Roof Anchor System for Solar Panels

Scope Images
A PV panel anchoring system
A PV panel anchoring system
Scope

Install a mounting system for solar thermal or solar photovoltaic panels.

  • Consider the roof type (material and slope), weatherproofing, installation convenience, and wind and snow loadings.
  • Choose an appropriate racking and mounting system for the type of PV module, and install the system along with needed flashing and seals.

See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

Description

Photovoltaics (PV) are becoming more common today on the rooftops of homes to capture and convert solar energy into electricity, thereby reducing total energy costs for the homeowner. These may be large PV panels that are assembled into an array or PV shingles that are used in place of standard roofing shingles. Solar thermal systems for heating water are installed on the roof in the same way the PV panels are installed.

When adding any type of solar array on the roof of a newly constructed house, it is important to choose an appropriate and well-designed racking and mounting system that can provide structural support to the solar modules and to properly flash the mounting blocks and integrate the flashing with the roof underlayment and roof covering to ensure the integrity of the roof.

Several types of roof racking and mounting systems are available on the market by various manufacturers. Although each manufacturer has its own uniquely designed mechanisms, the systems generally have the same basic components. For PV modules, the racking and mounting system typically consists of the following:  a two-railed track that is bolted into the rafters and onto which the panels are clamped, a flashing component for weatherproofing the penetrations, and all required hardware such as bolts and clamps. Some systems eliminate the need for the rails, thereby removing those additional connections. If integrated roof modules (e.g., PV shingles) are installed, no additional mounting system is needed. Photovoltaic shingles can be fastened directly to the roof deck like standard roofing shingles. This installation typically takes place when the roof covering is being installed and would require only one roofing contractor who is experienced in installing PV shingles.

Another factor is whether the roof slope will be suitable for the PV modules or if additional slope needs to be added via the roof mount system. 

A roof mounting system for a PV system
Figure 1. Roof mounts are installed on the roof to support PV panels. (Source: IBACOS 2014).

 

The PV panel layout must also address the requirements of IRC Section 324 Solar Energy Systems. These requirements specify firefighter access to the ridge with a 36-inch-wide clear path for the full length of the ridge and two paths from the eave to the ridge as well as a 36-inch-wide clear path from the eave to any egress windows that open to the roof; plumbing vent locations; structural requirements; and roof penetrations. See the Compliance tab for additional code-related details.  

When choosing a rack and mounting system, factors such as the roof material, roof slope, weatherproofing, installation convenience, and wind and snow loads should be taken into account. Certain mounting systems may be specific to particular roofing materials or slopes or may be able to function with all roof types. Masonry roofs may require additional structural considerations because of the extra weight of the roof tiles.

Roof Penetrations, Flashing, and Roof Attachments

With the exception of raised-seam metal roofs, most roof types require penetrations for rack mounts. In the best installations, standoffs, lag screws, or bolts tie into structural members. All brackets should have butyl tape or a high-quality caulking such as polyurethane or polysulfide, to seal any bolt penetrations and under struts, brackets, or mounting feet.

If standoff mounts or other brackets can be installed before the roofers install the finished roof, roofers can more easily shingle or tile around the flashing and may install the flashing for the mounts. This approach helps to ensure that the roof warranty is intact. Solar installers need to coordinate with roofers prior to the installation to ensure warranty issues are addressed, proper flashing materials are on hand, and installation procedures have been worked out.

Weatherproofing is an extremely important element of a PV anchoring system. Because many penetrations will be made in the roof to secure the mounting system, it is critical to ensure that leaks do not develop from those penetrations. In the past, sealants alone were used to waterproof the penetrations, but this became problematic because the sealant often would break down from the impacts of the ultraviolet rays from the sun, oxidation, expansion and contraction, and wind and other vibrations. Therefore, a better practice is to have additional weatherproofing in place, including flashing. The IRC now specifically requires that roof penetrations for rooftop PV systems be flashed and sealed. See the guides Flashing of Penetrations in Existing Roofs and Roof Deck Valleys and Penetrations Sealed for flashing details for roof penetrations.

