Here is an older email I had recieved.
Next, the Code [2009 IECC] considers window replacements alterations to the building. Yet for some time, many Illinois municipalities had considered the replacement window issue a matter of jurisdictional choice by way of a jurisdiction’s unique adopting ordinance; most often reading, “If it fits into the same opening, then you do not need to obtain a building permit. Where the new window size is different than the size of the opening, a permit application is required.”
With the onset of energy efficiency requirements for residential buildings effective January 29, 2010, all window replacements, as alterations, require a permit in accordance with the Code [2009 IECC]. Jurisdictions subject to the Energy Efficient Building Act will use the 2009 IECC to perform compliance assessment for both residential buildings, and thereby to inspect and verify fenestration thermal performance (U-factor, Solar Heat Gain Coefficient and Air leakage) for homeowners in their communities. This will take some extra public relations and communications to get the word out for the new permit requirement; a perfect opportunity for Building Safety Month.
Section 600.110, Part c) 2) of the Act, entitled Privately Funded Commercial Facilities and Residential Buildings, reads:
“The Code as [2009 IECC] described in Subparts C [Privately Funded Commercial Facilities] and D [Residential Building] of this Part applies to any new building or structure in this State for which a building permit application is received by a municipality or county. [20 ILCS 3125/20]
A) Additions, alterations, renovations or repairs to an existing building, building system or portion thereof shall conform to the provisions of the Code [2009 IECC] as they relate to new construction without requiring the unaltered portion of the existing building or building system to comply with the Code [2009 IECC]. [20 ILCS 3125/20©]
B) All exceptions listed in the Code [2009 IECC] related to additions, alterations, renovations or repairs to an existing building are acceptable provided the energy use of the building is not increased.
[underline emphasis intended]