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VF-1 Fire Standard Finally
Accepted for Green Roofs
By Kelly Luckett, LEED AP, GRP,
The Green Roof Guy
March 9, 2010
The Green Roof Guy's Column
OK
Green Roof Fans,
Your
wait is over. After three years in the making from members
of
Single Ply Roofing Industry
in cooperation with
Green Roofs for Healthy Cities,
we now have a green roof design guide for minimizing the risk of
fire on green roofs. ANSI/SPRI VF-1 was approved on
January 29, 2010 by the
American National Standards Institute
(ANSI) as
a consensus based standard for the design and construction of green
roofs.
While I am certain
there will be people who are unhappy with new guidelines that alter
the way some of us conduct business, please look past the initial
inconvenience to see this milestone in the North American green
roof movement for what it is: the securing of a place in mainstream
construction through the
International Code Council
(ICC).
No longer can the green roof be deleted from a project due to failure
to comply with the fire code.
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Atlanta City Hall
Greenroof; Photo Courtesy
Bill Brigham, ASLA
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Admittedly, the fire
concerns are only half of the code story as the wind design guide
is still progressing through the ANSI process. However, we
must overcome both the wind and the fire obstacle. Therefore,
this victory is absolutely essential to the development of
the green roof industry.
Without further ado,
please allow me to introduce the VF-1 Green Roof Fire Design Guide:
External Fire Design Standard for
Vegetative Roofs
1.0
INTRODUCTION
This design standard
provides a method for designing external fire resistance for vegetative
roofing systems. It is intended to provide a minimum design and
installation reference for those individuals who design,
specify, and install vegetative roofing systems. It shall be used
in conjunction with the installation specifications and requirements
of the manufacturer of the specific products used in the vegetative
roofing system.
2.0
DEFINITIONS:
The following definitions shall apply when designing
a vegetative roof system.
2.1
BALLAST:
In vegetated roofs; ballast consists of growth media,
the trays or containers used to contain growth media, large stones,
paver systems or lightweight interlocking pavers.
2.2
Border Zone:
The band around the edge of the vegetative plantings,
where no vegetation exists. It is frequently the perimeter of the
roof area.
2.3
Firestops:
Area
capable of stopping the spread of flame.
2.4
Gravel Stop:
A low upward-projecting edge, usually formed from
sheet or extruded metal, installed along the perimeter of a roof
to prevent gravel or other small or lightweight aggregate from being
blown or washed off. The gravel stop also serves as a point of termination
for the roofing system.
2.5
Growth Media:
An engineered formulation of inorganic and organic materials including
but not limited to heat-expanded clays, slates, shales, aggregate,
sand, perlite, vermiculite and organic material including but not
limited to compost worm castings, coir, peat, and other organic
material.
2.6
PARAPET:
A parapet wall is a structure that rises above the
roof edge to provide a wall of varying heights. The part of a perimeter
wall that extends above the roof.
2.7
Penetration:
A penetration is an object that passes through the
roof structure and rises above the roof deck/surface. Penetrations
consist of, but are not limited to, mechanical buildings, penthouses,
ducts, pipes, expansion joints and skylights
2.8
Roof Areas:
For design and installation purposes, the roof surface
is divided into the following areas:
2.8.1
Corners:
The space between intersecting walls forming an angle
greater than 45 degrees but less than 135 degrees.
2.8.2
Corner Areas:
The corner area is defined as the roof section with
sides equal to 40% of the building height. The minimum length of
a corner is 8.5 feet (2.6m).
2.8.3
Perimeter:
The perimeter area is defined as the rectangular
roof section parallel to the roof edge and connecting the corner
areas with a width measurement equal to 40% of the building height,
but not less than 8.5 feet (2.6m).
2.8.4
Field:
The field of the roof is defined as that portion
of the roof surface, which is not included in the corner or the
perimeter areas as defined above.
2.9
Succulent:
a plant with thick fleshy leaves and stems that can
store water.