Wind Loads

There are two structural concerns: dead load, the weight of the systems bearing on the roof, and live loads, the intermittent loads created by wind, snow, and maintenance people. Collectors should never be supported by roof sheathing between structural members. The project structural engineer or truss designer should be involved early in the design process. Even if not needed to accommodate the load, additional framing may be added as blocking for installing the anchors even if structural loads are within limits. Design wind loads for PV panels and other structures are defined in the American Society for Civil Engineers Minimum Design Loads and Associated Criteria for Buildings and Other Structures, ASCE/SEI 7-16.

Dead loads are typically minimal in PV arrays, no more than 5 to 10 lbs/ft. However, the loads are often transferred to the rooftop through mounting devices that concentrate the array dead loads onto small surface areas of the roof or individual load-bearing members. These conditions can significantly add to the loading conditions of a single truss, rafter, joist, decking, or other roof component. Live loads can be large in magnitude, but are intermittent and are attributed to wind, snow, and maintenance personnel. Most PV modules are rated for a dead loading of 50 to 55 lbs/ft2 or equivalent to the pres­sure of constant 110 to120 mph winds (Barkasi and Dunlop 2001).

Designing mounting systems for wind uplift is more critical in areas subject to hurricanes and excessive wind speeds. Manufacturers of collectors, modules, and mounting systems typically have their mounting systems pre-engineered for worst-case wind loads (DEG 2005). In parts of the world that are vulnerable to hurricanes or extreme wind storms, the collector and its mounting structure need to be able to withstand intermittent wind loads from 115 to180 miles per hour depending on the wind zone in which the home is being built. This corresponds to a pressure of about 75 pounds per square foot (FSEC 2006). Rudin and Becerra (2006) describe approaches for analyzing severe wind loads.

Wind loads may be greater near the roof ridge. Mounting collectors or arrays near the ridge may increase wind loads on the equipment (FSEC 2006). Similarly, locating collectors and arrays in from eaves may reduce wind loads (Rudin and Becerra 2006).

Good engineering cannot make up for poor installation. It is easy to miss structural members when fastening mounting systems to the roof. Care must be taken to ensure that fasteners are correctly positioned. Failure of a bolt to torque down is a clear indication the structural member has been missed. Also, bolts shorter than those recommended by the manufacturer should not be used. Mounting systems can be secured to structural blocking placed between rafters/trusses if the layout of rafters/trusses does not align with the desired collector location. All bolts securing collectors or modules to racks or brackets must be securely tightened. Here are a few things to consider for PV anchoring systems in hurricane-prone regions:

  1. Specify double-nutting of the panel clamp bolts. For the first nut, specify nuts that are furnished with T-bolts. For the second nut, specify a stainless-steel lock nut with a nylon insert.
  2. Specify that all bolted connections are made with a calibrated torque wrench and torqued as specified by the PV system manufacturer.
  3. Specify that PV panels are not installed over roof drains and that walkways are provided to each drain so that drains can be easily checked for debris, and cleaned and maintained as appropriate. (FEMA Rooftop Solar Panel Attachment 2018).

For ensuring success, proper maintenance of the system is also necessary. The property owners or operators should have maintenance staff or a contractor annually check the tightness of the PV array’s bolted connectors with a torque wrench. All the panel clamps should be checked and spot checks should be made for bolts that connect rails to clip angles or posts. (FEMA Rooftop Solar Panel Attachment 2018).

Use a reputable contractor with experience in PV installation to help ensure that the installation is done correctly. Insist that PV installers meet with other trades to work out equipment compatibility, supply, and installations issues. For example:

  • Roofers need to know what types of flashing to use, who will be installing it, and when. Roofers also need to know if PV tiles will be used that will replace sections of the roof.
  • Trades requiring roof penetrations need to know what areas are off limits for vents or other elements that may shade the PV. This coordination issue was the number one area of difficulty identified by PV installers interviewed for this document.
  • PV and solar thermal installers need to know what parts of the roof to use for their systems. Typically the truest southern exposure should go to the PV installation.
  • For long-term performance, landscape designers and installers need to keep the southern exposure unobstructed from trees and outbuildings.
  • Painters and stucco crews need to take all steps necessary to avoid overspray.

