Forward-Thinking, Solar-Ready Commercial Roof Design

By Samantha Corbel, PE; Jacob Ringer, EIT; and John Karras, PE

RECENT ENERGY CONSERVATION code
updates in various North American
jurisdictions have introduced requirements
for new and significantly altered roofs to
be solar-ready. In Appendix CB, the 2021
International Energy Conservation Code
(IECC)1 defines the term “solar-ready” as
having “a section or sections of the roof
or building overhang designated and
reserved for the future installation of a
solar photovoltaic or solar thermal system.”
Currently, it is possible to approach the solar-ready
requirement by denoting rooftop space
for future PV panels on a roof plan, which is
the minimum threshold for compliance. For
example, the energy conservation code in
Washington, DC2 (where the authors reside),
requires that the building design “show
allocated space and pathways for future
installation of on-site renewable energy
systems…to cover no less than 25% of [the] horizontal projection of the gross roof area.”
This and similar code provisions do not
require rooftop renewable energy systems
(e.g., PV panels) to be installed when the base
building construction is complete.
The building owner will typically engage
a PV vendor (many of whom can provide a
variety of helpful “turnkey” services) when
they are ready to implement the PV system.
However, engaging a PV specialist after the base
building construction is complete may result in
a disconnect in timelines and communication
with the base building project team members.
In the meantime, simply allocating a portion of
the gross roof area during the initial building
design—though a productive incremental step
toward increasing on-site renewable energy
on new buildings—does not account for the
multidisciplinary base building design decisions
that must often be considered and coordinated
for a successful future installation of PV panels. A
Canadian Roofing Contractors Association article
titled “Photovoltaics in Roofing”3 aptly notes, “If
not carefully planned, not only can the hoped-for
return on investment in solar quickly evaporate,
it can result, instead, in significant financial loss
and jeopardize the performance of the roof on
which it was installed.”
A proactive approach during initial roof and
building design can contribute to a successful
and predictable implementation of rooftop PV
panels, maintaining the roofing assembly’s
performance and mitigating the potential
for surprises, such as unexpected costs or
constrained options to the building owner.
These proceedings compile a set of forwardthinking,
solar-ready roof considerations for
low-slope membrane roofs (not including
electrical design, which is outside the scope of
this content) that go beyond roof area allocations
and can guide design professionals and other
project stakeholders, regardless of whether
their jurisdiction regulates solar readiness. As a
key member of multidisciplinary project teams
for commercial, institutional, and multifamily
base building designs, the building enclosure
consultant is well-positioned to help keep these
topics at the forefront of design/development
teams’ thought processes.
ROOFTOP PV BASICS
It is helpful for the base building design team
and other project stakeholders to embark on
a solar-ready building design with a baseline
understanding of PV technology and strategies
available to attach the rooftop PV system.
Solar panels consist of PV cells designed to
generate electricity when exposed to radiant
energy, such as sunlight. Sunlight (i.e., solar
radiation) is absorbed by the semiconductors that
make up PV cells, resulting in electrical charges
within the cells that then generate electricity.4
These PV cells are packaged together to create
modules, which can be grouped into panels. The
assembly of PV modules or panels with a support
structure and other ancillary components
(e.g., wiring, junction boxes, monitoring devices)
is referred to as a PV array. PV arrays produce electrical power for the building, which can
reduce the required demand for external energy
from the local power grid.
PV arrays are typically supported by and
attached to a framed structure referred to as a
rack (Fig. 1). Attaching the rack to the building
structure is a critical design decision that impacts
various aspects of the roofing assembly. The
most common attachment methods include
ballast, dunnage/stanchion, mounts with
through-fasteners, and hot-air-welded clips. Thinfilm
PV laminates, some of which can be adhered
to thermoset, thermoplastic, or modifiedbitumen
membranes under the umbrella of the
building-integrated PV philosophy, have not
been part of the authors’ projects in recent years
and are therefore outside the scope of these
proceedings.
In a ballasted assembly (Fig. 2), the PV rack
is typically attached to plastic or metal trays
that are loaded with concrete blocks, pavers,
or other weights to secure the PV assembly
and counteract wind uplift pressures. Typically,
ballasted PV assemblies have a low profile, and
the panels are close to the roof membrane.
