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Is anyone familiar with the Hunter Panel Xci NB insulated panel?

skersey | Posted in Energy Efficiency and Durability on

We are planning a new home with our retirement in mind and working for an electric utility I fully understand energy cost are not going down, so I have been studying wall assemblies. I have decided on standard stud construction with 2″ polyiso foam on the exterior with either fiberglass batts or sprayed celulose in the cavity. The 2″ foam layer meets the Zone 5 requirements according to the information I have been using from this site. The sheathing will be Hardy board or similar product applied over furring strips to provide exterior moisture control. This method seems to be a little cumbersome to install and will require OSB or a structural foam board under the polyiso layer. I have concern about the layer of OSB holding too much moisture but with the correct living space ventilation I believe this can be resolved.
I recently learned about the Hunter Xci NB insulated panels that seems to provide a feasible option providing the 2″ continuous external insulation, eliminates the need for the OSB under the foam layer, moves the drainage plane to the outside of the foam layer making window flashing and installation easier, and overall appears to be a simpler, cleaner installation than using separate OSB and polyiso products. Furring strips would be easier and less expensive to install due to shorter fastners. It is also considerably cheaper per sq ft than the foam and osb as separate components, $1.85 vs $2.48. Here is the link to the info page at Hunter panels:
Even though these panels are a reasonably new product for use on vertical walls, this company has successfully used this basic assembly for many years in the commercial roofing industry. What kind of issues should I anticipate with the use of these panels? Does anyone else think they address the various installation issues related to using external foam board, or have I overlooked some important factors?


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  1. GBA Editor
    Martin Holladay | | #1

    The only thing I can think of that you should pay attention to: make sure that your local building inspector or your engineer agrees that your chosen sheathing panel provides enough bracing for your wall. If it doesn't, be prepared to include an alternate bracing method (for example, L-profile steel strapping).

  2. Expert Member
    ARMANDO COBO | | #2

    Thanks for bringing up this product. It appears to have similar properties as the Huber Zip R Panel but with Polyiso (higher Rvalue), up to 2” thick, and less GWP (good timing with Alex Wilson's blog). The tech engineer is on vacation this week, but maybe next week we'll find out if they have ICC approval for structural sheathing or if they provide their customers with an engineer's report. Until then, like Martin said, you should plan on bracing your walls, plus you need to make sure the Plwd/OSB is taped, and install a WRB on top. I’m still concerned with condensation on cold substrates as well, like in the Zip R panel.
    The good thing is that with Dow’s SIS, Huber’s Zip R and Hunter’s XCI-NB panels we have more choices, but they differ from each other in some properties. It’ll be wise for builders to understand the differences for the right application. To be continued next week…

  3. skersey | | #3

    I will definately check into the bracing question before we proceed, but it shouldn't be a problem to add that in if needed.

  4. skersey | | #4

    I am planning on using a WRB on top and taping the joints as suggested, although I had considered using spray foam from a can to seal between panels since the 2" edge of the foam board would make this possible.
    We are in west central Indiana (zone 5), so is your concern about the condensation lessened if 2" of foam is used? I had contemplated using the Dow SIS against the studs, then placing the 2" panels over that. This would add a step in the installation and be more expensive, but would add considerable strength plus an additional R-5 to the assembly. Any thoughts on that?

  5. Expert Member
    ARMANDO COBO | | #5

    Interstitial condensation, on cold Plwd/OSB sheathing, happens when the interior of the exterior sheathing is colder, or lower temperature, than the dewpoint at an X°F temperature and Y% relative humidity; so we need to warm the framing cavity.
    A simple way to calculate the dewpoint risk is by ASHRAE Fundamentals. It’s not perfect and it is very conservative, but it creates possible warnings for wall and roof assemblies. Or you could pay someone to do a WUFI analysis for you.
    - Doing those calculations for Indianapolis: 70°F – 40% RH – 45°F Dewpoint, Average temperature for coldest 3-months is 26°F.
    1. On a 2x4 wall and 2” rigid foam OUTSIDE of the sheathing is fine.
    2. On a 2x6 wall and 3” rigid foam OUTSIDE of the sheathing is fine.
    If the interior temperature and RH goes up, then it makes it worse. So now the question is, how are you going to control those interior temperatures and RHs for the life of that house?
    The big problem I see with Huber Zip R and Hunter’s XCI-NB panels is that you are adding rigid foam on the INSIDE of the sheathing, thus making it impossible, in my opinion, to keep the Plwd/OSB sheathing warm.
    I asked that question to Huber 6 months a go, and never got an answer. I’ll be asking Hunter’s Engineers the same question. I wish Peter Yost, Dr. Joe or Bill Rose address this issue of Zip R and XCI-NB panels for us, and settle it once and for all.
    That’s why I do not specify those new panels, and untill I get a satisfactoty aswer, I'll recommend SIS panels or outsulation.