Be sure that the PV panel system is properly grounded.

Composition Shingle Roofs

Many efficiency programs recommend that on existing homes, roofs should have 10 or more years of useful life remaining (see for example the DOE Sustainable Energy Resources for Consumers program).

Stanchions and hanger bolts can be used with flashing at the mounting points. In new homes, it is best if both the bolt and the stanchion are applied before the roofing is installed. The lag screw end of the hanger bolt is threaded directly into the structure. The stanchion is lag-screwed to the roof structure (into a truss or rafter). After these are placed, a flashing is applied over the bolt or stanchion. Hanger bolts are preferred due to their low cost and quick installation but should not be used with solar thermal systems that use integrated collector storage for structural reasons. Stanchions may be flashed with roof boot type flashing.

Flat (Low Slope) Roofs

Curb mounts work well for flat or low-slope roofs. Elevated racks are often used on flat roofs to provide an appropriate angle for the collector or module. Racks may be mounted on curbs or standoff mounts. Another reason for using racks in colder climates is to place modules and collectors above snow levels. Curb systems are described in the Roofing and Waterproofing Manual by the National Roofing Contractors Association. To avoid putting penetrations in EPDM roofing membrane found on flat/low-slope roofs, other mounting systems are available, including a system that uses a heat gun to heat weld plastic flanges on the mounting brackets directly to the membrane using standard hot-air welding techniques.

Standing Seam Metal Roofs

Clips can attach to raised seam metal roofing that do not require a roof penetration and can be used to clamp racks to the seam (Christian 2006).

Structural Insulated Panel Roofs

As part of a study of affordable ZEH in Tennessee, a process was worked out for installing racks on roofs made with structural insulated panels (Christian 2006). PV attachment is a potential issue due to the lack of rafter framing in SIPS roofs, requiring attachment solely to OSB sheathing. A more recent article in Home Power describes an approach using a toggle bolt (Sughrue 2013). Follow SIP manufacturers instructions. Another potential solution is an engineered “spreader plate” to distribute the point load. Follow SIP manufacturers’ instructions.

Low-Profile Mount

Many PV systems come with arrays, racks, and clips that are designed to mount together. One method of reducing the visual effect of a solar array is to make the mounting system as close to the roof, and as small, as possible. All major PV manufacturers produce PV modules that can be mounted in low-profile racks.

Thin Film Solar Panels

Thin film solar cells use layers of semiconductor materials only a few micrometers thick. Thin film technology has made it possible for solar cells to now double as these materials:

  • Rooftop or solar shingles
  • Roof tiles
  • Building facades
  • Glazing for skylights or atria.
  • Thin-film rooftop or solar shingles, made with various non-crystalline materials, replace typical roofing materials and do not require roof anchors or racks.

Some PV systems are designed to be integrated into roof designs, i.e., to replace roofing rather than be mounted above it. Integrated systems in the U.S. include PV modules that are sized and mounted to replace shingles or concrete roofing tiles. Since these products are replacing roofing material and are the first line of defense against the elements, they should be compliant with local and national roofing requirements.

How to Choose an Appropriate Roof Racking and Mounting System for the most common PV Modules

The following provides a general description of the steps that should be taken to choose the most appropriate roof racking and mounting system for the specific type of PV module being installed on the roof of a house. Standardized design packages with pre-engineered mounting systems and integrated components can substantially reduce installation costs (Ventre et al. 2001).  These systems tend to include documentation such as drawings and instructions that aid with permitting and inspections.

  1. Identify the roofing material and slope. The first step in choosing a roof-mounted PV anchoring system is to identify the type of roofing material that will be installed and the slope of the roof. These parameters will affect the type of anchoring system because the systems differ, based on these elements.
    Roofing material and slope

    Figure 2. Roofing material and slope. (Source: IBACOS).

  2. Identify the type of PV module being installed - panels or integrated tiles (e.g., PV shingles) Some PV shingles do not require any additional mounting hardware, making the following steps irrelevant. Follow the manufacturer’s installation instructions.
     
    PV module installation
    Figure 3. PV module installation. (Source: IBACOS).
     
