Reflections On Built-Up And Bituminous Roofing How Energy Regulations Requiring Reflectivity Affect Traditionally Non-Reflective Options

May 15, 2006

Bituminous systems have a long and
proven history of waterproofing performance
but have recently had to address
increasing performance-based requirements
imposed to conserve energy and protect
the environment. These requirements
typically revolve around minimum values
for reflectivity and emissivity to keep heat
off the roof and thereby reduce the cooling
load in the building. Traditionally, asphaltic
systems have had a layer of granules, gravel,
or coating to protect the asphalt from the
damaging effects of heat and ultraviolet
radiation. These effects may cause the
asphalt to more rapidly give up its oils,
which accelerates the
aging process. These
surfacing layers were
designed solely for protecting
the asphalt, and
therefore – with the
exception of coating –
were at a severe disadvantage
when programs
and legislation geared
toward reflectivity and
emissivity were enacted.
In what started as
“composition roofing” in
1845, Samuel Warren
devised a system comprised
of pine tar
applied over a substrate
of paper. The paper
reinforcement provided
a base for the waterproofing
pine tar and presumably introduced
the concept of laps to the low-slope
roof. The final step of broadcasting sand
over the surface to protect the pine tar layer
and add more durability completed this
early roof assembly.
Years later, coal tar made its way onto
the roof, replacing pine tar as the waterproof
layer of choice, with gravel becoming
the chosen protection layer. By 1880, natural
asphalt was introduced onto the roof
and asphalt and asphaltic systems have
remained a prominent waterproofing material
to this day.
Today’s bituminous membranes are
produced with refined asphalt and have
been improved with reinforcements consisting
of fiberglass, polyester, or a combination
of the two. With the introduction of polymer
modifiers such as SBS (styrene-butadienestyrene)
and APP (atactic polypropylene),
the application methods and physical properties
have benefited. These modifiers extended
the useful temperature range of
asphalt and expanded the application
methods. Torchable and self-adhered membranes
join traditional hot mopping and
cold adhesive as accepted application methods.
Polymer modifiers have helped ensure
that elongation and recovery are now
viewed as valuable properties, much as that
of tensile strength. With many options
Traditional BUR installation methods work well for new factory-coated cap sheets.
OC T O B E R 2006 I N T E R FA C E • 1 3
available and a proven history of performance
by asphaltic membranes today, it is
clear why they hold such a prominent position
in the modern roofing market.
Modern Roofing Market
Today’s roofing market is segmented as
shown in Figure 1. EPDM, TPO, and PVC
combine for a 38% share of the national
roofing market as what are commonly
referred to as “single plies.” This description
refers to the fact that these membranes are
typically put down as the primary waterproofing
for the roof in just one layer or ply.
Though relatively new to the market when
compared to bituminous membranes, these
single-ply systems have quickly proven worthy
of merit as demonstrated by their market
share and recent growth curve.
Bituminous systems are comprised of
BUR, SBS, and APP, and still command the
prominent part of the roofing market with a
48% share. Of this bituminous market
share, BUR has the majority stakehold at
19%. It is widely believed that a multiplelayer
roof fosters a more forgiving method of
application, as deviations in the application
of a single layer may not compromise the
waterproofing of subsequent layers. Therefore,
it is seen as a more “bullet-proof” roof,
and that is why it continues to hold a
prominent market share and enjoys a fervent
following by those who believe BUR to
be the best roofing system available.
California is an excellent example of a
proven BUR market. A behemoth of an
economy, it ranks seventh in the world in
Gross Domestic Product (GDP) if individual
states were compared to the countries of
the world. California’s GDP is slightly less
than China but has an economic capacity
greater than Spain, South Korea, Mexico,
and India.1 It is the largest economy in the
United States and therefore commands a
large portion – if not the majority – of almost
any national product segment. The roofing
market in California alone represents 12%
of the entire United States market, and its
system of choice is built-up roofing. This
system has a solid history in California as
the state’s temperate climate, combined
with the relatively consistent and plentiful
amount of labor, give BUR quite an advantage
over other roofing systems. BUR has
therefore claimed 45% of the roofing market
in California,2 where trends in energy and
conservation often get their start.
Nationally, the trend toward energy conservation
has been growing. The oil embargo
of the 1970s started the conservation
efforts and brought to our consciousness
the need to conserve resources. But only
recently have consistently high energy costs
forced us to examine how we use, conserve,
and save energy in all of its forms. This has
been exacerbated by the rising price of oil
as the energy we use for transportation,
heating, air conditioning, and manufacturing
has all been affected. Key phrases and
words such as “urban heat island,” “solar
reflective index,” “reflectivity,” and “emissivity”
have become commonplace in our
everyday dealings as roofing professionals.