This approach avoids rack/mount penetrations
through the roofing membrane, minimizing
the opportunity for such penetrations that, if
poorly flashed, can act as vulnerabilities for water
leakage. Ballasted PV systems are also typically
the most economical attachment method.
However, ballasted systems have several
disadvantages that must be considered. Since
the PV panels are close to the roofing membrane
and the ballast trays rest on the membrane, this
approach can impede roof drainage and cause
heat buildup between the PV panels and the
membrane, which can negatively impact the PV
panel and roofing performance.5 Additionally,
the PV assembly must be removed to access
the roofing assembly for maintenance, repair,
or replacement. Finally, the ballasted trays can
shift in service, especially if adequate expansion/
contraction measures are not designed into the
system, potentially abrading or damaging the
membrane.
In a dunnage approach (Fig. 3), the rack is
mechanically attached to steel framing and
localized posts (e.g., at the corner of each
dunnage frame) that transfer the PV system’s
structural load to the building, often at
underlying columns. Like dunnage (but with
increased roofing penetration frequency),
stanchions (Fig. 4) are composed of a series of
repeating small-diameter posts that transfer
the structural load to the roof deck or building
structure. Both dunnage and stanchions elevate
the PV panels above the roof surface. This allows
for beneficial airflow under the panels and,
depending on how tall the dunnage system
is, allows for roof maintenance, repair, or
replacement without disrupting the PV assembly.
For both dunnage and stanchions, the posts are
flashed with roofing membrane in a detail that,
provided it follows the membrane manufacturer’s
instructions, is typically warrantable.
Another attachment option, for which
commercially available options and
partnerships with membrane manufacturers
have increased in recent years, is PV roof
mounts with through-fasteners (Fig. 5). These
mounts generally consist of metal disks that
attach to the roof deck and either rely on a
gasket seal for water tightness or include an
integral flange of exposed membrane roofing
(e.g., polyvinyl chloride [PVC], thermoplastic
polyolefin [TPO], modified bitumen) that
is adhered or heat-welded to the roofing
membrane. Manufacturers of through-fastened mounts typically have slope limitations
(e.g., 2:12 maximum or 1:12 at areas of high
snow load). This approach is generally more
economical than dunnage/stanchions but
requires numerous penetrations through the
roofing membrane and may have limited
structural capacity relative to other attachment
methods. Unless each mount is raised onto a
curb, the systems may present an increased
vulnerability to water leakage versus the
dunnage/stanchion approach. The membrane
penetration points have varying sealing features,
depending on the specific product, and their
low position puts them in the roof’s drainage
path. This approach also has similar drawbacks to
ballasted systems associated with the PV panel’s
low-profile above the roof surface.
For PVC roofing assemblies, hot-air-welded
clips (Fig. 6) are another newer attachment
option. These clips are proprietary (and
consequently offered by limited manufacturers),
and they avoid rack/mount penetrations through
the roofing membrane by using the roofing
assembly to resist wind uplift pressures rather
than attaching directly to the roof deck or
building structure.
STRUCTURAL
CONSIDERATIONS
Considering future PV installation during the
base building structural design is essential to
a holistic rooftop solar design. The building’s
structural system is interdependent with the
attachments discussed in the previous section
and may unexpectedly restrict the ability
to install future PV panels if not sufficiently
considered. The following sections discuss select
base building structural considerations that the
project’s structural engineer can oversee.
Dead and Live Loads
Section 1606.4 of the 2021 International
Building Code (IBC)6 requires that the weight of
the PV array and its support system or ballast
is included as a dead load when designing the
roof structure. The design of the roof structure is,
therefore, interdependent with the type of the
future PV assembly. Ballasted systems, relative
to other attachment systems, more uniformly
distribute their dead load across the roof deck,
while stanchion systems impose concentrated
point loads on the building’s structure at each
post. Steel dunnage systems, which typically
impose greater concentrated dead loads than
stanchions, consequently require particular
coordination with the base building structure.
Design professionals should consult with
the building owner and structural engineer
regarding what type of support system they
envision for the future and plan accordingly
by designing the base building structure with
adequate reserve capacity for PV dead loads
that can be reasonably anticipated. If dunnage
systems are anticipated, the base building
design may go so far as to identify specific future
dunnage layouts and structural capacity at the
associated future post locations.