2.10
GRASSES:
Slow growing, narrow leaved plants. Grasses can be
maintained by mowing.
2.11
Vegetative Roof System:
A Vegetative Roof System consists of vegetation, growth media, the
trays or containers used to contain growth media, large stones,
paver systems or lightweight interlocking pavers, drainage system,
and waterproofing over a roof deck.
3.0
System
Requirements & GENERAL DESIGN
CONSIDERATIONS
3.1
Roof Structure Design or evaluation:
The building owner shall consult with a licensed
design professional such as an architect, architectural engineer,
civil engineer, or structural engineer to verify that the structure
and deck will support fully hydrated growth media, vegetation and
other material or objects installed on the roof deck in combination
with all other design loads.
3.2
Membrane
Requirements:
The membrane specified for use in the vegetative
system shall meet the recognized industry minimum material requirements
for the generic membrane type, and shall meet the specific requirements
of its manufacturer. When the membrane or system is not impervious
to root penetration a root barrier shall be installed.
3.3
Slope:
The Design Standard for Vegetative Roofing Systems
is limited to roof slope designs up to 2 in 12. For slopes greater
than 2 in 12, a design professional experienced in vegetative roof
design shall provide the design and the design shall be approved
by the authority having jurisdiction.
3.4
Fire stops
3.4.1 Walls:
Fire stop walls shall be of non-combustible construction
complying with the applicable building code and extend above the
roof surface a minimum of 36 in (914.4mm).
3.4.2
Fire Break roof areas
shall consist of a class A (per ASTM E108 or UL790)
rated roof system for a minimum 6 ft (1.8 m) wide continuous border.
3.5
Interior Fire Rating:
Steel Decks:
Concrete Decks:
Interior fire resistance shall comply with the design
fire penetration requirements based on use and occupancy and be
determined to meet interior fire resistance requirements for the
system installed beneath the soil media.
3.6
Exterior Fire Rating:
Construct the roofing system inclusive of roof decks, vapor barriers,
insulations, roofing membranes, flashings, roof drainage components,
growth media and vegetation to conform to the designed fire resistance
requirements as determined by the building code for the building
considered.
3.7
Wind Design:
The vegetative roof system shall be designed for wind resistance
before beginning the design process for fire resistance.
Vegetative roof systems shall be designed to the requirements of
SPRI RP 14, “Wind Design Standard for Vegetative Roof Systems” or
other design standards as approved by the authority having jurisdiction.
4.0.
VEGETATIVE ROOF
DESIGN OPTIONS: Fire-resistant vegetative roof
designs include, but are not limited to, the generic systems described
below. Other systems, when documented or demonstrated as equivalent
to the provisions of this standard, are permitted to be used when
approved by the authority having jurisdiction (See Commentary Section
4.0). When there is a conflict between this standard and the wind
design requirements the design with the more conservative requirement
shall be used.
4.1.
GENERIC FIRE RESISTIVE VEGETATIVE SYSTEMS
4.1.1.
SUCCULENT BASED SYSTEMS: Systems where the vegetated portion of the roof is planted
in growth media that is greater than 80% inorganic material, and
the vegetation consists of plants that are classified as succulents.
Non-vegetated portions of the rooftop shall be systems that are
classified ASTM E108, Class A.
4.1.2.
GRASS BASED SYSTEMS: Systems where the vegetated portion of
the roof is planted in growth media that is greater than 80% inorganic
material, and the vegetation consists of plants that are classified
as grass. Non-vegetated portions of the rooftop shall be systems
that are classified ASTM E108, Class A.
4.2.
FIRE PROTECTION FOR ROOF TOP STRUCTURES AND PENETRATIONS: For all vegetated roofing systems abutting
combustible vertical surfaces, a class A (per ASTM E108 or UL790)
rated roof system shall be achieved for a minimum 6 ft (1.8 m) wide
continuous border placed around rooftop structures and all rooftop
equipment.
4.3.