Realizing the significant contribution
roofs make to the overall footprint of a
changing and developing municipality, programs
such as Energy Star® and LEED™
(Leadership in Energy & Environmental
Design) have been created to facilitate the
movement to a more energy-conscious
building envelope and roof. Mandates and
regulations have also been created by various
states and municipalities to promote
energy conservation with emphasis on the
Figure 1.
14 • I N T E R FA C E OC T O B E R 2006
Early days of composition roofing.
roof as a means to control some of the engineered
environments within. The Chicago
Energy Code is one such regulation that is
starting to direct the roofing habits of that
city and its surrounding areas, but the
largest single regulation driving mandated
energy savings is Title 24 in California.
Energy Conscious
Title 24 went into effect in California on
October 1, 2005. While it was brought
about by the rolling blackouts that hit California
in 2003, the state has been actively
pursuing energy conservation since the
Warren Alquist Act in 1978. Since that time,
California has remained fairly constant in
its annual energy consumption per capita
at about 7,000 kilowatt hours (KWh).
Meanwhile, the rest of the country has gone
from a per capita usage of 8,000 KWh to
12,000 KWh, representing a 50% increase
in less than 20 years with no sign of energy
Leading the country in energy conservation
efforts, California set out to save its
energy by setting mandates for the efficiency
of a building. In the creation of Title 24,
California would enact a Building Standards
Code consisting of 11 parts, each focused
on optimizing the building. Part 6 of
Title 24 is defined as the “Energy Code” and
was created as a building envelope conservation
effort that assumed a certain size
building could be optimized to stay within
an “energy budget.” This “energy budget” is
based on a computer simulation of the
building’s one-year energy use. Low-slope
roofing (defined as having a slope less than
2:12) plays a predominant part in achieving
this budget.
As previous studies of the urban heat
island effect can attest, lighter-colored roofing
surfaces serve to reflect the sun’s rays
and therefore keep the surface of the roof
cooler. This, in turn, reduces the solar load
and heat transformation through the roof,
thereby reducing the energy consumption
load on the local municipality. The creators
of Title 24, Part 6, took this into account,
setting limits for both reflectivity and emissivity
in the hopes of reducing the peak load
on the energy infrastructure and thereby
reducing the need for new power plants.
Mandating a certain reflectivity made
sense, as the heat energy from light would
be reflected away from the surface and keep
OC T O B E R 2006 I N T E R FA C E • 1 5
Right: California economy in relation
to economies of countries worldwide.
the surface cooler.
Emissivity would also
play a key role in the
code as both were regulated
for minimum
requirements. Emissivity
is the ability of an
object to give up heat. A
high reflectivity does
not ensure a high emissivity.
A very good
example is a piece of
metal left in the hot
sun. While it may be
very shiny and very
reflective, if left in the
sun for very long, it
becomes very warm to the touch and potentially
very hot. It would not be very emissive
in nature, explaining why no aluminum
coatings to date (to the author’s knowledge)
meets the requirements of Title 24.
With the goal of driving energy savings
and avoiding capital expenditures for added
energy infrastructure, the required reflectivity
was set at .70 and the emissivity set at
.75 to comply with Title 24. It was a great
plan that hit the California roofing market
with a resounding wake-up call.
Bituminous systems traditionally have
not had the advantage of single-ply systems
in terms of their color variation, particularly
when considering the light-colored single
plies, which are very reflective and emissive
by their nature. Additionally, smoother surfaces
tend toward better reflectivity values.
The granulated surfaces of BUR cap sheets
therefore act as an impediment to reflectivity,
meaning smoother is better. Since builtup
roofing (BUR) commands 45%4 of the
roofing market, what would become of
California’s most prized membrane?
The Challenge
When considering the desired reflectivity
obtained from Title 24 legislation, traditional
asphaltic-based systems were at a
significant disadvantage. BUR cap sheets
covered with “white” granules would typically
only achieve a 30% reflectivity reading,
5 due in large part to the coverage of the
granules and therefore the ability of the
reflectometer to see the asphalt background.
The jagged surfacing of the granule
coating also hampered the existing surface
from meeting Title 24 compliance. These
factors made for a discontinuous “white”
coating, according to the reflectometer, and
resulted in low reflectivity readings. Even
going to “super-bright” granules would not
alleviate this problem, as it was inherent in
the topography of the granules and
appeared to dampen the future of built-up
roofing in its largest market. Solutions outside
bituminous membranes already existed,
and it was anticipated that Title 24
would perpetuate these solutions and grow
their markets.