Additionally, section 1607.14.4.1.1 of the 2021
IBC requires that the roof be designed for live
loads both with and without the PV panels, so the
base building structural engineer should capture
future PV-related live loads for the area planned
for future PV.
Deflections and Ponding
If the future PV will be a ballasted system,
section 1607.14.4.5 of the 2021 IBC requires that
the roof structure be designed and analyzed for
deflections per section 1604.3.6 and ponding per chapters 7 and 8 of ASCE 7.7 The authors have
investigated outcomes where the addition of a
ballasted PV assembly resulted in ponding at areas
of localized deflection in the roof structure (Fig. 7)
and in the displacement of the roofing base
flashing at the perimeter of the roof, resulting in
water leakage to the interior.
Wind, Snow, and Seismic Loads
Sections 3111.1.1 and 1607.14.4.2 of the 2021 IBC6
also require that rooftop-mounted PV systems be
designed for wind loads in accordance with section
1609, which references chapters 26 to 30 of ASCE
7,7 and that snowdrift loads created by PV panels
(if applicable) be included as dead load.
Besides the IBC, other industry codes and
standards, such as those published by the ASCE
(which the IBC references) and the Structural
Engineers Association of California (SEAOC),
include requirements or guidelines for the
structural design of rooftop PV. The 2016 edition
of ASCE 7, Minimum Design Loads and Associated
Criteria for Buildings and Other Structures, added
new provisions for determining wind loads on
PV panels. ASCE 7-16 also states that solar panels
should be considered as roof projections that may
cause windward drifts on the roof around them,
and it includes provisions for how to calculate
the snowdrift geometry and loading.7 Therefore,
the base building design should assume a
conservative weight for the solar-ready portion of
the roof and/or perform a proof-of-concept analysis
for the snowdrift of the future PV assembly. As
always, project teams must utilize the latest
applicable versions of codes and standards since
their evolutions are likely to affect solar-ready
building designs. For example, ASCE 7-22 includes
increased structural design loads (e.g., snow loads
and rain intensities) relative to earlier versions.
Where applicable, seismic loads must
be considered as they relate to the PV array
and the associated load path to the building
structure. Three reports SEAOC has published
provide structural seismic requirements for
rooftop PV (PV-1),8 include requirements and
recommendations for wind design for solar arrays
(PV-2),9 and address key issues for evaluating the
capacity of the building roof structures to support
gravity loads imposed by PV arrays (PV-3).10 Even
where these provisions are not triggered by a
project’s governing codes, they can be helpful
tools for design teams performing due diligence
or proof-of-concept exercises to prepare a current
base building for future rooftop PV.
FIRE-RELATED/COMBUSTIBILITY
CONSIDERATIONS
Sections 1505.1 and 1505.9 of the 2021 IBC include
requirements for fire classification of the roofing and
PV assemblies based on the building construction
type and reference additional requirements in
the International Fire Code (IFC)11 and standards
by the National Fire Protection Association. When
preparing a new building design that anticipates
future rooftop PV, these provisions are worthy of an
upfront understanding, particularly those related
to firefighter access.
Access Pathways for Firefighters
Section 1205.3 of the 2021 IFC11 requires
pathways to support firefighters accessing roofs
with PV arrays. These requirements vary between
Group R-3 buildings (mainly smaller residential
buildings) and all other buildings (which include
commercial construction). For commercial roofs,
the code prescribes the following minimum
pathway widths and spacing based on the
location and application:
• Minimum 6 ft (1.8 m) wide perimeter pathway
around the edges of the roof (exception: where
either axis of the building is 250 ft [76 m] or
less, the width may be reduced to 4 ft).
• Minimum 4 ft (1.2 m) wide interior pathways at
minimum 150 ft (46 m) intervals, in a straight
line to roof standpipes or ventilation hatches,
around roof access hatches, and (minimum
one) pathway to the parapet or roof edge.
• Minimum 4 ft wide pathways bordering all
sides of non-gravity-operated smoke/heat
vents.
