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

Scope

Identify what materials will constitute the continuous air barrier around the building envelope.
Identify what materials will constitute the continuous air barrier around the building envelope.

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.

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

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).

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.

Climate

Climate-specific requirements as specified in the IECC are shown in Table 1 on the Compliance Tab of this guide. 

IECC climate zone map
IECC Climate Zone Map

 

Training

Right and Wrong Images

Presentations

  1. Zero Energy Ready Home Training
    Author(s): Rashkin
    Organization(s): DOE

Videos

  1. 2012 IECC Code Level Insulation – DOE Zero Energy Ready Home Requirements
    Publication Date: July, 2015
    Courtesy Of: Risinger Homes

    Video describing insulation and air sealing strategies to meet 2012 IECC code levels.

CAD Images

None Available

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 Certified Homes (Ver 3/3.1, Rev 09)

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 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.  

200920122015, and 2018 IECC / 200920122015, and 2018 IRC

The minimum insulation requirements for ceilings, walls, floors, and foundations in new homes, as listed in the 2009, 2012, 2015, and 2018 IECC and IRC, can be found in Table 1. 

Minimum Insulation Requirements for New Homes as Listed in the 2009, 2012, 2015, and 2018 IECC and 2009, 2012, 2015, and 2018 IRC.

Retrofit: 2009, 2012, 2015, and 2018 IECC

Section R101.4.3 (Section R501.1.1 in 2015 and 2018 IECC). 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.)

2009 IRC, 2012 IRC, 2015 IRC, and 2018 IRC

For IRC 2009-18 insulation requirements, see Table 1 above. Insulation requirements are described in Chapter 11 Energy Efficiency. Water management details are descried in R405 Foundation Drainage and R406 Foundation Waterproofing and Dampproofing.

Retrofit: 2009, 2012, 2015, and 2018 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018 IRC). 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.)

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

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

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: September, 2013

    Case study of a DOE Zero Energy Ready Home in Herriman, UT, that scored HERS 40 without PV, -1 with PV. This 4,111 ft2 production home has R-23 advanced framed walls, and a vented attic with R-60 blown fiberglass.

  2. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: September, 2013

    Case study of a DOE Zero Energy Ready Home in Downers Grove IL that scored HERS 35 without PV. This 3,600 ft2 custom home has advanced framed walls with R-23 dense-packed fiberglass plus R-13 rigid polyiso, a sealed attic with open-cell spray foam, a pier foundation, and 95% efficient gas furnace.

References and Resources*

  1. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2012

    Code establishing a baseline for energy efficiency by setting performance standards for the building envelope (defined as the boundary that separates heated/cooled air from unconditioned, outside air), mechanical systems, lighting systems and service water heating systems in homes and commercial businesses.

  2. Author(s): Baechler, Adams, Hefty, Gilbride, Love
    Organization(s): Pacific Northwest National Laboratory, Oak Ridge National Laboratory
    Publication Date: May, 2012

    Guide to help contractors and homeowners identify ways to make homes more comfortable, more energy efficient, and healthier to live in.

  3. Author(s): U.S. Department of Energy
    Organization(s): DOE
    Publication Date: May, 2019

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  4. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: June, 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

Last Updated: 07/16/2019