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Would You Like That Roof Supersized?

May 15, 2009

American consumers are
always looking for value, and
we love to have options. Fast
food restaurants with their
medium, large, and supersize
value meals are perfect examples
of our desire for choices. Maybe that’s
one of the reasons that single-ply roofing
now accounts for nearly 50% of the commercial
roofing market, according to a 2007
market share study conducted by NRCA.
The market share continues to grow, with a
diverse selection of roofing options. Highly
reflective TPO membrane is popular in
warm southern climates, while EPDM continues
to be favored in northern markets
where winters are harsh and heating-degree
days outnumber cooling-degree days.
Single-ply membranes can be ballasted,
mechanically fastened, or fully adhered,
resulting in even more choices of fasteners
and adhesives. Finally, regardless of membrane
type, the thickness must also be chosen.
Of all the choices along the way, thickness
may be the most important, though its
significance is often overlooked.
Selecting a thinner roofing membrane
over its thicker counterparts can be a shortsighted
decision, not to mention a costly
one. Whether it’s EPDM, TPO, or PVC, there
are several reasons that a thicker membrane
will deliver both greater performance
and a more solid return on investment.
An Issue of Dollars and Sense
In many instances, cost is the deciding
factor in selecting membrane thickness for
a given project. However, in most cases, the
membrane cost is viewed in the wrong context,
creating a misleading perception of its
effect on the overall cost of the job. For
instance, the increase in material cost from
a 45-mil to a 60-mil single-ply membrane is
slightly more than 20 percent, which might
sound like a hefty increase but is minimal
in relation to the overall installed cost of the
entire roof system. When considering the
additional cost, total installed cost vs.
return on investment is the accurate
A typical project involves costs for
design, insulation, labor, and materials. A
membrane upgrade only affects material
costs. Thicker TPO or PVC membrane can
be welded without changing the welder
speed or temperature settings. EPDM
makes use of the same seam tapes, regardless
of membrane thickness. Detail flashings
do not change based on the membrane
thickness. In either case – thermoplastic or
elastomeric systems – labor and flashing
costs should remain virtually unchanged.
Increasing from a 45- to a 60-mil membrane
typically adds as little as 5 percent to
the cost of the roofing installation. If the
project involves the added expense of a
tear-off, the percentages are even less:
approximately 2-3 percent. However, the
return on investment from making that
switch is substantially improved, as the
projected lifespan of the roof can be
increased by as much as 33 percent.
In almost any situation, most individuals
would pay a little extra for a yield of that
magnitude. That’s how the fast food chains
continue to supersize the American population!
However, unlike extra fries and soda, a
beefed-up roof provides additional protection
from its mortal enemies – careless
tradesmen, chemicals, animal fats, and UV
exposure. When the numbers are added up,
the supersized roof is clearly the greater
Return on Investment (ROI)
A basic math calculation can be used to
determine ROI in roofing. Simply divide the
cost per square foot by the projected length
of service, and the results are a no-brainer.
This equation shows that the increased
installed cost of thicker membrane actually
saves the building owner money over the
projected life of the roof.
Sandra Gray, RRC, roof consultant and
president of the Moriarty Corporation, with
offices in Texas and Connecticut, is a leading
proponent of using thicker roofing materials.
“If I had my choice, I would specify the
heavier 75-mil membrane every time,” said
Gray. “If the owner intends to keep the
building for an extended period of time, we
tend to specify a thicker material to minimize
life cycle costs.”
This same logic can easily be applied to
the remainder of the assembly. Figure 1
compares the average installed cost per
square foot of a 30-, 20-, and 15-year fully
adhered single-ply system. The 30-year system
is based upon one manufacturer’s1 30-
year warranted EPDM specification that
calls for 90-mil EPDM, cover board, and
prefabricated, ES-1 certified metal edging,
among other design enhancements. Even
with the enhancements, the 30-year system
more than pays for itself with additional
service life. In the spirit of supersizing, this
30-year system also features increased warranty
protection for higher wind uplift, hail
up to two inches in diameter, and accidental
puncture. That’s even better than getting
a free hot apple pie with your value meal!