• Minimum 4 ft wide pathways on minimum
one side of gravity-operated dropout smoke/
heat vents.
• Between array sections: minimum 8 ft (2.4 m)
wide pathway or minimum 4 ft wide pathway
bordering 4 ft by 8 ft venting cutouts every
20 ft (6 m) on alternating sides of the pathway.
The geometry of the roof and the layout of
rooftop mechanical equipment and roof hatches
can significantly impact and, in some cases,
limit the layout of future rooftop PV, especially
with consideration of the aforementioned access
requirements. Accordingly, when determining
the portion of the roof that will be allocated for
future PV panels, it is prudent to conduct a proofof-
concept layout process that maps out these
pathways, especially if the building owner is
relying on the PV assembly to provide a minimum
power output that is based on a panel layout that
consumes the allocated square footage.
MECHANICAL, ELECTRICAL,
AND PLUMBING
CONSIDERATIONS
Electrical Pathways/Penetrations
The future rooftop PV system will require
electrical conduits to route through the building
and penetrate the roof, and some solar-ready
roof designs generically require providing
conduits with the base building project for
the future PV. Deferring the identification of
conduit pathways and penetration points/
methods to the future can lead to limited
choices and possibly compromised decisions
and performance problems. Therefore, it is good
practice to incorporate these features, with some specificity, in the base building design.
Regarding conduit runs in the building, allocate
and label space within ceiling cavities, vertical
chases, or other suitable pathways. Do not
route electrical conduits through the roofing
insulation above the structural roof deck; the
authors have investigated existing buildings
where this approach was used, resulting in
a concealed safety hazard for future roofing
contractors (Fig. 8). Moreover, the National
Roofing Contractors Association (NRCA) also
recommends against this practice, adding that
conduits should not be routed through flutes
in steel decks or directly mounted to wood decks.
Regarding electrical penetrations through
the roofing assembly, collecting and routing
electrical conduits through enclosures (either
field-fabricated sheet metal using NRCA details
or prefabricated using commercially available
products [Fig. 9]) near or within the future PV area
is a prudent feature to incorporate in the base
design. The availability of these predetermined
and reliable penetration points can help future
electrical contractors and roofing contractors avoid
the temptation to use less-reliable penetration
techniques such as pitch pockets, whose
sky-facing sealant tends to deteriorate in service
and cause water leakage vulnerabilities far faster
than the surrounding roofing membrane.
Mechanical and Plumbing
Equipment Layout
As described earlier, although the detailed layout
of the future PV panels will likely not be included
in the base building design, it is prudent to
consider how the layout of the rooftop mechanical
equipment may impact the available space for
future PV. First, design teams should carefully
consider whether mechanical equipment belongs
on the rooftop in the first place or is better suited
within a protected enclosure such as a penthouse,
which is more conducive to a safe and recurring
preventive maintenance program and less likely
to be a source of water leakage through the roof.
Design teams should endeavor to consolidate
rooftop mechanical equipment, in part to minimize
the number of access pathways required between
and around each unit, which can reduce the overall
square footage of usable area for PV panels.
Additionally, consider how large equipment
(e.g., chillers or air-handling units) or mechanical
penthouses or screen walls will cast shadows and
position the PV area accordingly, since shading or
otherwise obstructing only a small section of a PV
module or panel can reduce its output.12
Roof Drainage Systems
The drainage strategy for the roof should
be coordinated with the anticipated PV
assembly support system and the locations
of the solar-ready areas. The building code
requires provisions for both primary and
secondary (i.e., overflow) drainage on all
roof areas. Roof drainage systems may
include internal roof drains, through-wall
scuppers, and/or gutters—all of which require
access to inspect, maintain, and repair. It is
prudent to avoid installing PV arrays over
roof drains or blocking scuppers, especially
with low-profile attachment systems (e.g.,
ballast, roof mounts, and clips) where
routine maintenance is not possible without
temporarily relocating the PV arrays to access
the drainage system, which would be costly
and impractical.

ROOFING DESIGN
CONSIDERATIONS
Single Ply Roofing Industry (SPRI) aptly
characterizes the importance of roofing
performance, even on roofs with PV: “The
roof’s function is, first and foremost, to protect
the building contents and its people from the
elements.”13 This section discusses several
factors directly related to designing the base
building roofing assembly in the context of its
future use under the PV assembly.