SPREAD OF
FIRE, PROTECTION FOR LARGE AREA ROOFS:
A firestop as described in Section 3.4 shall be used
to partition the roof area into sections not exceeding 15,625 ft2
(1,450 m2), with each section having no dimension greater
than 125 ft (39 m). Incorporate the border zones into expansion
joints or roof area dividers wherever possible.
4.4.
FIRE HYDRANTS:
Access
to one or more fire hydrants shall be provided.
4.5.
BORDER ZONES:
Border zones are required when terminating at a fire barrier
wall.
5.0 MAINTENANCE:
Maintenance shall be provided as needed to sustain
the system keeping vegetative roof plants healthy and to keep dry
foliage to a minimum; such maintenance includes, but is not limited
to irrigation, fertilization, weeding. Excess biomass such as overgrown
vegetation, leafs and other dead and decaying material shall be
removed at regular intervals not less than two times per year. Provision
shall be made to provide access to water for permanent or temporary
irrigation. The requirement for maintenance shall be conveyed by
the designer to the building owner, and it shall be the building
owners responsibility to maintain the vegetated roof system.
Commentary to
VF-1
This Commentary
consists of explanatory and supplementary material designed to assist
designers and local building code committees and regulatory authorities
in applying the requirements of the preceding standard.
The Commentary is
intended to create an understanding of the requirements through
brief explanations of the reasoning employed in arriving at them.
The sections of
this Commentary are numbered to correspond to the sections of the
VF-1 standard to which they refer. Since it is not necessary to
have supplementary material for every section in the standard, there
are gaps in the numbering of the Commentary.
C1.0
INTRODUCTION
Green roofs, also
known as vegetative roofs, eco-roofs, and rooftop gardens fall into
two main categories: intensive is primarily defined as having more
than 6 inches of growing medium, greater loading capacity requirements,
and greater plant diversity, and extensive, defined as having less
than 6 inches of growing media, less loading capacity requirements
and fewer options for plants.
Vegetative
roofs are complex systems consisting of many parts critical to the
functioning of the system. To name a few of the components that
are generally found in the system, but the system is not limited
to these products: insulation, waterproofing membrane, protection
mats/boards, root barrier, drainage layer, filter fabric, growth
media, and vegetation. A vegetative roof may consist of more than
just growth media and vegetation, but include such things as walkways,
water features, stone decoration, and benches.
A vegetative roof may cover the whole roof or share a portion of
the surface with a conventional roof system. They are versatile
systems with many strong attributes including stormwater management,
reduction of the heat island effect, and aesthetics to name a few.
VF-1 is a minimum standard. Manufactures and /or designers
requirements that exceed the standards minimum requirements can
be incorporated into specifications for vegetative roof fire resistance.
While the standard is intended as a reference for designers and
roofing contractors, the design responsibility rests with the “designer
of record.”
C2.1
BALLAST:
Ballast includes the growth media and the trays and containers that
are used to contain growth media. The type of growth media used
as ballast in vegetative roofs can influence the fire performance
of the system. Stones, pavers, and concrete surfaces are often used
as ballast and are non-combustible.
C2.5
Growth Media:
Inorganic materials used as growth media are not combustible, however
media with high concentrations of organic material can support combustion.
Soils with high percentages of organic material can negatively affect
the fire resistance of a system. Currently data is unavailable on
specific growth media blends, but it is known that media with high
loadings of organic material such as peat moss can burn.
Sources for Growth
media specifications are as follows:
From ASTM:
C549-06
Standard Specification for Perlite Loose Fill Insulation
C330-05
Standard Specification for Lightweight Aggregates for Structural
Concrete
C331-05
Standard Specification for Lightweight Aggregates for Concrete Masonry
Units
C332-07
Standard Specification for Lightweight Aggregates for Insulating
Concrete
Test Methods
for Classifying Material:
C117-04
Standard Test Method for Materials Finer than 75-µm (No. 200) Sieve
in Mineral Aggregates by Washing
C136-06
Standard Test Method for Sieve Analysis of Fine and
Coarse Aggregates
D5975-96 (2004)
Standard Test Method for Determining the Stability of Compost by
Measuring Oxygen Consumption.
