Background on ICC Model Codes
The ICC’s International Building Code (IBC) applies to all buildings and structures except those covered by the International Residential Code (IRC). The IRC applies to detached one- and two-family dwellings and townhouses not more than three stories above grade in height (IRC R101.2). Both the IBC and the IRC apply to ‘the construction, alteration, movement, relocation, enlargement, replacement, repair, equipment, use and occupancy, location, maintenance, removal, and demolition of every building or structure or any appurtenances connected or attached to such buildings or structures’ (IBC 101.2). Both the IBC and the IRC refer to the National Fire Protection Association (NFPA) 70, National Electrical Code. PV systems must comply with Article 690 and all other requirements in the National Electrical Code.
The ICC’s International Fire Code (IFC) establishes ‘the minimum requirements consistent with nationally recognized good practice for providing a reasonable level of life safety and property protection from the hazards of fire, explosion, or dangerous conditions in new and existing buildings, structures, and premises and to provide safety to fire fighters and emergency responders during emergency operations’ (IFC 101.3).
The photovoltaic requirements in the IFC are based on Solar Photovoltaic Installation Guideline, published in April 2008 by the California Office of the State Fire Marshal. The purpose of the document was to provide guidance to the industry and to help fire service personnel identify when PV systems are present, keep electrical wiring protected, and provide access for vertical ventilation operations.
The ICC updates its model codes every three years and published the 2012 editions of the codes in the spring of 2011. State and local jurisdictions have adopted the IBC throughout most of the United States. Many jurisdictions have also adopted the IRC and the IFC. Some jurisdictions adopt the IBC and use that code for residential structures as well. Some jurisdictions adopt one or more of these codes and incorporate local amendments. In addition, jurisdictions take different amounts of time to adopt new editions of the code. Some jurisdictions adopted the 2012 Code in early 2012 and some will take many years to adopt this code edition. In addition, jurisdictions can, and often do, make changes to the model codes. To determine the requirements in a specific jurisdiction requires knowledge of which editions of which codes have been adopted and if any local amendments have been added to the code(s).
You can order the 2012 IBC, IRC, and IFC at: www.iccsafe.org/Store/
PV Related Changes
Codes changes related to PV are located in the IBC, IRC and IFC. Important code changes include:
The IBC now requires that ‘rooftop mounted photovoltaic systems shall have the same fire classification as the roof assembly required by Section 1505’ (Section 1509. 7.2).
A key objective of the code requirement is that the installation of PV does not diminish the minimum safety required for the roof. Roof systems have long received fire classification ratings. These ratings are based on the ability to prevent a fire from penetrating through the roof and the ability to minimize the spread of a fire along the roof surface.
Within the requirements of this section, the requirements of IBC 1509.7.2 will need careful examination in their application. The language of this section states that the fire classification of photovoltaic systems must match the minimum fire classification of the roof assembly over which they are mounted as required in Section 1505. With any rooftop structure, the structure should not degrade the fire resistance properties of the roof, so as not to place the structure and its inhabitants at an unanticipated risk. However, straightforward implementation of this requirement is not possible, as the following paragraphs explain.
Photovoltaic modules are a component of a rooftop mounted photovoltaic system and, while photovoltaic modules can receive a fire classification rating (in accordance with ANSI/UL 1703), there is presently no American National Standard fire classification test or rating for a photovoltaic system. Similarly, no American National Standard fire classification test is presently available for the system that includes the photovoltaic array and the roof assembly. Thus, as currently written, Section 1509.7.2 refers to the fire classification rating of a system that is not yet available.
In the absence of a PV system rating, it may seem appropriate to use the PV module fire classification rating in order to ensure the desired result: preservation of the roof assembly’s original fire classification. However, simply using the PV module fire classification rating may not in all cases provide the desired result.
In 2008 and 2009, rigorous testing by UL and the Solar ABCs revealed that the performance of a system, which includes photovoltaic modules on standoff mounted racks when exposed to fire or flame is not the same as that of a module alone. Currently, modules receive a fire classification rating based on testing of the module alone, not as part of a PV system. The results of these tests show that actual performance of a rack-mounted photovoltaic system exposed to fire or flame is strongly dependent on the mounting geometry of the photovoltaic array and properties of the components that make up the specific module type. (A summary of this research is published in a Solar ABCs report available at: http://www.solarabcs.org/about/publications/reports/flammability-testing/index.html )
As a result of this testing and in consideration of the current requirements of IBC Section 1509.7.2, the Solar ABCs, UL, an ANSI/UL 1703 Standards Technical Panel (STP) working group are actively developing a new test methodology. This is being done in close association with a working group composed of PV industry, roofing industry, standards development, building and fire enforcement community and government laboratory experts. The work product of this effort is being rapidly developed for presentation to the full Standard Technical Panel for UL 1703 for vetting and adoption. When adopted, this new test will be applicable to PV systems and will provide the valid, ANSI standard fire classification rating needed for compliance in the execution of the requirements of Section 1509.7.2. Until a photovoltaic system fire classification test is finalized and adopted, Section 1509.7.2, as written, may not be easily applied.