  3. Choose the most appropriate anchoring system for the project. Once the roof type (material and slope) and the type of PV module have been identified, choose the mounting system. When choosing a system, make sure that it includes the necessary components (as discussed above). Also, consider the efficiency of the installation process and the potential additional loads on the system from wind and snow. Reference the manufacturer’s documentation for the exact product to ensure that the anchoring system will integrate properly with the chosen PV module. Mounting bracket configurations are shown in Figures 6, 7, and 8.
    Anchor system installation
    Figure 4. Anchor system installation. (Source: IBACOS).
     
  4. Verify that installation of the PV modules and anchoring system was completed correctly, according to best practices. When the first row of PV modules has been installed on the anchoring system, check the installation to verify that it was completed to a high standard of quality. Implement quality control and quality assurance procedures to ensure that the design intent is met. This may help to prevent future costs related to weather damage or rework. 
    Completion of the first row of PV panels and quality assurance checks
    Figure 5. PV panel anchors are installed and flashed before installing racks and panels. (Source: IBACOS).
Lag-Bolted L Brackets for Mounting PV Panels to Roof Decking
Figure 6. Lag-Bolted L Brackets for Mounting PV Panels to Roof Decking. (Solar Rating and Certification Corporation 2020).
 
Stanchion Mount for Mounting PV Panels on a Tile Roof. 
Figure 7. Stanchion Mount for Mounting PV Panels on a Tile Roof. (Source: Davis Energy Group 2015).
Hanger Bolt Mounting with Flashing for Mounting PV Panels on a Round Tile Roof
Figure 8. Hanger Bolt Mounting with Flashing for Mounting PV Panels on a Round Tile Roof. (Davis Energy Group 2015).

 

Ensuring Success

Early in the design process, ensure that the correct type of mounting system will be used to integrate the PV modules on the roof and verify that the chosen mounting and racking system will be compatible with the PV panels. This can be done by considering the roof material, roof slope, weatherproofing, ease of installation, and wind and snow loadings. Closely examine the manufacturer’s product documentation for all of the systems involved, both early in the design process and throughout the installation.

Early in the project, confirm with local code officials that the mounting and racking system will meet all code requirements. Most jurisdictions require that PV installations are properly flashed and waterproofed according to roofing codes.

Inform the home owners that proper maintenance of the system is also necessary. The home owners should have a contractor annually check the tightness of the PV array’s bolted connectors with a torque wrench. All the panel clamps should be checked and spot checks should be made for bolts that connect rails to clip angles or posts (FEMA Rooftop Solar Panel Attachment 2018).

Climate

The DOE Zero Energy Ready Home PV-Ready Checklist (Revision 07)  is required only under the following condition related to climate (See the Compliance Tab  for other exceptions):

  • The home's location, based on zip code, has at least 5 kWh/m2/day of average daily solar radiation based on annual solar insolation using the PVWatts online tool. See map below. 
Average daily PV radiation per month and amount of kWh/m2 per day
Figure 1. The spread of average daily PV radiation per month over the United States, with the required and recommended amount of kWh/m2 per day. (Source: PVWatts Calculator).

When choosing a racking and mounting system, factors such as the roof material, roof slope, weatherproofing, installation convenience, and wind and snow loads must be considered, particularly in hurricane-prone regions or other high-wind areas. Refer to Chapter 3 of International Residential Code (IRC 2018) for design wind load and other loading conditions. Some local jurisdictions may have additional requirements or require specific product approval. See the Compliance tab for more details. PV array installers and designers can use ASCE/SEI 7-16 Minimum Design Loads for Buildings and Other Structures for determining dead, live, soil, flood, tsunami, snow, rain, atmospheric ice, earthquake, and wind loads, and their combinations for general structural design.

Designing mounting systems for wind uplift is more critical in areas subject to hurricanes and excessive wind speeds. Manufacturers of collectors, modules, and mounting systems typically have their mounting systems pre-engineered for worst-case wind loads (DEG 2005). In parts of the world that are vulnerable to hurricanes or extreme wind storms, the collector and its mounting structure need to be able to withstand intermittent wind loads from 115 to180 miles per hour depending on the wind zone in which the home is being built. This corresponds to a pressure of about 75 pounds per square foot (FSEC 2006). Rudin and Becerra (2006) describe approaches for analyzing severe wind loads.