  6. MJDesigns | | #6

    The Zip R should work fine in Indianapolis (Zone 5) with an R-value of 6.6 if 2x4 construction were utilized as the minimum requirement is an R value of 5 to keep the inner wall cavity safe ... fill the remainder of the cavity with 3 1/2" of blown fiberglass or cellulose and you'll have a decent wall that's thermally broken. However, it's too risky for 2x6 as the recommended minimum is 7.5 and it's only available up to 6.6 so at certain times of the year, as Armando points out, there's risk and extra care required to keep the indoor relative humidity low. A recommendation would also be to utilize an exterior water resistant barrier such as Benjamin Obdyke's Hydrogap to provide a drainage space between your cladding and the Zip R sheathing as an extra precaution against poorly applied Zip tape and a more secure way to flash your windows properly. The Zip R sheathing when utilized with the Zip tape and an additional WRB on top of it will provide you with a great air seal at the exterior of your home.

    Agree with Armando ... would really love the experts to weigh in on the Zip R product as well. I do know that Dr. Joe approves of the regular Zip sheathing. Martin has weighed in on this topic in the past as of late and has some reservations based on the maximum R-value (6.6) currently available as it really limits the applicability to many of the colder climate zones.

  7. GBA Editor
    Martin Holladay | | #7

    My opinion is that you still need to have a thick enough layer of foam to keep the stud cavities above the dewpoint. My own guidelines for calculating minimum foam R-values are here: Calculating the Minimum Thickness of Rigid Foam Sheathing.

    I'm not too worried about the fact that the OSB layer is on the cold side of the foam -- as long as you include a ventilated air gap between the OSB and your siding. That way, if the OSB gets damp during cold weather, it has a fast way to dry out.

  8. skersey | | #8

    I understand the need to keep the sheathing tempurature warm when it is underneath the 2" of foam, but I do not see the need if it is outside of the foam. Shouldn't the main concern still be the inside of the wall cavity? I would be covering the panels with a building wrap and attaching vertical strapping(furring strips) to the sheathing of the XCI-NB panel to provide the ventilation for both the sheathing and the Hardi Plank siding. Shouldn't the drying for the sheathing in this case be to the outside and not affect or be affected by the internal wall temperature or moisture content?

  9. skersey | | #9

    Having lived here for 50+ yrs I am not much of a fan of minimum levels of anything when it comes to our weather! We have had some pretty intense winters in the past, so I am sure they will return someday. I do agree with everyone's apprehensions when it comes to relying on any kind of tape or mastic to last as long as the house, so I will be using some kind of wrap. I have briefly looked at the Benjamin Obdyke's Hydrogap and that sounds like a real possibility.

  10. skersey | | #10

    I believe it was your calculations that I used to determine the thickness of foam to use. Thanks so much for providing that informtion as it was very useful and I am sure I couldn't have done that myself. As you will read in my last posts, we seem to be on the same page concerning the placement of sheathing on the outside of the foam!

  11. Expert Member
    ARMANDO COBO | | #11

    I disagree no having outsulation or calculating the minimum outsulation by code; it assumes that your Climate Zone 5 in Indianapolis has the same building solutions as the Climate Zone 5 in Boston, Chicago, Omaha, Taos, Reno and Spokane; which it does not. I know everyone does not share the same enthusiasm for doing dew point analysis as I do, whether by ASHRAE or WUFI, but if I’m going to err, I’ll rather err on the side of caution; plus it’s cheap insurance, lowers my risk management, and my clients get really good job performance. Try doing those analysis on those cities, just once, and you’ll see the big differences.

  12. Expert Member
    ARMANDO COBO | | #12

    Another thought... Building Codes are moving on to increase insulation and outsulation for a reason. I rather be ahead of codes than following.

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