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Continuous Insulation – Part 1

April 7, 2011

This series of posts is definitely for my architecture/construction readers, unless you’re so inclined . . .

As most design professionals know, everything in the field of construction is moving to create more energy efficient buildings. At first, this was a fringe movement that led to standards such as the LEED program developed by the U.S. Green Building Council (USGBC). As the movement has gained momentum, more and more of the standards are becoming a part of local building codes. Certain jurisdictions are requiring some level of LEED certification for buildings. Locally, the City of Baltimore has developed their own Green Buildings Standards as a requirement or alternative to LEED.

Additionally, the International Code Council has begun implementing more “Green” building practices into their family of codes. First, they introduced the “International Energy Conservation Code.” Now, they are working on an “International Green Building Code.”

With the 2009 editions of the International Energy Conservation Code (IECC), one particular requirement has raised significant questions and problems within the building envelope. This term called “Continuous Insulation,” often just a little “ci” in the codes is beginning to make a stir and, if implemented properly, will change the way we build . . . but it is RARELY implemented properly at this point in time . . . and thus this series of posts.

First – what is Continuous Insulation, and why is it such a big deal?

Let’s begin with the second half of the question . . . While CI is used in a variety of wall assemblies, it is most important where materials of high-conductivity are used . . . especially metal.  For instance, historically, we would install batt insulation between metal studs and move on.  However, in a metal stud wall, the studs conduct so much heat, they reduce the total R-Value by about 50% (depending on specific factors). So your average stud wall (4″-6″ studs) results in a maximum R-value in the R-7 to R-9 range. If CI is used and installed properly, you get approximately the true R-Value of the material.  So what is it?

The IECC 2009 actually does not define the term, but they pulled it from ASHRAE 90.1. ASHRAE 90.1 defines Continuous Insulation as insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building.

With further research, you discover that “fasteners” is meant to include screws, bolts, nails, and the like, but not much else.  This means furring strips, clip angles, and other large connectors are generally excluded . . . which is where the big problem lies, and why I spent time doing the research.

If you are using a self-supporting cladding such as brick or other masonry, you can use a system of ties that meets the “fastener” requirement and move on.  If you are using a continuously insulating system, such as Insulated Metal Panels or EIFS, you also don’t have a problem (provided they truly are continuous and without thermal bridges). But for any cladding material supported by the building structure, significant problems occur.

For most regions of the country, the IECC 2009 is now requiring R-7.5 or more of CI on metal-framed buildings. In general, this will be 1.5″ or more of insulating  material (depending on the specific material used). However, most Cladding Systems, such as Metal Panels, Cementious Siding, etc are only approved for attachment through 1″ of non-supporting material.

If you go to most of these cladding companies’ web sites to find out how to install their product over a thicker insulating layer . . . you will almost universally find a detail similar to the one shown here, which has a metal Z-purlin passing through the supposedly Continuous Insulation to get to the structure.  Some suggest using a “Thermal Break” at the connection to the structure.  From the research I’ve found, you have still reduced the effectiveness of the CI from between 25%-50%.

As a result, I spent 3 days calling various cladding manufacturers, rigid insulation board manufacturers, and several other industry-related people, while doing online research, code analysis, and more . . . And I finally have some true and good solutions . . . so we’ll pick up there in the next post.

Feel free to contact me at Curry Architects if you need design help in any way.

10 Comments leave one →
  1. April 8, 2011 8:58 am

    Thanks for addressing this, Andrew. I haven’t directly encountered CI issues yet – now I can be prepared. I’m looking forward to your next post.

    • April 8, 2011 8:07 pm


      Alabama has adopted AHSRAE 90.1-2007, which has almost identical requirements to IECC 2009 as it relates to the building envelope.

      This is one of my reasons for posting . . . it is highly adopted, but rarely enforced.

      In Baltimore County, the architect is required to sign a document stating that the building complies with IECC 2009 . . . but the building official is just now starting to understand IECC enough to enforce it . . . but since architects need to sign the document, if it doesn’t actually meet the code, the architect is liable whether the code official enforces it or not . . .

      SO, you may think you haven’t encountered it yet, but you may want to double-check your local codes being enforced on your current projects

      If you’re doing residential and/or wood construction, the CI requirements are much lower, so the construction methods are not nearly as difficult to achieve.

      • April 9, 2011 7:46 pm

        I haven’t encountered it yet…

        All of my work to date with CASA Designs has been Corp of Engineer task orders for the U.S. Army. The “austere” facilities we are developing are for use in overseas deployment and don’t even HAVE insulation, much less CI.

        (This admission may disqualify me for further consideration with Curry Architects, but with a son in the Army it feels like an appropriate expression of my design efforts!)

        Nevertheless, I do look forward to your next posts. Some day I hope to employ the CI information. Thanks.

      • April 10, 2011 12:06 pm

        I don’t see how the work you are doing could possibly disqualify you for any job. I did some side work last year for Haiti. Not great design, but challenging, as it had to be disassembled and fit into a shipping container to be reassembled in Haiti. Our office thought the concept was really cool.

        I didn’t mean to minimize your experience.

  2. April 8, 2011 9:21 am

    Don’t forget that the continous insulation also increases the durability of the building as well with increased tightness and a more effective way to control moisture.

    • April 8, 2011 7:58 pm


      Thanks for the added info related to the value of CI. My purpose for this series is not to give all the reasons WHY for CI, but to deal with the HOW. A few more of the WHYs will undoubtably come up in the following posts as I describe the HOWs. I wouldn’t be pressing so hard on getting it right if I didn’t see real value in doing it. I believe it is DEFINITELY a great thing for buildings.

  3. June 3, 2013 5:04 am

    An outstanding share! I’ve just forwarded this onto a colleague who has been conducting a little research on this. And he in fact ordered me breakfast simply because I stumbled upon it for him… lol. So allow me to reword this…. Thank YOU for the meal!! But yeah, thanks for spending the time to discuss this subject here on your web site.


  1. Continuous Insulation – Part 2 « APK's Attic
  2. Continuous Insulation – Part 3 « APK's Attic

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