Wind loads may be greater near the roof ridge. Mounting collectors or arrays near the ridge may increase wind loads on the equipment (FSEC 2006). Similarly, locating collectors and arrays in from eaves may reduce wind loads (Rudin and Becerra 2006).

Design Guidance

Here is design guidance for anchoring PV systems in hurricane-prone regions: (from FEMA Rooftop Solar Panel Attachment: Design, Installation, and Maintenance 2018).

As an initial step in the design process, it is recommended that designers calculate wind loads on PV arrays in accordance with ASCE 7- 16 or the local building code, whichever procedure results in the highest loads. It is recommended that the design criteria in SEAOC PV2- 17 also be considered. Note, the Risk Category for rooftop PV is required to be not less than that for the building on which the equipment is located, nor that for any other facility to which the equipment provides a necessary service (ASCE 7-16, C29.3.1).

Hurricane-Prone Regions

  • Recommend mechanically anchored PV rails or racks be specified, rather than ballasted racks, or rails/racks that are attached to the roof surface with adhesive.
  • Specify panels that have a VSH rating per FM 4478.
  • Recommend using microinverters where appropriate. Although these generally cost more than central or string inverters; they have several advantages. Unlike string inverters, microinverters have a greater chance of allowing undamaged panels of a PV array to continue to produce electrical power even if one panel is blown away or damaged by wind-borne debris. In an array using string inverters, if one panel is damaged, all the panels on the string will be offline.
  • Recommend configuring PV power systems such that they can provide power to the building even if the municipal power is not operational.

For all regions:

  • Specify PV panels that have sufficient uplift resistance to meet the calculated wind loads. Also specify the panel attachment to rails/racks, specify the attachment of rails/racks to clips or posts, and design the attachment of the clip or post to the roof support structure and/or the roof deck. If attachment is to the roof deck, verify that the deck has adequate attachment to resist the additional uplift load imparted by the clips or posts.
  • Specify PV panels and rail/rack systems that have UL 1703 and UL 2703 listing (as applicable), and an ICC AC 428 evaluation report. If the building is insured by FM Global, specify that the PV system have an FM 4478 approval.
  • Specify double-nutting the panel clamp bolts. For the first nut, specify nuts that are furnished with T-bolts. For the second nut, specify a stainless-steel lock nut with a nylon insert.
  • Specify that all bolted connections be made with a calibrated torque wrench and torqued as specified by the PV system manufacturer.
  • Specify that PV panels are not installed over roof drains and that walkways be provided to each drain so that drains can be easily checked for debris, cleaned and maintained as appropriate.
  • Specify a walkway between rows of PV panels so that bolted connections can be checked annually.

Wind-Borne Debris

Neither ASCE 7, IBC, IRC, ICC AC 428, nor FM 4478 has wind-borne debris requirements for solar panels. In hurricane-prone regions, it is recommended that designers specify solar panels that have a damage rating of “VSH” (very severe hail) per FM 4478.

For seismic considerations, see the Structural Engineers Association of California (SEAOC) report, Structural Seismic Requirements and Commentary for Rooftop Solar Photovoltaic Arrays (SEAOC PV1-2012).

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Compliance

The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

Complete contract documentation as described in this guide is not required by ENERGY STAR HOMES® Version 3/3.1.

DOE Zero Energy Ready Home (Revision 07)

Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
Exhibit 1, Item 7) Provisions of the DOE Zero Energy Ready Home PV-Ready Checklist are Completed.

Community Solar - If a home is served by a community solar system, it does not have to meet the PV-Ready Checklist provisions.

Multifamily - For multifamily buildings, the PV-Ready provisions may be applied to the electric service for the building’s common space instead of being applied to each dwelling unit.

2018 International Residential Code (IRC)

Chapter 15 (Roof Assemblies and Rooftop Structures) discusses waterproofing. See Sections 1503, 1506, and 1507 for details.

