Replacement Windows in International Codes

Julie Ruth
August 8, 2015
COLUMN : Code Arena | Codes & Standards

Our discussion this month focuses on the specific requirements for residential replacement windows found in the 2015 International Residential Code, International Energy Conservation Code and International Existing Building Code.

These international codes require any repairs or alterations to an existing building to comply with the requirements of the applicable code for new construction. This includes replacement of an entire window (including sash and frame), or just replacement of glass in an existing frame. For example, if a flying baseball shatters single pane glass in a 1920s bungalow window, as a general rule, whatever goes into that opening must meet the requirements of the applicable code for new construction.

Some of the specific provisions of the 2015 International Codes with regard to replacement windows or glazing are consistent with this philosophy. These include provisions for safety glazing and for Window Opening Control Devices (WOCDs).

The international codes specifically state that safety glazing must be used when replacing glass in an opening that is considered a hazardous location. So, if the glass in the 1920s bungalow is in a door, door sidelite, a large pane of glass, or glazing near stairs, ramps, pools, tubs or showers, it may need to be replaced with safety glazing, even though the original glass was not.

The 2015 IRC and 2015 IEBC also require installation of WOCDs on replacement windows installed in locations where these devices would be required in new construction.

Thus, if the shattered glass in our example is to be replaced by an operable window that opens more than 4 inches, is located 6 feet or more above the exterior grade or plane below the window, and is within 24 inches of the interior floor of the home, that window would need to be equipped with a WOCD. The device limits the initial opening of the window to no more than 4 inches while permitting the window to be opened further upon release of the mechanism. The WOCD must comply with ASTM F2090.

Energy & Emergency Escape

In other instances, specific provisions of the international codes override the more general provisions. For replacement windows, this is true with regard to energy conservation, and emergency escape and rescue openings.

The 2015 versions of IRC and IECC require replacement fenestration to comply with the prescriptive U-factor and SHGC requirements for fenestration in new construction whenever all or part of an existing fenestration unit is replaced. They also state, however, that replacement of glass only in an existing sash and frame is considered a repair. Repairs are not subject to the provisions for new construction.

Therefore, if only the glass is going to be replaced in the 1920s bungalow and no other factors require different glass, it could be replaced with single pane glass. However, if the entire window unit, including sash and frame is to be replaced, it must be replaced with a window unit that meets the prescriptive requirements of the 2015 IECC.

Finally, the 2015 versions of IRC and IEBC have specific provisions for replacement windows that are required to provide EERO. As long as the window replacement is not occurring due to a change in occupancy of the building (i.e. a home is not being converted to a restaurant or retail shop), the replacement may consist of the manufacturer’s largest standard style window of the same operating type as the existing window that will fit into the existing opening.

This is true even if this window does not provide the clear opening size otherwise required for EERO by the IRC (5.0 square feet for windows at or below grade, 5.7 square feet for above-grade windows). An alternate operating style window that provides the same or greater clear opening may also be used. So, in the example of the shattered window in the 1920s bungalow, if the window is located in a sleeping room that would otherwise require an EERO per the 2015 IRC, but the existing wall opening is not large enough to accommodate an EERO of the same operating style as the existing window, the wall does not need to be reframed to provide a larger opening.

Code Arena is brought to you by the America Architectural Manufacturers Association. Julie Ruth may be reached through AAMA at 847/303-5664 or via e-mail at