Coating the surface was considered to
be the only viable solution for the BUR market.
The creators of Title 24 had anticipated
this by legislating a minimum 20-mil thickness
on any field-coated application. The
thickness of the coating was intended to
provide the required reflectivity regardless
of the uniformity of the substrate. However,
a 20-mil minimum requirement almost
assured a two-phase application process, as
it can be virtually impossible to apply a
sound coating of 20 mils in only one pass.
Additionally, manufacturers often require a
base and top coat be applied as good roofing
Realizing this two-coat process would
most assuredly add cost to a BUR installation
and put this system at a disadvantage
versus other membrane options, manufacturers
quickly went to work to create a solution
that would keep built-up roofing a
viable and cost-effective solution in
16 • I N T E R FA C E OC T O B E R 2006
cap sheet on
Dublin, CA.
Factory-coated BUR cap sheet on Concord Center office building, Concord, CA.
The Solutions
Factory-applied coating became a primary
emphasis, as it would provide the
advantages of controlling the coating thickness
and the curing process, and ultimately
save the additional labor step of postcoating
on the roof. If all of these points
were to come to fruition, it became clear
that BUR would then be able to compete (if
not enjoy a cost advantage) compared to
other membrane options.
A seemingly good solution would be to
coat the sheet after it had been processed
through the manufacturing line. This offline
process would involve taking finished
rolls and unrolling them to apply a Title 24-
compliant coating. Once dry, the membranes
would be rolled again, labeled, packaged,
and sent out into the field. In practice,
this process is very difficult to control, as
ensuring correct coating thickness is difficult
and air-drying usually takes an inordinate
amount of time (sometimes days).
Additionally, foreign matter (debris, dirt,
etc.) can become embedded into the coating
before the drying process is complete.
In-line processes would therefore
appear to be more desirable if a quality
product could be achieved. Creating a quality
product involves controlling many parameters,
including: coating chemistry, coating
uniformity, coating thickness, and cure.
Manufacturers must test a sample of the
finished product with the CRRC (Cool Roof
Rating Council) to achieve values to meet
Title 24, and they must also ensure that the
quality produced on the line conforms to
those standards.
Drying time is a major obstacle to quality
that must be overcome with an in-line
coating process. BUR lines often run ply
felts at around 1,000 ft/min, and cap
sheets typically run around 300 ft/min.
This rate of speed can certainly bolster production
numbers but means that incorporating
new technology into a manufacturing
process can often be quite a challenge. For
example, the time from application of the
asphalt to the virgin reinforcing mat for a
cap sheet, to when a finished roll is produced,
is usually measured in a matter of
minutes. If a manufacturer were to consider
applying a coating on-line somewhere in
the process (presumably after the asphalt is
applied), there would be only minutes for
this coating to dry. Knowing that the sheets
serpentine their way (and will contact the
top and bottom surfaces numerous times
on rolls) through cooling sections of a
machine to try to cool the sheet before it is
wound, this would appear to be quite a
daunting task. For manufacturers with the
means, modified bitumen manufacturing
equipment would seem to be an option to
consider, since modified lines usually run
slower (about 150 to 200 ft/min). However,
modified cap sheets are usually much
thicker than BUR cap sheets, and therefore
inherently have their own difficulties with
coating, including additional mass to cool
and the increased amount of asphaltic oils
that must be controlled and kept from discoloring
the newly applied coating.
Though coating a modified bitumen
sheet is achievable, the thickness adds a
degree of difficulty not found in BUR; it
essentially becomes a question of dealing
with the BUR speed or modified thickness.
Because it is thinner, the BUR cap sheet
provides an excellent substrate if the right
combination of coating chemistry, application
method, curing, and conveyance can be
found that works with the limited amount of
time available in the manufacturing
process. The coated BUR cap sheet would
have a clear advantage, assuming that the
solution met the specifications of Title 24
and industry standards. Additionally, the
product cannot deviate too much from standard
products in order to gain the trust of
the roofing industry.
Few products meeting these criteria
were available when Title 24 became law on
October 1, 2005, but the offerings have
grown steadily since. One such product is a
BUR cap sheet that has provided many
lessons on coating application and field performance
during its development. This new
product has many innovative features in
Typical built-up roofing manufacturing process.
