Committee on the Environment

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  • 1.  Energy modeling for small commercial projects

    Posted 02-17-2014 05:31 PM
    We do primarily small office buildings and want to use open cell spray foam insulation on a wood-framed project.  Comcheck will not give us credit for the air barrier provided by the foam, so we are looking for a different way to establish compliance with the 2012 IECC.  Any suggestions?

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    Jane Kittner AIA
    Owner
    Kittner & Pate Design Associates
    Waco TX
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    AIA26 San Diego June 10-13


  • 2.  RE:Energy modeling for small commercial projects

    Posted 02-19-2014 11:09 AM
    It is my understanding that open-cell foam provides no air barrier.  For that you need a heavier closed-cell foam.  Look at buildingscience.com for some information on this.

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    William Downing AIA
    Rohrbach Associates P.C.
    Iowa City IA
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    AIA26 San Diego June 10-13


  • 3.  RE:Energy modeling for small commercial projects

    Posted 02-20-2014 06:09 PM
    William, that is a common misconception.  Open cell foam is classified as an air barrier by the 2012 IECC in C402.4.1.2.1.6 and also on the buildingscience.com website.

    Both closed cell and open cell foam provide an air barrier, but open cell is more vapor permeable, which is really important in our warm/ humid climate (zone 2A).  Our outside conditions in winter can be more humid than the inside air, which leads to interesting condensation in wall and roof assemblies if a vapor barrier or retarder is used.  

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    Jane Kittner AIA
    Owner
    Kittner & Pate Design Associates
    Waco TX
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    Original Message
    AIA26 San Diego June 10-13


  • 4.  RE:Energy modeling for small commercial projects

    Posted 02-22-2014 09:16 AM
    From IECC 2012.  See items 5 and 6.  There are 15, but I only copied up to item 6.  

    C402.4.1.2.1 Materials. Materials with an air permeability

    no greater than 0.004 cfm/ft2 (0.02 L/s · m2)

    under a pressure differential of 0.3 inches water

    gauge (w.g.) (75 Pa) when tested in accordance with

    ASTM E 2178 shall comply with this section. Materials

    in Items 1 through 15 shall be deemed to comply

    with this section provided joints are sealed and

    materials are installed as air barriers in accordance

    with the manufacturer's instructions.

    1. Plywood with a thickness of not less than 3/8

    inch (10 mm).

    2. Oriented strand board having a thickness of

    not less than 3/8 inch (10 mm).

    3. Extruded polystyrene insulation board having

    a thickness of not less than 1/2 inch (12

    mm).

    4. Foil-back polyisocyanurate insulation board

    having a thickness of not less than 1/2 inch

    (12 mm).

    5. Closed cell spray foam a minimum density

    of 1.5 pcf (2.4 kg/m3) having a thickness of

    not less than 11/2 inches (36 mm).

    6. Open cell spray foam with a density

    between 0.4 and 1.5 pcf (0.6 and 2.4 kg/m3)

    and having a thickness of not less than 4.5

    inches (113 mm).


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    James Kirby AIA
    VP of Sustainability
    Center for Environmental Innovation in Roofing
    Evanston IL
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    Original Message
    AIA26 San Diego June 10-13


  • 5.  RE:Energy modeling for small commercial projects

    Posted 02-22-2014 10:56 AM
    Jane,

    I'm not sure exactly how you are using the spray foam insulation on the building, without seeing a wall section it is difficult to understand how you are using this material. If you are applying it in-between the studs it would seem that you are using it as a thermal barrier. The air and vapor barrier would then be applied to the outside of the building on the exterior sheathing with a building wrap. I usually use a closed cell spray foam on the outside of the building so that it becomes an air/vapor/thermal barrier. Then apply the rainscreen to the outside of that. This is usually on CMU construction so not sure how it works with wood frame construction. It also satisfies the continued insulation requirement for the energy code. 

    All of this is region specific of coarse. 

    As far as energy modeling. If you are not reaching your code minimum with ComCheck you might try looking at Green Building Studio or eQuest to get more detail into your energy analysis. 

    Hop this helps. 

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    Roland Mueller AIA
    Project Architect
    RossTarrant Architects, Inc.
    Lexington KY
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    Original Message
    AIA26 San Diego June 10-13


  • 6.  RE:Energy modeling for small commercial projects

    Posted 02-23-2014 06:46 PM
    Since air barriers are not mandatory in zone 2a, it seems logical that Comchek would not show a credit. I am curious how the energy modeling software handles non-mandatory air barriers.  Would this be different depending on the location of the air barrier and the configuration of the building envelope?  It seems likely that a building with a lot of perimeter walls, possibly an attic, a crawl space, or a basement would benefit most from properly located vapor permeable air barriers. Does ASHRAE 90.1 provide any guidance on modeling air barriers?

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    Ellen Berky AIA, LEED AP, CCS
    San Antonio TX
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    Original Message
    AIA26 San Diego June 10-13