    @Dana Dorsett - I'm very new at this and most of the contractors that I have hired before only do interior work. Do EFIS contractors allow for sourcing your own foam and how would I verify the bulk water around the windows are properly done?

    @Akos - The exterior brick actually looks like its in pretty good shape and I would like to keep it if possible. However, I have neither the time nor the funds to do a full gut remodel of the interior as it appears to be well kept. My main goal is to avoid a drafty energy sucking house using the least intrusive and risky renovation method possible. Do you have any alternative suggestions to achieve this?

    1. Expert Member
      AKOS TOTH | | #6

      I was in a similar boat before, didn't want to take out interior walls or cover the brick. Ended up working on air sealing the place and replaced most windows with triple panes. Firgured the extra cost of triple pane was less than doing any insulation work, with largish windows, it did significantly improve the walls overall R value.

      Overall the house was significantly more comfortable and way more energy efficient. About the only spot you could feel the house was not insulated is one of the rooms that was had exterior walls on three sides.

      I figure if the walls ever need to be demod down the road, can insulate at that time with a thin layer of SPF from the inside.

      P.S. The window replacement was brick to brick, so the old leaky rough framing was also taken out. This did mean interior trim work but allowed for larger windows and much better air sealing.

  5. Expert Member
    Dana Dorsett | | #5

    >"- The house has a asphalt shingle pitched roof and an uninsulated, unfinished attic that has insulated HVAC ducts running through it. I would like to finish sometime in the future.
    - The basement is fully finished, but I am unsure of the details involved.

    Does the roof/basement need anything done or can I simply add the foam/EFIS on the visible portions of the exterior wall?"

    The basement and attic are still major air and heat leaks that need to be treated to be able to control heat & moisture movement inside the house. Being able to control both heat and (air transported) moisture flows has major effects on comfort and indoor air quality.

    #1: The attic floor/upper floor ceiling needs to be air-sealed. Ideally this would be tested & verified by blower doors & infra-red cameras. This is a large topic with lots of particulars, but every plumbing, electrical & flue penetration needs to be sealed, as well as the top plates of the partition walls & finish walls.

    #1.a : The ducts and air handler in the attic need to be air sealed on EVERY seam & joint, and all duct boots need to be air sealed where they penetrate the ceiling plane. For ceiling registers it's often easier to air seal the seams in the duct boots and seal the duct boot to the ceiling from the room side rather than the attic side. Use duct mastic (not tape) to seal the seams of the duct boots. Use polyurethane caulk or expanding can-foam to seal the duct boot to the ceiling, then trim the sealants flush and tape over the sealed gap with a UL 188 rated HVAC tape, adhering it to both the inside of the edge of the duct boot and the ceiling.

    #2: Air seal the basement. This may be tough to do in a finished space, but at the very least verifying the air tightness of the basement doors & windows, as well as any flue or plumbing/electrical chases that extend from the basement to the attic are critically important.

    #3: Decide what you're going to do with the attic long term. Insulating at the roof deck and sealing up the roof vents would be ideal whenever there are ducts in the attic, but it's expensive. If the attic floor has been well air-sealed, the next best thing (and much more affordable thing) to do would be to install 15-17" of blown cellulose on the attic floor. That's usually deeper than the pre-existing joists, and sometimes it's best to build a catwalk/platform for servicing the HVAC equipment, or installing a second set of joists perpendicular to the existing joists to support an entire floor deck for storage, etc. A milled 2x10 joist is 9.25" deep- installing a set of perpendicular 2x8s (7.25" deep) and filling it up to the new joist tops gives you sufficient depth. If the original joists are 2x4s or 2x6s you'd have to adjust accordingly.

    #4: If not gutting the basement for air sealing and insulating all the way down to the slab with the code min R10 continuous insulation (or a 2x4/R11 batt insulated wall snugged up to a a half inch of any foil faced foam against the foundation wall), digging down to 2 feet below grade and installing EPS on the exterior would be the next-best thing. Below grade the code minimum for zone 4 would be R10, (2.5") but it's fine to go fatter.

    I don't have enough experience with EIFS contractors or any contractors in Westchester & Long Island to know how likely it is to find somebody willing to use reclaimed foam. Ask them if they have sources of used or factory seconds EPS they regularly use, and let them know you're open to that, especially if there's a price break for going that route. Factory-seconds foam is usually rejected for cosmetic problems, like dents or dinged corners, sometimes for thickness that is out of spec. But a house has enough windows & doors that the scrap rates are high, and modestly damaged foam can usually be worked around, with the damaged portions being the window or door cut-outs. Truly minor dings can be ignored, or filled in with can foam and trimmed flush prior to the EIFS coat.

    I would hope most EIFS contractors would understand how window flashing works and adjust the installation accordingly. If the windows are old and leaky it might be worth replacing them as part of the project, but that's rarely cost effective. A tight low-E storm window over tightened-up single panes will perform about as well as a new code-minimum window. If the sills & window bucks are going to be extended to accommodate the thickness of the foam, flashing the extension and adding a low-E storm roughly co-planar with the EIFS layer ("outie" style) can reduce the risk of bulk water incursions by quite a bit.

  6. tommay | | #7

    Pre war? Which war are you referring to? If it is revolutionary, you gotta wonder how all those who have lived there in the past and up until today, survived. Having worked in lots of homes in revolutionary towns, around where the shot was heard around the world, I've seen how solid and massive they can be, even if they are smaller homes, and how most are solar orientated correctly. Even layout and windows provide natural light and ventilation and cooling, especially if there is a basement and / or attic space. They knew what they were doing back then and did it without mechanicals.
    If you decide to purchase this home, live in it for at least a year and see how it feels, see/learn how it works, then decide what needs to be done.

    1. Mark_Be | | #8

      In the NYC area, the war in pre-war generally refers to WWII.

    2. RayT_817 | | #10

      The house was built in the late 1930's. Pre WWII (or at the beginning of WWII depending on what part of the world you are from).

  7. RayT_817 | | #9

    Thank you all for providing advice. We decided not to go with the house after reviewing the project list and the inspector telling us the electrical might need to be updating also. It was also unknown whether there was lead paint on the walls.

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