Save Green While Building Green
The numbers are clearly favorable when
projected over the life expectancy2 of the
roof. However, these estimates are based on
12 • I N T E R FA C E MA R C H 2009
a typical roof installation using the ASHRAE
90.1 minimum standard for insulation: R-
20 (in climate zones 2-8). If these equations
were calculated using the PIMA recommendations
of R-25 (zones 2-5) or higher, the
percentage of the cost increase for thicker
membrane relative to the total installed cost
of the roof system would appear even less
significant. In all climate zones, insulation
can aid dramatically in reducing cooling
and heating loads, lowering energy costs,
and reducing pollution and carbon emissions.
In this day and age, it is
hard to imagine specifying a
roof that is destined for a
landfill in approximately 15
years. Seldom do architects or
specifiers design 15-year systems.
The push for these systems
typically rests with
building owners and roofing
contractors, who value-engineer
their roof designs in
order to generate a system
with a low sticker price.
“Frankly, too many people
are looking exclusively at
installed cost,” laments Steve
Chaffee, principal of Chaffee
Industrial Roofing in Rhode
Island. “I can’t tell you how
often I hear superintendents
asking, ‘What do I care? I
won’t even be here in 20
years.’ It can be frustrating.”
This approach is no more
responsible for the planet
than it is for building owners’
bottom lines. Those in the
roofing community are often
puzzled by this conventional
wisdom, or lack thereof,
which does not seem to happen
at any other point
throughout the
building pro cess.
Imagine the impact
and potential fallout
of specifying a 15-
year foun dation or
exterior wall. The
rest of the building
is intended to stay
erect for a very long
time; yet often, the
roof is not. If the
building is designed
to last for decades
or more, it should
have a roof protecting its contents and
inhabitants for that same duration. A 15-
year roof – especially one that is minimally
insulated – is a promissory note to the landfill:
“See you soon!”
Can the Membrane Be Recycled in 15 Years?
Though initiatives are under way for
recycling membranes at the end of their service
lives, the industry as a whole is still in
its infancy. Currently, systems have to be
torn off, packaged, and transported to a
grinder. Postconsumer, recycled content
can be reintroduced into the bottom ply of
thermoplastics and into EPDM sheeting,
but it is more often used in accessories
such as walkway pads. The current reality
is that recycled materials cost significantly
more than virgin raw materials, and it will
remain this way until additional uses for
the recycled materials are identified and
production volumes are increased. Rather
than simply dispose of the material, roofing
contractors are also finding it more expensive
to tear off materials in accordance with
grinder specifications and then ship them to
the nearest recycling facility. Building owners
are very rarely willing to absorb the
additional cost associated with recycling the
aged roofing membrane.
“We’ve already proven that EPDM is
recyclable,” states Scott Long, EPDM product
manager for Carlisle SynTec and member
of the EPDM Roofing Association’s (ERA)
technical committee. “It is a top priority of
ERA and its entire membership to identify
additional viable sources for the ground
material that will provide a more desirable
option than landfills.”
Figure 1
MA R C H 2009 I N T E R FA C E • 1 3
A good life cycle analysis
program such as Roof$ense or
the U.S. Department of Energy’s
Cool Roof Calculator can project
comparative life cycle costs for
different membrane
thicknesses, effectively
demonstrate the
potential energy savings
realized with additional
insulation, and
calculate the carbon
footprint benefit of
reduced energy
consumption. Such
tools can help building
owners understand the
tremendous payback of
a more sustainable
roofing assembly.
Clearly, recycling is a high priority for
most roofing manufacturers, but it is
impossible to speculate where the industry
will be in 15 years. From an environmental
standpoint, manufacturing materials consumes
energy, but the difference between
manufacturing thinner versus thicker
membranes is minuscule, and materials
still have to be transported to the job site.
The environmentally responsible choice is
not to wait to do it all over again in 15 years
in the hope that recycling technology will
have advanced accordingly.
