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Continuous Insulation

  • 1.  Continuous Insulation

    Posted 10-15-2019 07:20 AM

    I'm currently working on continuous insulation wall details for a residential design and would prefer to keep the exterior sheathing against the studs for lateral structural design needs. Does anyone have experience with locating the CI on the interior side between the studs and gypsum wall board?


    J.H. Dickerson, AIA

    Dickerson Architecture

    Monroe, NC


  • 2.  RE: Continuous Insulation

    Posted 10-16-2019 05:44 PM
    J.H. -

    I am in Lafayette, LA.  We have a moderate to very warm climate here, and we have high humidity almost all of the time.  I don't know what your typical weather conditions are, but down here putting continuous insulation on the inside face of the exterior wall studs would not be a very good idea.  Almost guaranteed to create mold problems down here.

    However, I have occasionally put structural sheathing on the inside face of exterior wall studs to get lateral structural stability and that seems to work quite well.

    Because of our humidity issues, lots of common practices in northerly locations don't work for us.

    Just sayin.

    Knobbie Langlinais
    d+b Architecture

    Norbert Langlinais AIA
    AIA South Louisiana
    Lafayette LA

  • 3.  RE: Continuous Insulation

    Posted 10-21-2019 11:01 AM
    The issue is where is the weather barrier, what is the amount/type of insulation and where is the dewpoint?

    Condensation will invariably be challenging to dissipate with insulation on the inside. ASHRAE 90.1 is mandatory in 37 states which requires 25%-33% of the insulation on the building exterior to avoid condensation and mold problems.

    Sheathing on the interior to stiffen the wall is a structural matter external to that of the insulation and condensation/ mold issues.

    William Eberhard AIA
    Managing Partner
    Eberhard Architects LLC
    Cleveland OH

  • 4.  RE: Continuous Insulation

    Posted 10-21-2019 11:08 AM

    You'll want to use a German software nicknamed "WUFI" which calculates the dewpoint in walls and can tell you if the thermal envelope you are planning will work.  The colder the climate, the more outsulation you need.


    Doug Walter, AIA


    2019 Master Design Award Winner, Qualified Remodeler

    First Place , NKBA Rocky Mountain Chapter Peak Awards 2019

    Contributing Editor, Pro Remodeler Magazine

    Named one of KBDN's "50 Top Innovators"

    Sent from Mail for Windows 10


  • 5.  RE: Continuous Insulation

    Posted 10-16-2019 09:19 PM
    Well then it wouldn't be continuous insulation , as it only seals the stud bays. Airtight yes, but not continuous.  Have you looked at Huber's Zip System R panel, a polyiso bonded to their proprietary green sheathing, with foam from 1 to 2 inches thick.  You use long fasteners to screw thru foam into studs, but it is structurally rated and does a fabulous job.

    Douglas Walter AIA
    Denver CO

  • 6.  RE: Continuous Insulation

    Posted 10-16-2019 10:46 PM

    My understanding is that the Zip+ system, properly installed on the outside of the studs, works for the lateral stability you're looking for.

    John Downie AIA
    John V. Downie | Architect
    Auburndale MA

  • 7.  RE: Continuous Insulation

    Posted 10-17-2019 09:32 AM
    You will trap the condensation on the interior - regardless of where you place the weather barrier - and create food for mold.

    William T. Eberhard AIA, IIDA, Managing Partner
    Eberhard Architects LLC
    2077 East 4th Street, Second Floor
    Cleveland, OH 44115
    v: 216.452.4592
    f: 216.737.9999
    c: 216.513.1300

  • 8.  RE: Continuous Insulation

    Posted 10-18-2019 05:32 PM



    I would recommend against this type of install.  Let the framers frame as normal, apply your WRB directly to the sheathing, then install the CI – many years / projects of successful installs.  Best practice would be a rainscreen installation with a furring / strapping over the insulation board, and then install the exterior wall cladding over the strapping. 



    Scott L Witt, AIA CPHC

    Witt Architecture Office

    713 West Johanna St

    Austin, TX  78704





  • 9.  RE: Continuous Insulation

    Posted 10-19-2019 11:36 AM

    You may care to check out Joe Lstiburek/Building Science Corporation's article on "The Perfect Wall".

    The article has very interesting recommendations for wall assemblies with continuous insulation that work in all climate regions.  Also, here's a link to some videos on YouTube of a builder discussing these wall assemblies.


    To your stratospheric success,


    Kendal W. Perkins

    Architect, AIA, MBA


    Apex Architectural Services, LLC

    177 Shamard Drive / Natchitoches, LA  71457

    Tel: (318) 581-3237


    Isn't GOD Good?


  • 10.  RE: Continuous Insulation

    Posted 10-21-2019 05:58 PM

    Regarding the Building Science Corp. people, it's good to know they base most of their expertise on Canadian Building Digests (which were also used to create the american standards - by an ex-professor). That noted with a weather eye they can be adapted to a larger set of weather zones. The big issue is air tightness, with vapour tightness lower on the list, also an understanding of driving elements that will move water where you do not want it. I started practicing in Canada and reading the Canadian Building Digests - produced by the National Research Council. This was the backbone to BSC's early consulting. Since then I've worked in Bermuda and the Virgin Islands (US and UK) where moderate and hot maritime conditions coupled with partial air conditioning and low delta-T can really drive water vapour in all directions, depending on solar orientation and other factors. With that in mind I've worked details with rainscreen, air barrier continuous insulation (rigid rock-wool being a good hydrophobic insulation) plywood, then stud wall with some void insulation, interior air barrier, interior finish. It is important to keep a positive interior pressure when windows are closed (heating or cooling) and to ensure that any fans (exhaust from wc or kitchen) are compensated for to maintain the positive pressure. There are some good products (read $$) coming out of Switzerland with one way vapour flow. Otherwise use careful detailing (eagle eye on Electrical and Mechanical) to prevent any air leaks, and a product with 20 perms or so. On specific projects with specific climate conditions BSC comes into their own for auditing details. The project I did on St. Croix survived Irma and Maria with no visible damage, located 50 feet from the water.

    Christopher Blood AIA
    Sr. Designer
    Ottawa ON