US
Composting Council: “TMECC” Test Methods for the Examination of
Composting and Compost.
C 2.7
Penetration:
Penetrations may consist of, but are not limited to, mechanical
buildings, penthouses, ducts, pipes, expansion joints and skylights.
These penetrations may be combustible or fire may have a major impact
on their performance. For these reasons, penetrations need to be
protected from fire exposure.
C2.11
Vegetative Roof System:
Vegetative roof systems will go over both loose-laid,
mechanically fastened, and fully adhered roof systems. However,
when a mechanically attached roof system is used special precautions
need to be taken to prevent damage to the membrane due to the fastener
and plates below the membrane and impact damage and wear that can
occur at these locations. Mechanically attached systems should not
be used unless approved by the membrane supplier of vegetative roofs,
and all precautions from the supplier are followed.
There are several
types of vegetative roof systems as noted below, and they can be
interchanged without affecting the fire performance of the system.
Ballasted Vegetative Roof System:
A ballasted vegetative roof system consists of vegetation; ballast
as defined in 2.1, provides waterproofing and includes a membrane
or membrane and substrate materials installed over a structural
deck capable of supporting the system. Membranes are permitted to
be loose laid, mechanically attached or partially adhered to the
roof deck or supporting insulation.
Protected Vegetative Roof System:
A protected vegetative roof system consists of vegetation, growth
media, ballast as defined in 2.1, a fabric that is pervious to air
and water, insulation, and includes a membrane that provides waterproofing
and substrate materials installed over a structural deck capable
of supporting the system. Membranes are permitted to be loose laid,
mechanically attached or partially or fully adhered to the roof
deck or supporting insulation.
Vegetative Roof System Using A Fully Adhered ROOF Membrane System:
A vegetative roof system using a fully adhered membrane system consists
of vegetation, growth media, ballast as defined in 2.1, and includes
a membrane that provides waterproofing and is fully adhered to attached
insulation, or adhered directly to a roof deck.
C3.2
Membrane Requirements:
List
of ASTM references for generic roofing types:
EPDM
ASTM D-4637
PVC
ASTM D-4434
TPO
ASTM D-6878
Hypalon/CPE/PIB
ASTM D-5019
KEE
ASTM D-6754
SBS
ASTM D-6164, 6163, 6162
APP
ASTM D-6222, 6223, 6509
BUR
As defined by the standards referenced in the International Building
code.
Fully Adhered Hot-Applied Reinforced Waterproofing
System
ASTM D 6622
Building Height:
Special consideration shall be given when the building height is
greater than 150’ (45.7 m). Vegetative roofs can be designed using
reference 1, consultation with a wind design engineer, or wind tunnel
studies and fire design experience of the specific building and
system.
OTHER
Factors:
There are other factors that affect the design of the vegetative
roof for wind and fire. These include, but are not limited to, building
height, building location, pressurized buildings, large openings,
eaves and overhangs.
C3.5 Exterior Fire Rating:
Building codes are specific as to the requirements
for the roof system fire resistance based on designated occupancy.
Roof systems may be required to obtain ASTM E 108 Class A, B or
C. Data exists that supports the Classification of succulent based
systems as Class A fire resistance. Other systems may be tested
for fire resistance as installed, but the vegetation needs to be
maintained in order to continue to sustain fire resistance. Provisions
need to be made so the vegetation installed on the roof will have
sustainable resistance to the spread of flame as required by the
building code.
C3.6
Wind Design:
Vegetative roofs are not recommended where the basic
wind speed is greater than 140 mph (225 kph). However, they can
be designed using reference 1, consultation with a wind design engineer,
or wind tunnel studies of the specific building and system. The
“authority having jurisdiction” is the only source for approval
of designs not covered in this document. ASCE 7 gives guidance on
how non-standard conditions should be evaluated.