Thicker Membrane Offers Increased Puncture
Unlike choosing the varying grades of
gasoline at the pump, which offer the consumer
similar performance at different
prices, with the buyer returning a week
later for another fill-up, regardless of grade,
there are several benefits to choosing a premium
or ultragrade roofing system. With a
little common sense, it is easy to realize that
thicker material will
be more puncture
resistant than thinner
Sources of puncture on a roof can
vary, but the most common are
abuse by other construction
trades and foreign objects being
dropped by maintenance personnel
(Figure 2). Thicker materials
will not resist all of these inappropriate
actions, but they can significantly
minimize the potential
damage. Laboratory testing shows
a 50 percent increase in puncture
resistance from a 45-mil-thick
membrane to an 80-mil-thick TPO
membrane (Figure 3).
“We’ve done a lot of roofs in
Chicago-town, and usually when
a leak occurs, it’s because somebody
dropped a tool and punctured
the membrane,” says Gray.
“We specify a lot of 75-mil [reinforced
EPDM], especially when
there is a lot of mechanical equipment,
because we believe that it
offers much more puncture resistance.”
Mother Nature takes her shots
at roofing materials, too. Reports
of TPO and EPDM roofing systems surviving
substantial hailstorms are common, and
simulated hail testing over a variety of substrates
and temperatures showed membranes
60-mil or greater displaying excellent
resistance to damage. In fact, a recent
laboratory study conducted by Jim D.
Koontz and Associates Inc. (JDK), Hobbs,
NM, shows that both new and aged nonreinforced
EPDM roof assemblies offer a high
Figure 2 – Debris left by maintenance crews for various rooftop mechanical equipment increase the
risk of a puncture.
Figure 3
Figure 4 – Three-inch hailstone impacting EPDM membrane, tested
over OSB. To obtain a copy of the full report on Koontz’s research,
visit (Photo courtesy of Jim D. Koontz and
Associates Inc.)
14 • I N T E R FA C E MA R C H 2009
degree of hail resistance over a variety of
roofing substrates. Of the 81 60-mil, nonreinforced
EPDM targets installed over polyiso,
wood fiber, plywood, and OSB board, 76
EPDM roof assemblies retained their waterproofing
integrity when impacted by hail up
to three inches in diameter.
Thicker TPO Contains More Sunscreen
Popular in warm, southern climates due
to its high reflectivity, TPO membrane is
enhanced with a weathering package that
protects the integrity of the sheet and prolongs
its service life. As the sun beats down
onto a rooftop that is waterproofed with
TPO membrane, the weathering package
contained in the TPO formulation will protect
the surface from degradation caused by
exposure to UV rays. As the weathering
package on the surface of the membrane is
depleted, reserves within the remainder of
the membrane will continue migrating
upward (Figure 5). The thicker the membrane,
the greater the weathering package
and the longer the surface will retain its
smooth, glossy appearance. A common
term for this phenomenon is “the reservoir
To combat the negative effect of the UV
rays associated with exposure to the sun –
particularly for buildings in hot, southern
climates – TPO manufacturers offer a variety
of membrane thicknesses ranging from
45 mils up to 80 mils. Because it is thicker,
the 80-mil membrane inherently features
more weathering package than a 45-mil
membrane, thus providing a potentially
longer service life.
“The reservoir effect on a thermoplastic
membrane can be compared to sunscreen,
which features SPF values ranging from two
to 50,” comments Randy Ober, thermoplastic
product manager for Carlisle SynTec.
“Sunscreen with an SPF value of two is a
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MA R C H 2009 I N T E R FA C E • 1 5
Figure 5
good sunscreen, but it will not protect your
skin for the same duration as a sunscreen
with an SPF value of 50. This is especially
important in climates that experience high
levels of radiation from the sun. For example,
while an SPF value of 15 may be fine in
Bangor, Maine, that same level of protection
may not be adequate in Phoenix, Arizona.”
Therefore, a thicker TPO membrane will
offer longer protection against the dangers
of solar UV rays. This is not to say that thinner
TPO membranes are not a solid investment;
however, predictably, their weathering
package will dissipate more quickly
than that of a thicker membrane if they are
exposed to excessive solar UV rays.
