Code Update Presented During Fall WebinarDecember 21, 2011
On November 15, the AAMA Western Region sponsored a Fall Webinar, featuring two speakers discussing code requirements and green attributes. AAMA’s code consultant, Julie Ruth, PE, provided an overview of the status of I-code referencing by Western Region states, as well as an overview of code requirements affecting windows, doors and skylights. Consultant George Middleton then provided some valuable tips on reaching architects and specifiers regarding the green characteristics of fenestration products.
I-Code Summary for Western Region States
The table below indicates those I-codes that Western Region states have adopted:
The 2009 International Energy Conservation Code (IECC) covers both residential and commercial construction. Residential U-factor and solar heat gain coefficient (SHGC) can be prescriptive or performance-based, with tradeoffs accepted excluding those involving high-efficiency HVAC systems. Commercial construction allows compliance with the IECC or ASHRAE 90.1, with HVAC tradeoffs allowed.
The 2012 IECC ratchets up the prescriptive requirements as the following table illustrates (changed requirements highlighted):
Other fenestration-related code provisions were summarized as follows:
The 2009 IBC references ASCE 7-05 for determining design wind loads (snow loads for skylights). It is based on the “allowable stress” design approach, intended to maintain serviceability of the structure. Glass selection is based on ASTM E1300-04e01, which assumes the glass is firmly supported on all four sides by members (of length L) limited in deflection to L/175. If not so supported, the glass must be evaluated by a professional engineer.
In the 2012 IBC, the 2010 version of ASCE 7 is referenced. It includes three separate wind speed maps based on risk category and frequency of recurrence (return period) of the maximum wind speed. Category I, low hazard to humans, such as agricultural or storage buildings and a frequency of recurrence of the maximum wind speed of 300 years, which translates to a 0.33% probability each year; Category II, moderate hazard, with a 700 year recurrence (0.14% annual probability) and Categories III and IV (severe hazard and essential facilities) with a 1700 year return period (0.06% annual probability). ASCE 7-10 is based on the strength design approach, which is intended to avoid structure failure. The proper use of adjustment factors, however, makes the impact of the changed design approach negligible in terms of Design Pressure for most fenestration.
For more details about the application of ASCE 7-10, see the AAMA Wind Loads Technical Bulletin.
Air, Water and Structural Performance
The 2009 and 2012 IRC and IBC reference NAFS-08 and require a compliance labeling program with third-party inspection.
The 2009 IBC and IRC are required when coastal wind speeds exceed 120 mph, or 110 mph within a mile of the shoreline. This applies on a statewide basis to Hawaii due to the fact that all of the land within the islands is near coastlines.
Minimum Sill Height and Opening Limits
The 2009 IBC and IRC specify a minimum sill height of 24 inches where the sill is more than six feet above an exterior surface. This is waived if the window is equipped with guards (meeting ASTM F2090 and/or ASTM F2006) or (in the IRC) with a “window opening limiting device” (WOLD) that prevents an opening greater than four inches. The 2012 IBC changes the minimum sill height to 36 inches, but remains the same otherwise.
Urban-Wildland Interface Code
The IUWIC requires insulating glass units with a fire resistance rating of more than 20 minutes. They must be tested per ASTM E2012 or conform to SFM 12-7a-12, Materials and Construction Methods for Exterior Wildfire Exposure, California Referenced Standards Code‚ Title 24‚ Part 12. This code has been adopted statewide by Utah and Washington and by several local jurisdictions, especially in Arizona.
Green Performance Code
The 2012 IgCC, International Green Construction Code, has not been adopted on a statewide basis, but has been implemented by several local jurisdictions, especially in Arizona and Washington. It is applicable to all construction types except low-rise residential and references ASHRAE/IES 189.1. For example, material selection requires 55% recycled or recyclable materials (by cost or mass) in a qualifying product. Prescriptive energy requirements exceed the IECC by ten percent. Air leakage requirements are the same as those in IECC, and daylighting is required in 50 percent of occupied floor area.
The latest legislative code change initiatives in the Western Region states and their current status can be tracked by visiting the Western Region Building and Energy Code Activity Report on the Members Only State Code and Legislation web page. Individual state code activity can also be found on this page. Additional code-related information can be obtained at www.reedconstructiondata.com/building-codes.