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Community and Q&A

EIFS reviews?

David McNeely | Posted in Green Building Techniques on

I am wondering why EIFS is almost never mentioned in this website. It seems to offer it all: a spray-on or rolled-on WRB that also performs as an air barrier; a drainage plane; outsulation that also provides a thermal break; a finish surface that doesn’t require painting. Talking to my local installers, I’ve learned that 4” of foam costs little more than 1”. Adding 4” of EPS to a 2×4 bay with dense-pack or sprayed cellulose results in about an R-29 wall assembly that is relatively economical. If one opts for “innie” windows at the drainage plane, this wall assembly seems to be simpler to build than many that are advocated in these pages again and again. Getting it to airtight also seems straightforward.

So my question is, why is this system not suggested as a great alternative?

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    David,
    If you perform a search for "EIFS" at the GBA website, you will get more than 50 links.

    The GBA Encylcopedia has an entry for EIFS: "Exterior insulation and finish systems (EIFS) are essentially one-coat systems, but the marriage of a stucco finish to exterior rigid insulation brings with it different water-management details than the other two types. EIFS claddings consist of synthetic stucco applied over an insulating layer of rigid polystyrene insulation. Insulation can be up to 4 inches thick. EIFS has many energy advantages over conventional stucco."

    You can read more here: Stucco and Synthetic Stucco.

    EIFS got a black eye in North Carolina because early systems were face-sealed systems rather than water-managed systems. When installed over OSB, face-sealed EIFS installations often trapped water, leading to OSB rot, especially in homes with interior polyethylene.

    The EIFS industry responded to the North Carolina disaster by developing water-managed EIFS. These systems peform very well, and I often recommend EIFS as the best way to insulate an existing multi-wythe brick building.

    The biggest problem with the current generation of EIFS is that the synthetic stucco layer is easy to damage. Many EIFS-covered commercial buildings are dented from impacts. These dents look shabby.

  2. J Chesnut | | #2

    It is not so clear to me that "water-managed EIFS" act as the WRB and air barrier. I think instead it should be considered just cladding. The detailing for EIFS on stud wall construction includes a drainage plane behind the rigid foam backed by a WRB. The drainage plane is a 1/4" plus unsealed air gap. This unsealed air gap exists between the outside insulation and the sheathing so the rigid foam isn't acting as the air barrier. I wonder also if the drainage space compromises some of the R-value of the assembly.

  3. David McNeely | | #3

    J Chestnut,
    Dryvit includes "Backstop NT" —a flexible, polymer-based coating that provides a watertight membrane and air barrier. The air gap is sealed with a drainage track that presumably keeps out insects. Your question about compromising the insulation value of the foam has been a concern to me as well, and I have not seen it discussed either here or at BSC.

    Martin,
    Thanks for your response. I did search these pages and had read most of the links, including the one you mentioned. I meant to say I don't see it in these Q&A discussions, where the people who are actively engaged in conscientious building regularly advocate for their favorite systems.

    I have noticed that it feels soft to the touch, and a little "fake" therefore—although not as fake as vinyl siding. I can believe that it would dent as easily as well. For an upcharge there is an impact-resistant surface available, intended mainly for hurricane areas. Do you think this would feel and perform more like real stucco?

    I must say I find it very appealing to not have to worry about the endless details involved in creating a rainscreen between polyiso and siding! Training and managing the carpenters I've met recently would require more of my time than just doing it myself. (Not to digress, but I do wish there was a better training system for trades, and some way to make "journeyman" and "master" actually have meaning.)

  4. J Chesnut | | #4

    David,
    I have worked on a residential home with EIFS that was applied directly to ICF construction (w/o a drainage plane).
    The resistance to damage may be more a property of the EPS foam than the thin synthetic coating. Higher density foam is available at higher prices.
    I don't think the "water managed EIFS" represents a system that is easier to detail. Detailing primarily involves shedding bulk rain water. With EIFS you still have to tie all the flashing at windows and doors back to the drainage plane behind the EIFS cladding. US EIFS manufacturers specify 3/4" caulk joints where the EIFS meet different conditions (one example at the window return), an aesthetic item to pass by the client.