What a Roof Wants to Be When It Grows Up
In the past, a rooftop was intended to
keep the building dry. Advancements in the
green building movement have revealed that
a roofing system can save significantly on
energy costs with the addition of insulation
and the use of reflective roofing in warm
southern climates. The future of roofing
now looks even more varied. Cities and
municipalities are offering incentives for –
and in some cases, mandating – the use of
vegetative roof systems. Most vegetated
roofing specifications require a minimum of
60-mil membrane and recommend even
thicker membranes. Since roof garden system
costs can soar to over $30 per square
foot, the membrane cost on a garden roof is
even less significant than the illustrations
While energy-saving roofs are the trend
today, energy-producing roofs are inevitably
where the industry is headed. As roofmounted
photovoltaic (PV) solar systems
become more popular, the issues of puncture
and traffic resistance become even
more serious. PV systems will require regular
maintenance and inspections, which will
increase the chances of damage being
caused by traffic and by tools dropped on
the roof. Given that the cost of PV systems
can reach $40-$50 per square foot, property
owners should specify extra protection
for their roofing investment to ensure that
their PV systems are not prematurely or frequently
taken out of service while the
underlying roof is repaired. They will need
to understand that the extra cost of a thicker
membrane, whether a 90-mil EPDM or
an 80-mil TPO, pales in comparison to the
expense of prematurely replacing the roof
membrane below a PV system.
Sandy Gray was quick to point out that
the Moriarty Corporation has many rooftops
throughout the country with aged 45-mil
EPDM roofs. “We do like EPDM because it is
not deteriorated by UV, and we can extend
its service life by restriping the seams and
flashings. Most of these roofs make it well
past 15 years, some as long as 22 years,
before needing major service.” This is
admirable performance by any measure,
but Gray went on to state that she will continue
to specify thicker materials. “I think
it’s reasonable to expect 30 years and
beyond from a roof.”
1. Based on a Carlisle SynTec 30-year
Sure-Seal® EPDM system. Other
manufacturer specifications may
2. Life expectancy refers to the warranted
term for coverage of the roof
system. In many cases, the roof will
last beyond the warranty term.
Rob Reale has over 15 years of experience in the construction
industry, having started as a laborer framing houses in New
England in the early 1990s. Having earned a bachelor’s
degree in visual communications from the Art Institute of Fort
Lauderdale, he went on to become a partner in Brand Identity
Group in Newton, MA, which specialized in both the commercial
roofing and aerospace industries. Reale now serves as
communications chair for the EPDM Roofing Association and
is manager of Carlisle Creative Services.
Rob Reale
16 • I N T E R FA C E MA R C H 2009
When the California Occupational Safety and Health
Standards Board formally adopted Section 1530.1 of the
Construction Safety Orders, it exempted rooftop operations from
the “silica dust regulation.” Breathing of silica dust, created when
power tools or equipment are used to cut, grind, core, and drill
concrete or masonry, has been linked with silicosis, lung cancer,
chronic obstructive pulmonary disorder, and diminished lung function.
The new regulation generally requires the use of a dust reduction
system, such as application of water or exhaust ventilation,
when power tools are used with concrete or masonry materials.
The roofing industry argued that use of wet saws, vacuum
systems, and other methods of reducing dust on the roof would
only exacerbate the danger for roofers on sloped-roof surfaces.
The California Professional Association of Specialty Contractors
(CalPASC) and Roofers Local Union 81 convinced the standards
board to include, “A dust reduction system is not required for
rooftop operations with roofing tile, roofing pavers, or similar
materials.” If such activities take place on the ground, the regulation
still applies, however.
At the same time that roofing contractors are permitted to drycut
silica-containing materials on sloped-roof surfaces, they are
required either to make sure that employee exposures to crystalline
silica dust are below the permissible exposure limit (PEL)
specified in 8 CCR 5155 or to otherwise supply respirators.
Employers must also train their workers on the possible health
hazards of breathing silica dust.
The exemption will disappear as soon as dust reduction systems
are developed that can be safely used on sloped roofs.
California’s law is believed to be the first safety regulation in
the country to address construction worker health in regards to
silica dust.
— Western Roofing