Alignment of Service Life
According to the NRCA, the service life of a typical
PV assembly is approximately 25 years, and the
service life of the average low-slope commercial
roof is 17.4 years.12 With that said, depending
on the type/configuration of the assembly,
membrane type, quality of installation, and
degree of preventive maintenance, some roofing
assemblies can functionally remain in service
for 25 or more years. Endeavoring for the base
building roof to last as long as possible is critical
for establishing reasonable alignment with
the service life of the future PV. Once the base
building roof is installed below an allocated
solar-ready area, the clock begins ticking toward
misalignment of service lives until the PV is
eventually installed. Misalignment (particularly if
the PV implementation does not occur for several
years) can result in a future scenario where costly
removal and reinstallation of the PV assembly
(especially for low-profile attachment systems)
is required to accommodate the first roof
replacement in the building’s life cycle.
Accordingly, enhancing the roofing assembly
in the base building design to prioritize the
length of its service life should be a design
priority. Some fundamental strategies in this
regard include the following:
• Configuring the roof as a protected
membrane assembly, where the membrane
(e.g., a reinforced, monolithic fluid-applied
waterproofing with a track record in this
application) is protected with overburden such
as drainage composite, rigid and moisturetolerant
insulation, and a wearing surface. This
approach typically lends itself more readily to
roofs with a structural concrete deck than with
a wood-framed plywood deck.
• For single-ply roofs, specifying the thickest
membrane in the manufacturer’s standard
offerings (e.g., 80 mil polyvinyl chloride or
thermoplastic polyolefin instead of 60 mil).
• Specifying a cover board below the roofing
membrane for improved puncture resistance
and load distribution (e.g., distributing the
load from ballast trays in a manner that helps
avoid localized insulation compression below
the membrane and consequent localized
ponding).
• Specifying higher-compressive-strength
insulation (e.g., 25 psi instead of 20 psi).
• Including robust flashing detailing at all
penetrations (e.g., avoiding pitch pockets,
specifying prefabricated flashing boots, and
specifying counterflashings at all penetrations
to shield the underlying base flashing).
• If considering a ballasted system for the future
PV, fully adhering the cover board instead of
mechanically attaching it since the shifting of
the ballast can cause the roofing membrane
to abrade against the fastener plates for the
cover board.
Roofing Assembly Warranty
In addition to pre-PV-install inspections and other
solar-related prerequisites, roofing manufacturers
generally have requirements related to the
composition of the roofing assembly. Base
building design professionals should consult
the basis-of-design roofing manufacturers to
understand how the installation of future PV
panels may impact the roofing warranty and
what provisions are necessary to maintain
the warranty at that time. For example, some
manufacturers have specific guidance regarding
membrane attachment and other roofing design
enhancements described in the previous section.
Additionally, some roofing manufacturers have
limitations on the roofing attachment options
that they allow under their warranty, which may
inform the structural design of the base building.
Insurance Requirements
FM Global, a commercial property insurance
company, requires adherence to specific
standards for roofing materials and installation
procedures on FM-insured buildings. FM Global
has published these requirements via Property
Loss Prevention Data Sheets. FM Global Data
Sheet 1-15, “Roof-Mounted Solar Photovoltaic
Panels,”14 incorporates requirements related
to fire and natural hazards for the design,
installation, and maintenance of all roofmounted
PV panels, and this standard was
updated in January 2023. FM Global mandates
provisions that affect the base building
design, including prohibiting multi-ply roofing
assemblies (e.g., modified bitumen) under PV
panels, requiring specific design parameters
such as factors of safety (which can affect
structural load reactions to the base building
structure), and requiring additional ballast
(where ballast is applicable) at specific portions
of the PV array. If a building is insured by FM
Global, then it is critical for the base building
design team to coordinate with FM Global
Approvals staff and the pertinent data sheets to
ensure the design complies with all FM Global
requirements and will be able to comply with any
future requirements during the PV installation.
