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Residential Energy Conservation Code

​On March 7, 2017, the city adopted a new energy code, the 2017 City of Boulder Energy Conservation Code (COBECC), which is based on the International Energy Conservation Code (IECC) 2012, with local amendments to the International Building Code (IBC), International Plumbing Code (IPC) and International Residential Code (IRC) to address energy and sustainability issues. The effective date for all new projects will be May 8, 2017.  Projects submitting building permit applications on or after May 8, 2017 are subject to the 2017 COBECC.

Please refer to the links provided on the sidebar for an Amendment Summary, Mandatory Measures Checklist, and Prescriptive Measures Checklist. The applicable checklist(s) shall be completed and included on an "Energy Conservation Code" sheet within the plans being submitted for permit.

The most significant changes to the residential construction requirements are:

  • restructuring and updating the existing residential energy code, Green Building and Green Points, which is now within the new COBECC and amendments into the IRC.
  • new process for calculating an Energy Rating Index (ERI, same as HERS) requirement for additions
  •  > 5,000 sq. ft. houses are required to be Net Zero Energy (NZE)
  • revisions to Title 9, incorporating single family residential landscaping requirements
  • electric vehicle charging infrastructure and solar-ready requirements for the installation of future photovoltaic systems.
  • allowing off-site renewable energy for residential energy code compliance.
  • addition of new radon mitigation requirements   

2017 Energy Code Changes

  • The 2017 COBECC is based off the previously adopted 2012 International Energy Conservation Code (IECC) and Green Building Green Points Program. It provides a single source for all of Boulder's energy code requirements. Previously, users would have to reference the 2012 IECC and review applicable amendments in the Boulder Revised Code. With the introduction of the 2017 COBECC, all of Boulder’s energy codes are detailed in a single source. 
  • Multifamily buildings are treated differently under the 2017 COBECC. Residential buildings only include single family homes, townhomes, duplexes and R-3 and R-4 occupancy buildings (includes boarding and care facilities). Any mixed use or multifamily apartment or condo buildings will be regulated under the commercial code.
  • The Green Building Green Points Program is no longer required as sustainability measures such as landscaping, electrical vehicle charging and solar ready standards have been incorporated into the COBECC and the Boulder Revised Code. To locate and learn more about additional sustainability measures not found in the COBECC, please refer to the Residential Amendment Summary pdf.
  • Energy Rating Index (ERI) requirements for residential new construction, alterations and additions have been updated. 

New Construction and Energy Rating Index (ERI) Calculator

New residential construction projects (less than) < 500 sq. ft. shall comply with the residential energy efficiency mandatory and prescriptive requirements in the City of Boulder Energy Conservation Code (COBECC). Projects greater than or equal to 500 sq. ft. shall comply with the mandatory requirements and are required to achieve the applicable Energy Rating Index (ERI) . The ERI is the non-trademark equivalent to a HERS score used in energy codes and provides an energy efficiency requirement for your residential construction project. New residential construction is moving toward Net Zero Energy, with all buildings being required to meet that standard by 2031.

The larger the house, the lower the ERI (increased efficiency). Houses larger than 5,000 sq. ft. are now required to be NZE.  Further explanation can be referenced in the COBECC, Section R401.2.1.

INSTRUCTIONS : Follow the 2 steps below to calculate your ERI requirement for your project. The calculator estimates your ERI requirement based on your total proposed home size.

Required fields

Step/Calculation Total

Step 1. Input Proposed Home Size

Step 2: Record your ERI

To search for local certified RESENT home energy raters that can calculate your project's ERI click  here.

Additions and Energy Rating Index (ERI) Calculator

Residential construction projects adding (less than) < 1,000 sq. ft. of floor area to an existing house shall comply with the residential energy efficiency mandatory and prescriptive requirements in the City of Boulder Energy Conservation Code (COBECC). Additions (greater than) > 1,000 sq. ft. of floor area shall comply with the mandatory requirements and are required to achieve the applicable Energy Rating Index (ERI) .

The ERI is the non-trademark equivalent to a HERS score used in the energy codes and provides an energy efficiency requirement for your residential construction project. Further explanation can be referenced in the city of Boulder Energy Conservation Code (COBECC), Section R401.2.2.

INSTRUCTIONS: Follow the 3 steps below to calculate the ERI requirement for your project. The calculator estimates your ERI requirement based on an estimated total conditioned space and the percent the addition will increase your current square footage. (i.e. addition sqft/proposed total sqft).

Required fields

Step/Calculation Total

Step 1. Input Existing Home Size

Step 2. Input Size of Addition

Calculated: Total Proposed Conditioned Floor Area

Calculated: Addition is % of total square feet

Step 3: Record your ERI

  •  Table R401.2.2.2(3) pdf summarizes the ERI requirements for additions, but is illustrative only as it does not show the applicable ERI for all possible scenarios.
  • The “Existing Home Size” is the square footage of the existing home that will remain (after demolition).

To search for local certified RESENT home energy raters that can calculate your project's ERI click  here.  

Alterations and Repairs

Alterations and repairs to residential buildings shall meet residential energy efficiency mandatory and prescriptive requirements established in the City of Boulder Energy Conservation Code (COBECC) and building code requirements based on the construction value of the project relative to the Actual Value of the existing building per the Boulder County Tax Assessor's database:

  • Construction value < 26% of Assessed Value: Homeowner must contact a qualified energy advisor, as defined by the city manager, and discuss the construction project to learn how efficiency opportunities can be maximized.
  • Construction value 26 - 50% of Assessed Value: Homeowner must contact a qualified energy advisor, as defined by the city manager, receive an energy assessment, and discuss the construction project to learn how efficiency opportunities can be maximized. Additionally, air sealing and insulation in ceiling and walls are required when applicable to meet code. Crawl space insulation, vapor barrier, and ventilation portions shall also meet the requirements of the COBECC.
  • Construction value > 50% of Assessed Value: Triggers new construction ERI requirements.

  Further explanation can be referenced in the COBECC, Section R401.2.3.

Documenting Energy Code Compliance

Checklists have been created to improve compliance and enforcement processes. Based on a project’s energy code compliance path, corresponding documentation will be required with permit application. Refer to the diagram below to confirm your projects compliance path. 

Compliance Path

Per the diagram above, all residential projects must meet the mandatory residential provisions in the 2017 COBECC.  The corresponding Residential Mandatory Measure Checklist xlsx must be completed and included on an “Energy Conservation Code” sheet within the plans being submitted.  Depending on square footage and/or construction value, projects will either need to comply with the prescriptive requirements or demonstrate target ERIs have been achieved.  A Residential Prescriptive Measure Checklist xlsx has been developed and, where applicable, shall be completed and included on the “Energy Conservation Code” sheet.  Projects required to meet ERI targets shall submit an ERI Compliance Report generated by the compliance software tool.  The report shall include: ERI certificate, project address, projected annual site energy use by fuel type, projected annual energy cost, name and address of the approved rating provider, date of the home energy rating, the name and version of the compliance software tool, and an inspection checklist.  The inspection checklist shall show results for both the ERI reference design and the rated design, and shall document all inputs entered by the user necessary to reproduce the results. The ERI Compliance Report shall be submitted with the permit application. 

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