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2015 IECC Code Level Insulation – DOE Zero Energy Ready Home Requirements

    Scope
    Scope

    Install ceiling, wall, and foundation insulation that meets or exceeds the requirements of the most recent International Energy Conservation Code adopted by your state or municipality. If you are pursuing ENERGY STAR or DOE Zero Energy Ready Home certification, follow the version and revision requirements relevant to your state. See ENERGY STAR National Program Requirements webpage for a current table of versions required for each U.S. state and territory and adoption dates based on home permit dates.

    See the Compliance Tab for related codes and standards requirements, and specific criteria to meet ENERGY STAR Single-Family New Homes and DOE’s Zero Energy Ready Home program.

    Description
    Description

    The U.S. Department of Energy Zero Energy Ready Home Program specifies that all certified homes should meet the mandatory requirements listed in Exhibit 1 of the DOE Zero Energy Ready Home National Program Requirements. Item 2.2 in the mandatory requirements requires that “ceiling, wall, floor, and slab insulation shall meet or exceed 2015 IECC levels.”

    The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the 2015 IECC can be found on the Compliance Tab of this guide. 

    The DOE Zero Energy Ready Home program includes two paths: the prescriptive path and the performance path.

    How to follow the DOE Zero Energy Ready Home Prescriptive Path for 2015 IECC Insulation Levels

    First determine whether you are eligible to use the prescriptive path, as described in the DOE Zero Energy Ready Home National Program Requirements. Eligibility is based on the number of bedrooms and overall square footage of the home; larger homes typically must use the performance path.  If you are eligible to use the prescriptive requirements and choose to use this method, construct your home following the mandatory requirements of Exhibit 1 as well as the requirements of Exhibit 2. Both lists stipulate that insulation levels should meet or exceed 2015 IECC levels as listed in Table R402.1.1, with the following notes and exceptions:

    1. Steel-frame ceilings, walls, and floors shall meet the insulation requirements of the 2015 IECC – Table 402.2.6.
    2. For ceilings with attic spaces, R-30 shall satisfy the requirement for R-38 and R-38 shall satisfy the requirement for R-49 wherever the full height of uncompressed insulation at the lower R-value extends over the wall top plate at the eaves. This exemption shall not apply if the alternative calculations in d) are used;
    3. For ceilings without attic spaces, R-30 shall satisfy the requirement for any required value above R-30 if the design of the roof / ceiling assembly does not provide sufficient space for the required insulation value. This exemption shall be limited to 500 sq. ft. or 20% of the total insulated ceiling area, whichever is less. This exemption shall not apply if the alternative calculations in d) are used;
    4. An alternative equivalent U-factor or total UA calculation may also be used to demonstrate compliance, as follows: An assembly with a U-factor equal to or less than specified in 2015 IECC Table 402.1.3 complies. A total building thermal envelope UA that is less than or equal to the total UA resulting from the U-factors in Table 402.1.3 also complies. The insulation levels of fenestration, ceilings, walls, floors, and slabs can be traded off using the UA approach under both the Prescriptive and the Performance Path. Also, note that while ceiling and slab insulation can be included in trade-off calculations, Items 4.1 through 4.3 of the ENERGY STAR for Homes V3 Thermal Enclosure System Rater Checklist shall be met regardless of the UA tradeoffs calculated. The UA calculation shall be done using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials. The calculation for a steel-frame envelope assembly shall use the ASHRAE zone method or a method providing equivalent results, and not a series-parallel path calculation method.

    How to follow the DOE Zero Energy Ready Home Performance Path for 2015 IECC Insulation Levels

    Builders following the Zero Energy Ready Home performance path must meet all of the mandatory requirements in Exhibit 1 and must also meet or exceed the overall HERS Index score generated for their home by modeling software, as defined by Exhibit 2. To determine a target HERS index, the home, as designed, is modeled using the requirements listed in Exhibit 1 and 2. The software creates a target HERS index based on the climate, HVAC, and water heating equipment selected, and other specifics about the home. 

    Exhibit 2 sets insulation target levels and requires builders to meet the 2015 IECC and achieve Grade 1 installation, per RESNET standards.  For more on RESNET Grade 1 insulation installation, see Insulation Installation (RESNET Grade 1).

