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EIFS and WRB questions

Antonis Antoniou | Posted in Energy Efficiency and Durability on

We are at the design phase of our new home. We live in a Nicosia, Cyprus and we enjoy a Mediterranean climate with mild winters and hot summers with only a few inches of rain per year, and relative long sunny periods between wetting events (rain). Our design calls for large overhangs (4-5 feet) around most of the building, mainly for shading purposes during the summer.

Most of the construction in our country (95% if not more) is done with reinforced concrete structural members and brick walls, however we are planning of using I-beams for structural members and light gauge steel for wall framing purposes with glass-mat or cement board sheathing. Now the majority of insulation is done with a face sealed EIFS (EPS and XPS) on traditional construction and since our steel members will probably reduce the value of our cavity insulation to half its name value I am thinking that the best insulation method for our case is also EIFS. However, having read here that the face sealed EIFS is not a good idea with a wall that cannot store moisture has raised concerns. So my questions are the following:

1. Should I be worried or even avoid using face-sealed EIFS, even if it is hard to get a WRB installed? (House wrap is a new thing here and liquid WRBs, which I really like from what I read, are virtually unheard of). I am thinking that I might not be in such a risk given our weather.

2. Almost all systems of drained EIFS I have read about, call for drainage channels between the WRB and the insulation. Given that the insulation is not in full contact with the wall does this change its effective R-value?

3. All of the windows I have seen installed are held in place via screws through the sill, jambs and head of the casement. Are flashing tapes and liquid applied flashing products self healing if perforated by screws or is there a certain way that you need to treat these perforations to keep the waterproofing of the flashing.

4. What would be the best/easiest way to air seal the building envelope in my case if I use rockwool for the external insulation and synthetic stucco as a finish.

Sorry for the long post.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Antonis,
    I'm glad to hear from someone from Nicosia. (My family spent the summer of 1966 in Cyprus, hiking the mountain trails and sleeping in orchards and farmers' fields. What a beautiful island.)

    All of the EIFS problems that occurred in the U.S. happened in wood-framed buildings. The problem was the wood framing and the OSB sheathing, not the EIFS. If your house has steel framing, it won't be at risk for rot.

    Your instinct to put all of the insulation on the exterior side of your framing is a good instinct. That's where the insulation belongs.

    If any moisture enters the stud cavities of your steel-framed house, the moisture will evaporate readily to the interior. But I don't anticipate any moisture entry, for three reasons:
    1. Your house will have generous roof overhangs.
    2. Your insulation is mineral wool, which is itself a material that allows moisture to drain harmlessly on the exterior of your wall assembly.
    3. Rainfall totals are low in Cyprus.

    If Cyprus has EIFS contractors, I would trust the EIFS contractors, and allow them to follow their usual methods. That said, if you can find any peel-and-stick flashing products at local building supply outlets -- something like Vykor or Ice & Water Shield -- you might want to install this type of flashing on the window rough openings before the windows are installed.

  2. Steve Knapp CZ 3A Georgia | | #2

    Building Science Corporation (https://buildingscience.com/glossary/eifs) has a couple of documents on EIFS. The authors are pretty negative on the system for the reasons Martin outlined--except when it is used in a warm, dry climate (as is typical in Cyprus).

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