Building and Energy Codes

In a Nutshell

The International Energy Conservation Code (IECC) is a standard that, when adopted into law, requires all building types undergoing construction and alteration to be built in such a way that they do not waste energy used for heating, cooling, and lighting. At the same time these construction practices provide more comfortable, less drafty buildings that reduce energy use and energy bills.

Practical Solution

The “How To”The “How To”

Municipalities adopt the IECC into law by the same process that they would adopt any other building code, i.e., (International Building Code which governs commercial construction) IBC and the IRC (International Residential Code for Residential Construction). For resources associated with adoption of the IECC see Energy Codes Adoption Policies.

Currently St. Louis City and County have adopted the 2009 IECC. Other municipalities that use this code include Clayton, Florissant, Hazelwood, Lake St. Louis, O'Fallon, St. Charles, Troy, Wentzville. The entire state of Illinois currently enforces compliance with the 2012 IECC, which produces energy savings of approximately 15% over the 2009 IECC.

Copies of the 2009 or 2012 IECC can be purchased at the International Code Council for $40 each. The Illinois amendments to the 2012 IECC can be found at Illinois Department of Commerce and Economic Opportunity-Energy and Recycling.

Planning & ZoningPlanning & Zoning

Typically, the Department of Building and Safety for each municipality enforces the IECC. Since it is written by the ICC which writes all the other building codes, it is easy for building officials to understand and enforce. The Department of Energy has developed an easy software tool to help builders and designers determine whether a project meets the IECC. This software (REScheck and COMcheck) are free and available on their website and This software allows specific variables to be inputted for a project to see if a project complies making the job of building officials, plan checkers, and inspectors reviews easier.

St. Louis County reviews drawings for code (2009 I-Codes) compliance for some 90 Missouri municipalities in the St. Louis Metro area, making it easier for municipalities in St. Louis County to adopt 2009 IECC.

The Kansas City metro area is on a different code cycle and has adopted the 2012 I-Codes including the 2012 IECC.

Dollars & CentsDollars & Cents

There should be little cost to a municipality or government entity that adopts IECC if they already have a structure in place for compliance.

Detailed return on investments for NEW residential projects built in our climate zone under the 2009 and 2012 IECC have been calculated by the U.S. Department of Energy. These models calculate only the increase in cost between specific materials that would be supplied whether the energy code was in place or not, i.e., R-13 versus R-20 fiberglass insulation. They have taken these specific material cost increases and calculated the increase to a standard monthly mortgage payment (typically attained for new homes). The increase to the mortgage payment was compared to the monthly energy cost increase without these upgrades. Homeowners building new homes would break even at 13 months and start saving $27 per month in energy costs from that point on. Click here to view this documentation.

The same cost saving analysis for NEW residential projects in the St. Louis metro area was also calculated by the Department of Energy. Here is a documentation for cost saving analysis.

The break even point would be 14 months and a $22 cost savings each month from there. Determining the cost savings for residential renovations is much more complicated and needs to be done on a case by case basis since the scope of renovation can vary significantly. For example, kitchen remodels may actually increase energy consumption if appliances are added, going from a range to a cook top and double oven. However, adding insulation and weatherstripping to an existing house has a much quicker return on investment.

Predicting return on investment for commercial projects under the IECC is also much more difficult to calculate, since there are so many variables.

Measuring SuccessMeasuring Success

Adoption of the IECC will reduce energy use, thus creating a savings in energy bills (Electric, Gas, Water) for homeowners, while also providing a more comfortable and healthy building in which to live. Illinois cost payback for new residential construction in our climate zone (4) can be seen and downloaded here at 2012 IECC Incremental Cost Payback.

Missouri cost payback for new residential construction in our climate zone (4) can be seen and downloaded. Click here to view the Missouri Cost Payback for New Residential Construction.

Case StudiesCase Studies

City of Clayton

  • Contact

    Susan Istenes
    AICP, Director of Planning and Development Services
    This email address is being protected from spambots. You need JavaScript enabled to view it.


    10 N. Bemiston - Clayton, MO 63105


    The codes on the City of Clayton’s website are for reference only.  The City encourages sustainable and green building design but doesn’t require it.  You can look up the codes on line and get a brief description of and what they are intended to achieve.

    The City of Clayton, Missouri’s Electrical Codes can be found under Section 500 (Building Codes and Building Regulations)within their Municipal Code. The section reads:


    A.     The Saint Louis County Electrical Code as amended by the County of Saint Louis, Missouri, through date of the last amendatory ordinances, to wit:  County Ordinance 24,439 approved on July 14, 2010, is hereby adopted as the Electrical Code of the City of Clayton, Missouri, as if fully set out herein, with the exception of the first (1st) paragraph of Section 80-17(C) regarding the penalty for violation.”

    The St. Louis County Codes that the Clayton code refers to the St. Louis County Code of Ordinances, Chapter 1102, which lays out the rules for everything from regulation to permitting. St. Louis County uses the National Electric Code.

    The City of Clayton does include environmental goals on page 5 of their “Vision 2013”statement. Guiding principal #III states that, “Clayton resolves to be a leader in environmental initiatives. The goal is to incorporate sustainability in daily operations without increasing costs and to incentivize best practices, such as LEED certification and green roofs, by developers of new and existing buildings. We also recognize the importance of expanding the citywide recycling program to further reduce the amount of refuse transferred into local landfills”.


    The best way to find out this information is to talk to individual developers, builders or architects who have worked on new buildings in Clayton.  Every project is different and the costs associated with green building can be offset by savings over time depending on what systems, construction materials, or methods are used. Susan believes the City has rebuilt only one LEED Certified (Silver she believes) structure.

    Lessons Learned

    Obviously if the City required LEED certified buildings or provided more incentives for conservation, our support and desire for sustainable practices would be more effective, but for now, the City encourages green/sustainable construction and does not require it.

City of O'Fallon IECC

  • Contact

    Chad Cornwell
    This email address is being protected from spambots. You need JavaScript enabled to view it.


    100 North Main Street - O'Fallon, MO 63366


    The City of O'Fallon City Council adopted the ICC building codes which includes the 2009 IECC on 2-10-11. The adopting ordinances from the city of O’Fallon’s can be viewed on their web page in the Building and Permits page. There you will be able to view the adopting ordinance and the changes made to the code during adoption.

    Any time the city gets an application for a new residential or commercial building inspectors are sent out to check for appliances.


    There are no additional costs for the program itself. It is included in the inspection fees and may be on a fee for new residential homes. The inspectors themselves are paid through tax dollars.

    Lessons Learned

    Lessons learned from the implementation of the 2009 IECC include codes becoming more aware of the importance of energy conservation and the long term effects that structures have on energy usage. The codes are requiring better, more energy efficient structures to be constructed. There has not been any pros or cons other than educating the inspectors as well as the contractors on the requirements of the 2009 IECC. This is normal with any new code adoption.

Discover MoreDiscover More

The actual IgCC Code is available for purchase in addition to workbooks and interpretive manuals explaining the codes. The code itself, while lengthy, is fairly readable and explanitory with a lot of helpful information on how to best implement requirements within the code. View more about the IgCC.

Missouri does not have a mandatory statewide energy code; however, all local jurisdictions except class III counties have the right to adopt an energy code. Learn about what policies are being implemented by the Missouri Department of Natural Resources in Saint Louis County and within the City of Saint Louis.