C4.0
VEGETATIVE
ROOF DESIGN OPTIONS:
The Design Options of Section 4 were developed to provide a barrier
to prevent the spread of fire from the vegetative section of the
roof to other parts of the building. These design options were developed
from European experience, forest fire prevention, and roofing experience.
Vegetated “Green Roofs” have an excellent history of resisting fire
damage.
Some vegetation, such as succulents, are very fire resistive. Local
code officials may consider waiving the barrier requirements when
fire resistive vegetation is installed.
ASTM E-108 and UL 790 can be used to test vegetated roof systems.
Modifications of the test standards may be able to provide a meaningful
test for selected conditions. However, with all the plant types
that could be used in a roof design, the varying weather conditions
that occur through the year, and the effects of seasons generate
many variables that limit the potential to classify a roof construction.
For this reason, if the roof is being designed with little or no
maintenance planned; fire rated barriers are required.
Given that wind standards may often require greater areas of non-vegetated
roof, the wind standard will most often determine the size of the
perimeter area or border zones.
C4.2.
Fire Protection for Roof
Top Structures and penetrations:
Pavers are often used as Class A or non-combustible separators.
Care should be taken when installing pavers to avoid damaging the
membrane. Some manufacturers require a separation material between
the paver and the membrane.
C4.3
SPREAD OF FIRE, PROTECTION
FOR LARGE AREA ROOFS: Spread of flame for Class
A fire is limited to 6’ (1.8 m), if there is a 6’ break separating
vegetative areas using Class A material or non combustible material
the flame spread is not expected to ignite the nearby area.
The dimensions chosen for large area roof limitations are based
on FLL and FM requirements, they also coincide with the International
Building Codes Area limitations for Assembly buildings.
C5.0
Maintenance:
The building owner needs to properly
maintain a vegetated roof. One of the important ways of preventing
fires is to keep the roof adequately watered. The need for water
will vary greatly due to climate and types of plants chosen.
Designers should be aware that plantings are to be specific for
the roof being installed and that rooftops are at best hostile places
for vegetation. Removal of dead foliage should occur on a regular
interval, for most roofs and that may be at least once a month.
The moisture level of the growing media should be checked weekly.
By
regularly removing excess biomass that could become fuel for a fire
on the rooftop, the risk of fire spreading beyond the 6 foot (1.8
m) Class A fire rated separation setback to combustible vertical
surfaces is minimized.
Best management practices
for maintenance include regular weeding, fertilization, and removal
of dead/dormant vegetation in accordance with the recommendations
of the green roof provider. Specific directions for the proper maintenance
of the vegetated cover should be furnished by the green roof provider.”
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Industrial Greenroof
in Germany; System: Optigrün; Photo Source: Sarnafil
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Kelly Luckett
References:
1.
Kind, R.J. and Wardlaw, R.L., Design of Rooftops Against Gravel
Blow-Off, National Research Council of Canada, Report No. 15544,
September 1976.
2.
FM Global: Property Loss Prevention Data Sheets 1-35 Green Roof
Systems.
3.
FM Global: Approval Standard for Vegetative Roof Systems Class Number
4477 Draft April 2009.
4.
FLL Standard “Guideline for the Planning, Execution and Upkeep of
Green-Roof Sites”, Forschungsgesellschaft Landschaftsentwicklung
Landschaftsbau e.V. – FLL, Colmantstr, Bonn, Germany.
Publisher's Notes:
Download the
VF-1 Green Roof Fire Design Guide
"External
Fire Design Standard for Vegetative Roofs"
as a PDF
here. Make sure you read all the background info in
The Green Roof Guy's Archives.
Kelly Luckett is President of
GREEN ROOF BLOCKS and
Green Paks and a member of the USGBC. Kelly has been involved
in the industry since 1980, is a LEED Accredited Professional and
also holds a GRP accreditation - Green Roof Professional.
Contact Kelly at:
314.220.2113, or email him at either:
GreenRoofGuy@greenroofs.com
or kelly@greenroofblocks.com.
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