IBC Section 1509.7.1 establishes the criteria for calculating the minimum design loads for rack-mounted Photovoltaic (PV) systems on roofs. The code specifies that the wind loads shall be calculated using the method prescribed in ASCE-7 for Components and Cladding (C&C) using an effective wind area based on the dimensions of a single unit. This provides guidance for wind load engineering calculations, which were not available previously for PV systems on roofs.
The procedure called for by Section 1509.7.1 is different from the procedure described in the Solar ABCs report, Wind Load Calculations for PV Arrays, which recommends using the Main Wind-Force Resisting Systems (MWFRS) method of ASCE-7 as the design parameter. The Solar ABCs report is available to download at http://www.solarabcs.org/about/publications/reports/wind-load/index.html.
There are pros and cons associated with the use of each of these methods. By definition, MWFRS is an assemblage of structural elements assigned to provide support and stability for the overall structure and receive and transmit wind loading forces from more than one surface. Also from ASCE-7, C&C are defined as elements of the building envelope that do not qualify as part of the MWFRS. While many BIPV or flush mounted modules meet the C&C criteria, the Solar ABCs task team determined that the common method of mounting PV arrays on roofs using a racking system meets the definition of MWFRS. Specifically, the modules and mounting hardware are considered to be a structural system because all the hardware is above the roof surface and forces are applied to more than one surface of the system. Rack mounted PV array modules and hardware are more than a surface-covering element such as a shingle or siding.
The IBC language states that the effective wind area should be based on the dimensions of a single unit frame. For a large rack, this method may be significantly more conservative (i.e. over-estimate wind forces). This small effective area may be appropriate for modules mounted at the perimeter of an array field but interior modules can receive significantly lower forces. Using the single unit as the effective wind area may be appropriate until testing can establish the distribution of wind forces.
The IBC method and the Solar ABCs method each utilize different, though existing methods available in current codes and standards as the basis for the wind load calculations. In the long-term, it is the recommendation of the Solar ABCs that a wind load determination method developed and tested specifically for PV arrays be used rather than analyze PV systems in the same way as other, but dissimilar, components Once developed, these design requirements can be incorporated into the IBC and ASCE standards.
Access and Pathways
The IFC requires access and pathways around solar installations in order to:
-Ensure access to the roof,
-Provide pathways to specific areas of the roof,
-Provide for small ventilation opportunities area, and
-Provide emergency egress from the roof.
For residential buildings, the IFC states that modules should be located no higher than three feet below the ridge and also requires a three-foot access pathway on the side of the array. The code details specific requirements for different roof construction types. For a commercial building, the IFC requires a six-foot clear perimeter around the edge of the roof, or four feet if either axis of the building is 250 feet or less. The code also requires pathways in solar installations on commercial buildings.
Local fire jurisdictions have the prerogative to establish revised requirements that provide alternative means and methods of complicance.
The IFC requires marking to identify PV circuits and disconnects to help ensure that firefighters are aware that a PV system is present. Marking is required at the main service disconnect and DC conduit, raceways, enclosures, cable assemblies and junction boxes.
Location of DC Conductors
The IFC includes requirements for the location of DC conductors to reduce trip hazards, maximize ventilation opportunities, and limit the hazard of cutting live conduit. In addition, the 2011 National Electrical Code (NEC®) includes a number of new sections to address firefighter concerns in the routing of conductors.
Building-Integrated PV Systems (BIPV)
The IBC requirements are different for rack-mounted PV systems and BIPV systems. The changes described above for fire rating and wind resistance apply only to rack-mounted PV systems. In general, BIPV systems must meet the same standards as roofing systems.
Solar ABCs Documents on I-Codes
The Solar America Board for Codes and Standards (Solar ABCs) has released a new white paper, Impacts on Photovoltaic Installations of Changes to the 2012 International Codes (www.solarabcs.org/2012whitepaper), and a new report, Understanding the CAL FIRE Solar Photovoltaic Installation Guideline (www.solarabcs.org/fireguideline) that explain the changes for photovoltaics (PV) in the 2012 International Code Council’s IBC, IRC, and the IFC.
The Solar ABCs serves the PV codes and standards community and has developed these publications to provide a thorough understanding and reasoning behind the 2012 International Code changes.
The white paper provides an overview of new code language related to PV systems within the 2012 IBC and IRC. This language specifies requirements for building-integrated photovoltaic (BIPV) systems and rack-mounted PV systems. For each system type, requirements are given for installation, materials, wind resistance, and fire classification. The white paper is intended to assist code officials, solar installers, and roofing contractors to interpret and use these codes.
The 2012 IFC includes requirements for PV installations, and the Solar ABCs report includes the California solar installation guidelines and the similar 2012 IFC requirements because in May 2010 the ICC approved a revised version of the California guideline for inclusion in the 2012 IFC.
Larry Sherwood is President of Sherwood Associates, a renewable energy consulting firm. Sherwood has over 30 years of experience in the renewable energy field and is the Project Administrator for the Solar America Board for Codes and Standards (Solar ABCs, www.solarabcs.org). Previously, Mr. Sherwood served as Executive Director of the American Solar Energy Society. He is a graduate of Dartmouth College.