    Dryvit's "Backstop NT" is a wet applied WRB that can be used with any cladding system. The drainage track does not seal the air gap because the air gap has to be able to release any bulk water intrusion back to the outside via the flashing. My bet is you would find yourself spending more time on details because residential contractors rarely have experience installing EIFS and therefore do not have default details to work from. That was my experience as a designer on the aforementioned project.

  5. Expert Member
    Armando Cobo | | #5

    I don’t mind specifying EIFS stucco, and I do it often; but one thing I’ve learned is that all manufacturers of EIFS I know have their own installation instructions that must be followed to the “T”; but many installers want to do it their own way, and sometimes that’s where the issues begin.

  6. Skylar Bowker | | #6

    David & J - High Impact (or "Heavy Duty" or "Panzer") Mesh can be embedded into a second layer in the basecoat where required. This is typically the first 6 feet around areas that have walk-by traffic, and significantly increases the impact resistance of Exterior Insulation Finish Systems.
    You can read more: Can EIFS be made more resistant to damage

    All EIFS manufacturers have a product similar to Dryvit's Backstop NT that should be installed between the drainage layer and wood sheathing. Note that it's an air barrier, not a moisture barrier to prevent water from becoming trapped.

    Skylar

  7. Michael Chandler | | #7

    We compared EIFS to lath and conventional stucco and the price was much higher for the EIFS in our area.

  8. David McNeely | | #8

    Michael,
    Did your conventional stucco price include a drainage plane and insulation—i.e. was this comparing apples to apples? Because this is a very wet area (almost 50" average) I like the idea of more than just a crinkled layer of tarpaper to serve as the drainage plane. Mold is a serious issue in almost every house I've looked at.

    In my area EIFS with backstop & foam is about $6.60/sq.ft. Stucco is up to $7.00.

  9. J Chesnut | | #9

    Skylar,
    Thanks for the correction concerning the impact resistance using the stronger meshes.

    True that the Dryvit Backstop NT and similar products help establish air barriers but I do believe they are engineered to function as the WRB. I think when you say they are not a moisture barrier maybe you are referring to their perm ratings.

    If I recall correctly there are both "vapor open" and "vapor closed" formulations. As a backing for the drainage plane they must function as the WRB, no?

    Still curious how the drainage plane behind the insulation affects the effective R-value.

  10. Michael Chandler | | #10

    David
    I was comparing BASF EIFS on foam over wrinkle wrap and OSB to conventional two coat stucco w/ paint on Spider lath over two layers of tar paper on wrinkle wrap on OSB. even discounting the cost of the foam and getting an employee discount on the BASF EIFS mix it was cost effective to go with conventional stucco.

    I'm in North Carolina countryside so our masons are comfortable w/ traditional stucco and resistant to that new modern I-fuss stuff and that may have been the major issue here. Our EIFS contractors come from the big city, drive fancy trucks, and mostly work on big commercial jobs, stucco guys generally lay cinder blocks but will do stucco too if you do all the lath and water proofing and set the grounds and weep screeds before they get there. Generally I have to buy the sand and mortar too as these guys barely have enough credit to maintain workers comp and payroll taxes, but they get the job done well for a good price.

  11. Tyler LeClear Vachta | | #11

    J Chesnut,
    When drainable EIFS was introduced they determined that keeping the drainage gap at 1/8" created the necessary space for a capillary break (if the gap was consistent) and maintained 95% of the insulation's effective R-value. You're right, the further you move the insulation out from the wall the less impact it will have.

    Dryvit and other systems have included a corrugated drainage strip at the terminations to prevent the drainage gap from being sealed off.

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