    Success
    Ensuring Success

    Insulation installation should be inspected by site supervisors before drywall is installed to confirm that specified amounts of insulation have been installed and that installation meets RESNET Grade 1 standards. It is important to consult the insulation requirements of the 2015 International Energy Conservation Code (IECC) to ensure the R-value (or U-value) requirements are met or exceeded. A table of these R-value requirements is provided in the Compliance Tab.  Be sure to review the exceptions listed for ceilings as these can affect the required insulation levels.

    Typical R-values for common insulation materials are summarized in this table, which also identifies the vapor retarder classification for each insulation.

    Climate
    Climate

    The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) 2009, 2012, 2015, and 2018. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC 2021. Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide.

    Climate Zone Map from IECC 2009, 12, 15, and 18.
    Figure 1. Climate Zone Map from IECC 2009, 12, 15, and 18 (Source: 2012 IECC).

     

    Climate Zone Map from IECC 2021.
    Figure 2. Climate Zone Map from IECC 2021 (Source: 2021 IECC).

     

    Training
    Right and Wrong Images
    Image
    Wrong – Insulation has misalignment, compression, and gaps
    Wrong – Insulation has misalignment, compression, and gaps
    Image
    Right – RESNET grade I installation of batt insulation
    Right – RESNET grade I installation of batt insulation
    Image
    Wrong – Compression and misalignment because insulation is not split around wires
    Wrong – Compression and misalignment because insulation is not split around wires
    Image
    Right - Batt was properly split around wires to achieve RESNET Grade I
    Right - Batt was properly split around wires to achieve RESNET Grade I
    Image
    Wrong – Compression and misalignment because insulation is not split around plumbing
    Wrong – Compression and misalignment because insulation is not split around plumbing
    Image
    Right – RESNET Grade I installation of blown insulation
    Right – RESNET Grade I installation of blown insulation
    Image
    Wrong – Spray foam installed with voids
    Wrong – Spray foam installed with voids
    Image
    RESNET Grade I installation of spray foam insulation
    RESNET Grade I installation of spray foam insulation
    Image
    Larsen trusses made of 9-inch I joists, set perpendicular to the exterior wall at 16 inches on center, provide a second wall cavity that can be filled with blown insulation, greatly increasing the insulation value in the walls.
    Larsen trusses made of 9-inch I joists, set perpendicular to the exterior wall at 16 inches on center, provide a second wall cavity that can be filled with blown insulation, greatly increasing the insulation value in the walls.
    Presentations
    Author(s)
    Alea German
    Organization(s)
    Frontier Energy
    Publication Date
    Description
    Webinar that reviews what zero energy or zero net energy homes are and how they are designed and used at a high level.
    Videos
    Compliance

    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    ENERGY STAR Single-Family New Homes (Ver 3/3.1, Rev 11)

    ENERGY STAR for Homes requires that ceiling, wall, floor, and slab insulation levels meet or exceed those specified in the 2009 International Energy Conservation Code (IECC), if following ENERGY STAR Certified Homes Version 3.0. See the guide 2009 and 2012 IECC Code Level Insulation – ENERGY STAR Requirements for more information. States that have adopted IECC 2012, 2015, or 2018 must meet the requirements of ENERGY STAR Version 3.1, which specifies that homes meet or exceed 2012 IECC insulation levels. Regional program requirements, and associated implementation timelines, have been developed for homes in CA, FL, GU, HI, the Northern Mariana Islands, OR, PR, and WA. The National Version 3.1 and regional program requirements can be found at ENERGY STAR's Residential New Construction Program Requirements web page.

     

    DOE Zero Energy Ready Home (ZERH) Revision 07

    Exhibit 1 Mandatory Requirements.
    Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
    Exhibit 2, Item 2) Ceiling, wall, floor, and slab insulation shall meet or exceed 2015 IECC levels and achieve Grade 1 installation, per RESNET standards.

    Footnote 12) Building envelope assemblies, including exterior walls and unvented attic assemblies (where used), shall comply with the relevant vapor retarder provisions of the 2015 International Residential Code (IRC).