Parts of Chapter 9 (Roof Assemblies) and Chapter 23 (Solar Energy Systems) discuss the installation of PV panels and the associated details, including waterproofing.

Section R324 in IRC 2015 and 2018 addresses solar energy system requirements.

For 2018, there are several important updates:

R324.4.1 Addresses structural requirements for dead loads, roof loads, and wind loads for PV systems. The 2015 editions of the IBC and IRC require rooftop PV panel systems to be designed for component and cladding loads. However, the referenced criteria are not specific to PV systems. The PV provisions in the 2018 editions indirectly reference PV wind load criteria in ASCE 7-16.

R324.4.3 Mandates that roof penetrations for PV systems be sealed and flashed in accordance with Chapter 9.

R324.6 New requirements for firefighter access to the ridge, with a 36-inch wide clear path for the full length of the ridge and two paths from the eave to the ridge, and to an egress window that opens to the roof, with a 36-inch wide clear path from the roof eave to the window.

P3103 Allows a solar collector or PV panel to be installed above a plumbing vent if certain criteria are met.

Chapter 9 (Roof Assemblies and Rooftop Structures) discusses weatherproofing. See Sections 903, 906 and 907 for details.

Parts of Chapter 9 (Roof Assemblies) and Chapter 23 (Solar Energy Systems) discuss the installation of PV panels and the associated details, including waterproofing.

National Electric Code (NEC)

Although the code does not impose specific regulations for roof mounting of PV systems, grounding and other electrical requirements are outlined. Each roof mounting system must be properly grounded.

Standards

Several associations are involved in standards development and best practices for roofing, including roofing systems for PV modules:

ASCE/SEI 7-2016 Minimum Design Loads for Buildings and Other Structures

Describes the means for determining dead, live, soil, flood, tsunami, snow, rain, atmospheric ice, earthquake, and wind loads, and their combinations for general structural design. The 2016 edition of ASCE 7 added wind load criteria for rooftop solar panel systems (Chapter 29). Criteria are given for roofs that have slope angles < 7 0 . Criteria are also given for roofs with other slopes, provided that the panels are parallel to the roof slope (with a tolerance of 20).

Structural Engineers Association of California Wind Design for Solar Arrays (SEAOC PV2-17, 2017)

The 2012 edition of SEAOC PV2 formed the basis for the new PV provisions in ASCE 7-16. The 2017 edition of PV2 references the ASCE 7-16 provisions, incorporates knowledge from research since 2012, and provides background and recommendations beyond those in ASCE 7-16. SEAOC PV2-17 also provides example problems and illustrates specific aspects of the calculation methods. SEAOC PV2-17 includes provisions that are not in ASCE 7-16; these are intended to clarify or provide extensions to the ASCE-16 requirements. Following these more detailed provisions of PV2-17 may reduce the design wind load on portions of an array. If these load-reduction procedures are taken, it is recommended that the authority having jurisdiction approve the reduction.

UL Standard for Mounting Systems, Mounting Devises, Clamping/Retention Devices, and Ground Lugs for Use with Flat-Plate Photovoltaic Modules and Panels (UL 2703, 2015)

This standard primarily addresses wind uplift and other issues associated with PV panel mounting systems. It is referenced in the 2015 and 2018 editions of the IBC.

ICC Evaluation Report AC 428, Acceptance Criteria for Modular Framing Systems Used to Support Photovoltaic (PV) Panels (ICC AC 428, 2012)

This report requires all elements of rooftop PV panel systems to be designed for component and cladding pressures per ASCE 7-10. (The 2010 edition of ASCE 7 does not have criteria specific to PV systems.) For friction clips or connections that resist loads through a clamping mechanism, the nuts are required to have a self-locking mechanism intended to prevent the nut from loosening. Special testing criteria are also specified for this type of connection. The manufacturer's installation instructions are required to specify the use of a calibrated torque wrench for torqueing fasteners in friction connections. Special inspection criteria are specified. ICC AC 428 also addresses seismic issues.