Infrared Roof Moisture Scans
High resolution short-wave FLIR Thermacam for accurate
scans on reflective surfaces.
Survey results marked on the roof surface and verified. Full
reports with CAD drawings on hard copy or via e-mail.
Infrared Inspections, Inc. 1-800-543-2279
OC T O B E R 2006 I N T E R FA C E • 1 7
the way it is manufactured and applied,
which has the potential of pushing the
industry toward preserving the built-up
market in California.
A primary innovation in the product was
going to a finer granule. Standard roofing
granules are a designated size and are
found on most granulated asphaltic cap
sheets. This cap sheet utilized granules that
were sifted to a smaller size but provided
the same protective surface trusted by the
roofing community. The smaller granules
not only allowed for a smoother surface on
which to apply the coating but, according to
the ASTM scrub test, also added an unforeseen
benefit of greatly increasing the granule
In order to compete with field-applied
coatings and ensure a durable surface, the
solids content of the in-line coating was
greatly increased. Field application of a
coating with such high solids would be virtually
impossible. Additionally, the process
inside the plant ran better at high speeds.
The sheet was able to maintain its heat
through the application process and the
energy used to dry the coating could be utilized
in drying, not in re-heating the sheet.
Finally, performance on the roof was
evaluated. The new BUR cap sheet performed
very well in all accelerated testing
and proved both durable and aesthetically
pleasing when installed. This solution
proved that the bituminous industry could
be both innovative and adaptive as it works
toward preserving the market share for
asphaltic systems in California.
Today there are a variety of other
options available to address Title 24 and
keep the built-up roofing system as a viable
option. From a hybrid system consisting of
modified plies with a compliant BUR cap
sheet to a traditional BUR system with a
BUR cap sheet that is also compliant upon
installation, BUR now has the products it
needs to compete for the low-slope roofs of
With the efforts of many manufacturers
and through the valuable input from those
who specify asphaltic systems, BUR solutions
for Title 24 are now readily available.
As energy conservation regulations and programs
spread across the country and
become more prevalent and numerous, it is
expected that what was learned in
California will be a foundation for continuing
to keep asphaltic systems relevant and
a viable option when considering properties
such as reflectivity and emissivity.
BUR has always been a solid and reliable
waterproofing system, but the system
as a whole now has more options to appeal
to those looking for an energy-conscious,
redundant system. These solutions allow
built-up roofing applicators and specifiers
to continue to utilize the membrane system
they feel will give them the best roof possible.
1 – “Comparison
Between US States and Countries’
Nominal Gross Domestic Products.”
2 2005 ARMA and industry data.
3 Lawrence Berkeley Lab data.
4 Johns Manville reflectometer testing
5 Ibid.
18 • I N T E R FA C E OC T O B E R 2006
T.J. Stock is the western region application engineer in
charge of the group supporting roof consultants, architects,
and other specifiers in the western half of North America for
Johns Manville. After five years installing can plants internationally,
T.J. joined Johns Manville in 1998 as a project engineer
working to install new roofing membrane and insulations
plants in various locations throughout North America,
including Macon, Georgia, and Fernley, Nevada. From there,
he was promoted into the New Product Development Group,
becoming a Six Sigma Black Belt while helping to develop and launch new products
such as CleanBond® Self-Adhering SBS, Invinsa® Roof Board, and GlasKap CR®. He
was then promoted into the Application Systems Group to lead the western region in
support of the specifying community for application inquiries regarding building science,
rooftop design, code and regulation compliance, and product and systems specification.
Thomas J. Stock, CDT
According to a recent publication (NIOSH No. 2006-110) by the National Institute for Occupational Safety
and Health (NIOSH), respiration of silica by roofing professionals has only been recognized as a health hazard
recently. NIOSH has measured breathable silica levels up to four times recommended exposure limits when
roofing tiles are cut during the installation process. The cutting generates clouds of silica-containing dust.
Exposure may also occur when blowers or dry sweeping methods are used to clean the roof, creating large, silica-
containing dust clouds. Anyone who inhales dust generated by cutting cement tiles or cleaning the residue
will be exposed to respirable silica, placing them at risk for developing silicosis.
Silicosis is a lung disease caused by breathing dust with silica. The term “respirable silica” is used for silica
particles that are small enough to be inhaled and deposited in the deepest parts of the lung. If workers inhale
too much respirable silica dust, it causes scar tissue to develop in the lungs, resulting in silicosis. Lung damage
may be permanent and disabling and may lead to death. There is no cure for silicosis, but it can be prevented.
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