Roof Maintenance
SPRI recommends that PV array racks be installed
with enough clearance above the roof membrane
for maintenance/servicing, limiting PV arrays
over field seams and penetrations so that they are
accessible, and protecting high-traffic areas with
walkway pads.13 Similarly, the NRCA recommends
rack-mounted PV systems on support stands
(e.g., stanchions) or on curbs with a minimum
clearance of 30 in (760 mm) from walls, curbs,
or adjacent racks and enough room underneath
to facilitate preventive maintenance, repairs, or
replacement.12 In section 9.7 of the NRCA Roofing
Manual: Membrane Roof Systems – 2023,15 the
NRCA provides guidelines for clearance above the
roof surface for equipment support stands based
on the width of the equipment.
BUILDING USAGE
AND MAINTENANCE
CONSIDERATIONS
Though it should, roofing design does not
always consider how the building will actually be
used and maintained, including maintenance
of rooftop equipment and maintenance of the
facade. To help base building design teams
avoid imposing future unnecessary constraints
on the building owner, this section highlights
considerations related to fall protection
required for future work on low-slope roofs and
considerations related to future facade access.
Rooftop Fall Protection
Requirements
The U.S. Occupational Safety and Health
Administration (OSHA) sets and enforces
standards to ensure safe and healthy working
conditions for workers. OSHA’s general industry
standard (§1910.28)16 includes regulations, which
were updated in 2017, for work on low-slope roofs
of existing buildings. The standard essentially
prescribes that employers of those working on
low-slope roofs are responsible for providing
their employees with an approved fall protection
system where fall hazards are present. Key
aspects of OSHA 1910.28’s provisions for work on
low-slope roofs include the following:
• If a worker is less than 6 ft from the roof edge,
they must be protected by a fall protection
system such as a guardrail or personal fall
arrest/restraint system.
• If a worker is more than 6 ft (1.8 m) and
less than 15 ft (4.5 m) from the roof edge,
either they need a fall protection system implement a designated area (e.g., warning
line system) if the work is both infrequent and
temporary.
• If a worker is more than 15 ft from the roof
edge, then, at a minimum, the employer must
implement and enforce a work rule prohibiting
employees from going within 15 ft of the roof
edge without some form of fall protection.
Additionally, sections 1015.6 and 1015.7
of the 2021 IBC require guardrails whenever
components that require service (e.g., rooftop
mechanical equipment and PV panels) or roof
hatches are located within 10 ft (3 m) of a roof
edge, with the exception that guardrails are
not required if personal fall arrest anchorage
connector devices are present to protect workers
in the defined edge zone.
A fall arrest/restraint system typically consists
of a body harness, lanyard, and anchorage to
the building. In conjunction with designating
solar-ready roof areas and with consideration of
complying with the aforementioned standards/
code provisions, it is prudent for design
professionals to incorporate guardrails, fall
protection unit anchors, or travel arrest/restraint
systems in the base building design to facilitate
safe access of roof areas for future workers,
including PV technicians.
Facade Access
Similar to planning for future roof access,
it is prudent to consider how the facade
of the building will be accessed for future
inspections, maintenance, and repairs. While
shorter buildings may be serviced via mobile
elevated work platforms (e.g., scissor lift or
boom lift) or scaffolding, taller buildings in
dense urban areas may require facade access
from the roof. Workers descending the face
of the building, either via a hung platform
(e.g., suspended scaffolds) or rope descent,
would require personal lifelines and anchor
points, and other equipment that is worthy of
coordinating with the solar-ready roof area to
minimize the chances of conflict with future
PV panels. For example, suspended scaffolds
(i.e., swing stages) need unobstructed rooftop
edge space to erect the suspension system
(e.g., beams and counterweights). Also, the
suspension system requires independent
anchorage (i.e., tiebacks) and a pathway for
the tieback cables to attach to a suitable
independent anchor. Design professionals
should consider conceptualizing and/or
overlaying these pathways on an anticipated
PV panel layout to avoid future facade access
limitations for the building owner.
OTHER RESOURCES
As rooftop PV has become more common in
recent decades, various agencies and industry
associations have published helpful resources
for building owners and design professionals.
For example, the National Renewable Energy
Laboratory, affiliated with the Department of
Energy, has several guides that enumerate highlevel
considerations, discuss policy updates, and
provide cost-benefit analyses for building owners.