National Roofing Contractors Association (NRCA) Guidelines for Rooftop-Mounted Photovoltaic Systems (NRCA 2018)

This document provides guidance on integrating a PV array with a roof system. Discussion is provided on the equivalent service life, wherein it is recommended that the roof system (new or existing) have an expected service life that is equal to or greater than the PV system. This is recommended to avoid having to remove the PV system to replace a roof system that reaches the end of its service life before the end of the PV system's service life. It also provides guidance on enhancements for new roof systems in order to make them "PV ready." Guidance is likewise provided for the design of flashing details at PV system penetrations through the roof covering. The document additionally provides information on a certification program for roofing professionals, "Certified Solar Roofing Professional."

 

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

Existing Homes

Installation and flashing of PV system anchors is similar for both new and existing homes.

More Info.

Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

References and Resources*
Author(s)
Department of Energy
Organization(s)
DOE
Publication Date
Description
Website describing how solar water heaters -- also called solar domestic hot water systems -- can be a cost-effective way to generate hot water for your home.
Author(s)
National Roofing Contractors Association
Organization(s)
National Roofing Contractors Association
Publication Date
Description
Manuals describing design, materials, and installation techniques applicable to almost all types of roof systems; four-volume set includes Metal Panel and SPF Roof Systems, Membrane Roof Systems, Architectural Metal Flashing and Condensation and Air Leakage Control, and Steep-Slope Roof Systems.
Author(s)
U.S. Environmental Protection Agency
Organization(s)
EPA
Publication Date
Description
The RERH specifications and checklists take a builder and a project design team through the steps of assessing a home’s solar resource potential and defining the minimum structural and system components needed to support a solar energy system.
Author(s)
Aldrich
Organization(s)
CARB,
Steven Winter Associates,
SWA
Publication Date
Description
Brochure on specifications for PV systems.
Author(s)
Sughrue
Organization(s)
Home Power
Publication Date
Description
A structural insulated panel (SIP) roof has no embedded lumber in the structure, and therefore nothing substantial for attaching PV array and solar hot water mounts. Single or double lumber splines could be put into the panels, or I-joists at 4-foot intervals could be added.
Author(s)
Federal Emergency Management Agency
Organization(s)
FEMA
Publication Date
Description
A recovery advisory guide providing guidance on existing code requirements as well as recommend best practices for attachment design, installation, and maintenance of rooftop solar panels to increase panel wind resistance in the U.S. Virgin Islands after Hurricane Maria.
Author(s)
National Roofing Contractors Association
Organization(s)
National Roofing Contractors Association
Publication Date
Description
Manuals describing design, materials, and installation techniques applicable to almost all types of roof systems; four-volume set includes Metal Panel and SPF Roof Systems, Membrane Roof Systems, Architectural Metal Flashing and Condensation and Air Leakage Control, and Steep-Slope Roof Systems.
Publication Date
Author(s)
National Fire Protection Association
Organization(s)
NFPA
Publication Date
Description
This standard provides a benchmark for safe electrical design, installation, and inspection to protect people and property from electrical hazards and has been adopted in all 50 states.
*For non-dated media, such as websites, the date listed is the date accessed.
Contributors to this Guide

The following authors and organizations contributed to the content in this Guide.

Building Science Measures
Building Science-to-Sales Translator

Solar Electric Ready Home = Solar Electric Ready Home

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Technical Description

As solar photovoltaic (PV) panels have significantly come down in price, many homeowners are installing them to produce clean power and reduce their electric bills. Many more homeowners are likely to want this option for the future. Solar electric-ready homes make this possible with minimal to no disruption or cost penalty using simple no-cost/low-cost details and best practices integrated during construction. This includes ensuring adequate unshaded roof space for the PV panels, installing conduit from the attic to the electric service panel, securing documentation that the roof is designed to support the extra weight of the PV array, and providing adequate space near the electrical panel for balance of system components.

Solar Electric Ready Home
Sales Message

Solar electric ready homes include additional design features and details that enable solar electric systems to be added in the future with minimal or no cost penalty. What this means to you is that your home is ready to offset all or most of its annual energy consumption with a solar electric system. Wouldn’t you agree it feels great to have the power to eliminate most or all of your utility bill whenever you want?

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