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Energy-Smart Details

Nailbase Panels for Continuous Insulation

The flexibility of nailbase panels makes them useful when retrofitting existing walls for better energy efficiency

Here at Just Housing, we integrate nailbase panels into our assemblies because we like their flexibility when it comes to installing continuous insulation on both new construction and retrofit projects. Nailbase panels are rigid foam panels with a layer of OSB or plywood glued to one side; they provide sheathing and foam insulation in a single product. Here we will look at their application in a wall assembly, but nailbase panels can be used in roofs too.

New construction method

Our standard Just Housing wall demonstrates the application of nailbase panels in new construction. This assembly has 2×4 or 2×6 studs with structural plywood sheathing sealed as the air barrier. The plywood is then wrapped with a layer of nailbase panels. We design the drainage plane to the outside of the nailbase panels and specify a water-resistive barrier (WRB) sheet good installed shingle style, integrated with window, door, and base flashings.

Real-world retrofit

For retrofits where new siding is planned, nailbase panels work well for installing continuous insulation, and they can be integrated whether or not the windows are replaced. That said, it is critical to ensure the new nailbase panel is compatible with the rest of the existing assembly.

Nailbase installation

The retrofit project pictured here benefitted from the use of nailbase panels. The owners were uncomfortable in their leaky, underinsulated 1960s ranch home, and their energy bills were high, but they loved their house and its location. They—and the house—were ready for some improvements.

The existing wall assembly included 2×6 studs sheathed with T1-11 plywood; installation was too close to grade, which resulted in rotting structural wood. Conditions included a former attached garage that had been converted to living space; it was insulated with closed-cell spray foam. The rest of the house had poorly installed fiberglass insulation. The presence of…

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  1. Expert Member
    Michael Maines | | #1

    Good ideas. I would love to see wood fiber nailbase!

    When it comes to moisture-related concerns, I use the most conservative values for foam insulation. We know that eventually, all closed-cell foam products, including polyiso, will have the blowing agents in the cells replaced with air, which is R-5.6/in, and we know that polyiso performs worse at low temperatures, which is a dynamic value and impossible to pin down, but I would not over-estimate the R-value because even if it works well today, eventually--whether 10 years or 30 years--it won't perform the same way.

    Conversely, when it comes to meeting code-required thermal envelope values with foam, which has high levels of embodied carbon emissions, I use the highest R per inch published.

    1. JustHousing | | #2

      Nice to hear from you, Michael! Like you, we adjust the R-value per inch in response to whether it's performance analysis vs required documentation to meet code requirements ... we couldn't figure out how to write that into the article, so thanks for bringing it up. And yes, we also hope to see wood fiber nailbase products on the market.

  2. BirchwoodBill | | #3

    Some of the Neopor / GPS products approach RSSi 5.4 around 25F. Interesting chemistry with putting Graphene into the mix. Will need to apply some wax to a nail base panel and slide down Spirit Mountain to test the friction coefficient. :)

    1. Expert Member
      Michael Maines | | #7

      All common types of insulation perform better at low temperatures than at high temperatures, with the exception of polyiso foam. R-value is measured at mean 75°F.

  3. conwaynh85 | | #4

    Good article. What are some if the manufacturers and dealers for these panels in new england? What is the pricing range? Thanks

    1. JustHousing | | #5

      We're located in Minnesota, so I can't speak to dealers in New England, and I don't know a lot about manufacturers in your region. The companies I'm most familiar with who manufacture nailbase panels are Hunter, Atlas, Insulfoam, Porter Corp, and Huber. Hunter is headquartered in Maine and does have a manufacturing facility in the state. Hope that helps.

    2. Deleted | | #6


  4. stevehallarchitecture | | #8

    I'm curious what others think about fastener conductivity (thermal bridging) through the nail base insulation. By my calcs, one fastener per SF (Atlas recommends between 15–50 per 4'x8' sheet) has the same conductivity as the remaining SF of EPS. So practically, an R-6 sheet is adding R-3.

    1. Expert Member

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