Consistent Definitions of Fenestration

Julie Ruth
October 17, 2016
COLUMN : Code Arena | Codes & Standards

The series of columns on the more significant proposed changes to the 2015 International Code Council Group B codes and their potential impact on the fenestration industry continues. This month’s column discusses the establishment of consistent definitions of fenestration in the International Residential Code and International Energy Conservation Code that were approved during the 2016 ICC Group B Committee Action Hearings. If the approval of these proposed changes is upheld through the Public Comment Hearings and Final Action Online Voting, they will be included in the 2018 editions of the IRC and the IECC.

Fenestration Definitions

AAMA submitted two proposals (G9 and G10) to provide definitions of “Fenestration,” “Vertical Fenestration” and “Skylights and Sloped Glazing” in the IBC and IRC that are consistent with those in the IECC. The proposals were broken into a total of six parts. Five of these were approved during the ICC Group B CAH. Based upon the CAH action, the definitions of these terms that would appear in the 2018 IRC are as follows.

Fenestration: Products classified as either vertical fenestration or skylights and sloped glazing, installed in such a manner as to preserve the weather resistant barrier of the wall or roof in which they are installed. Fenestration includes products with glass or other transparent or translucent materials.

Fenestration, Vertical: Windows that are fixed or movable, opaque doors, glazed doors, glazed block, and combination opaque and glazed doors installed in a wall at less than 15 degrees from vertical.

Skylights and Sloped Glazing: Glass or other transparent or translucent glazing material installed at a slope of 15 degrees (0.26 rad) or more from vertical. Unit skylights, tubular daylighting devices and glazing materials in solariums, sunrooms, roofs and sloped walls are included in this definition.

These definitions clarify that fenestration consists of both vertical glazing, as well as skylights and sloped glazing, and preserves the weather-resistant barrier of the building envelope component it is placed in. It also clarifies that tubular daylighting devices are to be treated as fenestration and, therefore, must be installed in such a manner as to preserve the weather resistance of the roof in which they are installed. Finally, they establish the angle at which fenestration goes from being vertical to sloped glazing as 15 degrees from vertical.

The definitions proposed for the IECC were similar, but with two distinct differences. First, they do not include the provisions that fenestration preserves the weather-resistant barrier of the building envelope. And second, they establish the angle at which fenestration goes from being sloped glazing to vertical as 60 degrees from horizontal (30 degrees from vertical). The IECC-Residential Committee disapproved the proposed definition for skylights and sloped glazing.

Although there is some concern about a different angle being used to distinguish between vertical glazing and skylights in the IECC versus the IBC, the standards used to measure energy performance of skylights (NFRC 100 and NFRC 200) are based upon an angle of 60 degrees from horizontal. The angle used to distinguish when air, water and structural tests are to be performed on skylights versus vertical glazing in the IBC and IRC, however, has traditionally been based upon 15 degrees from vertical.

Completion of the 2018 Group B I-Codes

Anyone who disagreed with the committee action on any of the ICC Group B proposals was able to challenge it by submitting a Public Comment, which was due July 22. AAMA submitted a PC challenging the IECC-Residential Committee disapproval of the proposed definition of skylights and sloped glazing.

The Public Comments were to be posted on the ICC website in September.

Once posted, several organizations, including AAMA, will review the Public Comments and develop their positions on them. The Public Comments will be heard and voted on during the ICC Group B Public Comment Hearings, scheduled for October 19 through 25 at the Kansas City Convention Center in Kansas City, Missouri.

The results of the Public Comment Hearings will be sent out to the active governmental member voting representatives for online voting in early November. The action taken during the Public Comment Hearings will not be finalized until online voting is complete.

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