Building owners and design professionals may
benefit from these resources in addition to those
listed at the end of this paper.
CONCLUSION
When tasked with solar-ready low-slope
commercial, institutional, or multifamily building
designs, project teams (aided by the guidance
of the building enclosure consultant) can
contribute to a successful future PV and roofing
system by considering the following forwardthinking
steps:
• Work with the project’s structural engineer of
record and other team members (including
PV specialists) to conceptualize the future PV
support system and its various loads so they
can design the base building structure with
adequate reserve capacity that meets the code
and avoids performance issues.
• Identify mandatory access/maintenance
pathways to prepare for future compliance
with fire codes, coordinate with rooftop
equipment and roofing maintenance needs,
and inform the solar-ready area designated
in the base building design. Also, consider
how the roof and facade will be accessed, in
conjunction with considering how the PV array
will be accessed, when laying out solar-ready
roof areas.
• Design the roofing and rooftop MEP systems
in the base building with the future PV
system in mind rather than entirely deferring
PV-related considerations such that they
are not able to be coordinated with base
building decisions.
• Specify a durable roofing assembly with
enhancements that will prolong the roof’s
performance and service life (ideally meeting
or exceeding the service life of the PV array)
and meet roofing manufacturers’ PV-related
warranty requirements.
REFERENCES
1. International Code Council (ICC),
International Energy Conservation Code, 1st
printing (Country Club Hills, IL: ICC, 2021).
2. International Code Council (ICC) and
Government of the District of Columbia,
“Section 5.4.4 On-Site Renewable Energy
Systems,” in 2017 District of Columbia
Energy Conservation Code, 1st printing
(Country Club Hills, IL: ICC, 2020).
3. Canadian Roofing Contractors Association
(CRCA), “Photovoltaics in Roofing,” CRCA
Technical Bulletin, Volume 57, November
2010, https://roofingcanada.com/bulletin/
photovoltaics-in-roofing/.
4. Solar Energy Technologies Office, “How
Does Solar Work?” Office of Energy
Efficiency & Renewable Energy, U.S.
Department of Energy, accessed June 3,
2024, https://www.energy.gov/eere/solar/
howdoes-solar-work/.
5. Keegan, Jennifer, “CEU: Commercial
Rooftop Solar Design Explained,” Building
Enclosure, November 2020, https://
www.buildingenclosureonline.com/
articles/89371-ceu-commercialrooftopsolar-
design-explained.
6. International Code Council (ICC),
International Building Code (Country Club
Hills, IL: ICC, 2021).
7. American Society of Civil Engineers (ASCE),
Minimum Design Loads for Buildings and
Other Structures, ASCE/SEI 7-16 (Reston, VA:
ASCE, 2017).
8. Structural Engineers Association of
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ABOUT THE AUTHORS
Samantha Corbel is
an engineer for the
Loan Programs Office
at the Department
of Energy. She
previously worked as
a building enclosure
consultant for Simpson
Gumpertz & Heger
(SGH) Inc.’s Building
Technology group.
Sam is experienced
with new design, construction administration,
rehabilitation, and investigation projects
for owners, architects, and clients in the
DC, Maryland, and Virginia areas. She has
investigated roof leakage related to PV panels
and consulted with architects regarding Net
Zero and on-site renewable energy goals.
Jacob Ringer
joined Simpson
Gumpertz &
Heger (SGH) Inc.’s
technical staff in
the Washington,
DC, office in 2022.
He is experienced
with enclosure
consulting for a
variety of project
types including
commissioning, rehabilitation, and
investigation, as well as with dispute
resolution and building science.
John Karras is a principal
in Simpson Gumpertz &
Heger (SGH) Inc.’s Building
Technology group. He has
over 20 years of building
enclosure consulting and
construction management
experience on commercial,
institutional, government,
and multifamily buildings.
He serves architect,
building owner, and
contractor clients while designing, investigating,
and rehabilitating building enclosure systems on
a variety of building types. His responsibilities
include design consultation, preparation of design
documents, field investigation, and construction
administration related to building enclosure
systems such as below-grade waterproofing,
roofing, exterior wall claddings and weather
barriers, and fenestration/glazing systems.