    Footnote 13) Insulation levels in a home shall meet or exceed the component insulation requirements in the 2015 International Energy Conservation Code (IECC) - Table R402.1.2. The following notes and exceptions apply:

    1. Steel-frame ceilings, walls, and floors shall meet the insulation requirements of the 2015 IECC – Table 402.2.6.
    2. For ceilings with attic spaces, R-30 shall satisfy the requirement for R-38 and R-38 shall satisfy the requirement for R-49 wherever the full height of uncompressed insulation at the lower R-value extends over the wall top plate at the eaves. This exemption shall not apply if the alternative calculations in d) are used;
    3. For ceilings without attic spaces, R-30 shall satisfy the requirement for any required value above R-30 if the design of the roof / ceiling assembly does not provide sufficient space for the required insulation value. This exemption shall be limited to 500 sq. ft. or 20% of the total insulated ceiling area, whichever is less. This exemption shall not apply if the alternative calculations in d) are used;
    4. An alternative equivalent U-factor or total UA calculation may also be used to demonstrate compliance, as follows: An assembly with a U-factor equal or less than specified in 2015 IECC Table 402.1.4 complies. A total building thermal envelope UA that is less than or equal to the total UA resulting from the U-factors in Table 402.1.4 also complies. The insulation levels of fenestration, ceilings, walls, floors, and slabs can be traded off using the UA approach under both the Prescriptive and the Performance Path. Also, note that while ceiling and slab insulation can be included in trade-off calculations, Items 3.1 through 3.3 of the ENERGY STAR for Homes Rev 09 Rater Field Checklist shall be met regardless of the UA tradeoffs calculated. The UA calculation shall be done using a method consistent with the ASHRAE Handbook of Fundamentals and shall include the thermal bridging effects of framing materials. The calculation for a steel-frame envelope assembly shall use the ASHRAE zone method or a method providing equivalent results, and not a series-parallel path calculation method.

    Builders following the Zero Energy Ready Home performance path must determine a target HERS score by modelling their designed home.  The home must meet the mandatory requirements shown in Exhibit 1 of the DOE Zero Energy Ready Home National Program Requirements as well as the overall target HERS index as defined by Exhibit 2.

    Exhibit 2 sets the insulation target at the 2015 IECC and requires Grade 1 installation, per RESNET standards.  

     

    2009-2021 IECC and IRC Insulation Requirements Table

    The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the 2009, 2012, 2015, 2018, and 2021 IECC and IRC, can be found in this table

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IECC

    Section R101.4.3 (in 2009 and 2012). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

    Chapter 5 (in 2015, 2018, 2021). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    More

    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    Case Studies
    Author(s)
    Pacific Northwest National Laboratory,
    U.S. Department of Energy
    Organization(s)
    PNNL,
    DOE
    Publication Date
    Description
    Case study describing a DOE Zero Energy Ready Home 2013 Housing Innovation Award Winner in Herriman, UT, that scored HERS 40 without PV, -1 with PV.
    References and Resources*
    Author(s)
    Baechler Michael C,
    Adams Karen T,
    Hefty Marye G,
    Gilbride Theresa L,
    Love Pat M
    Organization(s)
    Pacific Northwest National Laboratory,
    PNNL,
    Oak Ridge National Laboratory,
    ORNL,
    U.S. Department of Energy,
    DOE
    Publication Date
    Description
    Document providing descriptions of the many insulation options available to homeowners, along with guidance on where, when, and how to install insulation throughout your house.
    Author(s)
    ENERGY STAR
    Organization(s)
    ENERGY STAR
    Publication Date
    Description
    Website showing compliance timelines for various versions of the ENERGY STAR Single-Family New Home program requirements with links to national program requirements documents and checklists.
    *For non-dated media, such as websites, the date listed is the date accessed.
    Sales
    Building Science Measures
    Building Science-to-Sales Translator

    High-R Insulation = High-Efficiency or Ultra-Efficient Insulation

    Image(s)
    Technical Description

    There are two levels of insulation: high-efficiency insulation, which meets the 2015 International Energy Conservation Code, and ultra-efficient insulation, which is 25% more efficient than this national code. Using high-efficiency and ultra-efficient insulation along with professional installation (e.g., no gaps, voids, compression, or misalignment with air barriers; complete air barriers; and minimal thermal bridging) creates conditioned spaces that require very little heating and cooling, along with, even comfort and quiet throughout the house.

    High-Efficiency or Ultra-Efficient Insulation
    Sales Message

    High-efficiency insulation helps provide added thermal protection. What this means to you is less wasted energy along with enhanced comfort and quiet. Knowing there is only one opportunity during construction to lock in your home’s thermal protection, wouldn’t you agree high-efficiency insulation that meets or exceeds future codes is a great investment?

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