This is part 2 of a 2 part article regarding the updates to the IRC and IECC code requirements. We strongly advise contractors acquire and refer to their own copy of the IRC and IECC for full code requirements.
International Codes, as published by the International Code Council, are the most widely used codes in construction within the United States. They have also been adopted by many federal agencies, such as the National Park Service and the Department of Defense which has led to the codes being enforced in foreign countries as well.
Design load provisions of all exteriors of residential structures – including fenestration, can be found in the 2018 IRC R301.
Wind Loads
Tables R301.2(2) and R301.2(3) give the wind load design for glazed openings based on wind speed of the location where construction is to take place, the mean building height and exposure to wind. Overall, the prescriptive provisions of the 2018 IRC remain unchanged from the 2015 IRC and will continue to be based on the 2010 edition of ASCE 7. However, homes that are outside the prescriptive provision scope of the 2018 IRC must be designed using the 2016 edition of the ASCE 7.
It is crucial the builder, code official, manufacturer and anyone else involved in choosing or approving the windows doors and skylights must be aware of which set of provisions is being used to determine the design wind pressures for the home.
Dead Loads
The 2018 IRC Section R301.1 provisions for dead loans are based on ASCE 7-10 with no significant changes between the 2015 and 2018 editions.
Impact Resistance
Section R301.2.1.2 of the 2018 IRC outlines locations where impact-resistant products are required. Homes that fall within the prescriptive provisions of the 2018 IRC for impact protection of openings are similar to those in the ASCE 7-10 and are primarily defined by design wind speed. Those homes that are outside the scope of prescriptive provisions will be determined in accordance with ASCE 7-16.
AAMA 506 certification label tab is also recognized as evidence that a product has been tested appropriately by the 2018 IRC. This provides a method for a window manufacturer to demonstrate the product has been successfully tested in accordance with ASTM E1866 and ASTM E1996.
Energy Performance
The 2018 IECC includes requirements for energy performance in residential and commercial buildings. Energy conservation requirements one- and two-family homes and townhouses three stories in height of less can also be found in Chapter 11 of the 2018 IRC.
Compliance Paths
The prescriptive path of the 2018 IECC for residential construction does not have a limit on the percentage of glazing in the exterior wall, or the percentage of roof area with skylights. The maximum permitted U-factor for vertical glazing was reduced in Climate Zone 4 from 0.35 to 0.35 and Climage Zones 5 to 8 from 0.32 to 0.30.
Exterior Glass Doors
Glass doors, as defined by the IECC, have an area that is more than 50 percent glass; doors with 50 percent or less are considered an opaque door. Opaque doors have a maximum U-factor of 0.35, separate from the vertical fenestration U-factor requirements. One opaque door up to 24 square feet in area is exempt from the maximum U-factor requirement in the 2018 IECC and 2018 IRC.
New ERI Path
In the 2018 IECC, the new Energy Rating Index (ERI) path compares anticipated energy usage of a proposed residence to one built under 2006 IECC. Residences built using the 2018 IECC compliance path are required to not consume more than 51 to 54 percent of the energy used for a similar size home built under the 2006 IECC, based upon residence location.
Air Leakage
Similar to the 2015 IECC and IRC, the 2018 IECC and IRC require air leakage to be determined in accordance with NAFS-17 or NFRC400-14.
Section R308.6.3 includes requirements for screening under skylights and sloped glazing, and are consistent with previous editions, including the requirement that screening be securely fastened and able to support twice the dead weight of the glass.
Note: The above information is a summary of the major requirements recently published in the 2018 I-codes, this is not a full listing of all updated requirements. We advise our customers to always refer to their own copy of the the IRC and IECC for the code(s) relevant to their project.
