A series of articles as they appeared in the roofing spec official

,
A series
of articles
as they
appearedin
the roofing spec
official publication
of the National Roofing
ContractorsAssociation
~
official publication of the National Roofing Contractors
Association.
TABLE OF CONTENTS
,
.1-3
~...
Durdan
by James
M.
Donald
Insulation
by
Bernardi
Roof
E.
A.
Insulation
by
Polystrene
Roof
Foam
Expanded
Insulation
Urethane
Rigid
Extruded
Roof
Fibrous GlassRoof Insulation by Edward Mirra, Jr.
Cellular GlassRoof Insulation by Carl Olm
Perlitic
'"'
P. Sheahan.
. .
4-6
...
.7-11
.. .12-14
. . 15-18
Composite Board.Roof Insulation by Paul E. Burgess,Jr. . . . . . . . . . . . . . .
NATIONAl AnoFlNG CONTRACTORS ASsoaATION
One O'Hare Centre
6250 River Road
Rosemont, Illinois 60018
(312) 318-NRCA
...19-20
by Edward Mirra,Jr.
Editor', Note: Edward MirT4, fro is
currently
Section Marketing
Manager, Roof Insulation, for
Owens-Corning Fiberglas Corporation. He receivedhis Bachelor of
Science Degree in Electrical
Engineeringfrom Lehigh Unlwrsity,
and a Masters Degree in Business
Admim:strationfrom the University
of Toledo.
He has been associatedwith OwensCorning Fiberglass since 1962,
during which time he has obtained
experiencein many diverseareas of
the
corporation,
including
Production Management, Sales,
Market Research, and Finance in
addition to Marketing. Mr. Mirra is
a member of the American
Marketing Association, American
Soa'ety of Heating, Refrigerating
and Air Conditioning Engineers.
Professional Engineers Associate.
and the Societyfor the Admncement
of Management.
We are grateful to him for this. our
first in a series of articles on roof
l'nsulation.
INTRODUCTION
Fi~r glass is presumed to have been
discovered some 10.000 Yt'an ago
when nomadic tribesmen built a hot
fire in a bed of sand. The fire melted
the sand. and presumably
a
tribesman poked a stick -into the
molten puddle that appeared. When
he pullecd the stick away the melted
sand formcd a long stringy typc
ROOF INSULATION
fiber. The further he pulled. the
thinner it became until suddenly it
hardened. Little did he realize that
he had formed the first glass fiber.
Now centuries later. there are
numerous products and applications
derived from the discovery of the
glass fiber. One such product is
fibrous glass roof insulation. Today.
architects. owners and contractors
are benefiting from the unique
properties of glass fibers used to
produce fibrous glass roof insulation.
GENERAL DESCIlIPTION
AND USE
Fiber glass roof insulation has two
primary
uses today. First and
foremost is its we as a thermal in.
sulation to retard the flow of heat.
Secondly, it's used as a base for builtup roofing in the construction of
roofing systems for non.~dential
buildings.
As the energy crisis continues to
increase in severity, the insulation
quality of fibrous glass roof in.
sulation is becoming increasingly
imponant in its role of conserving
the nation's vital energy resources, as
well as reducing the operating costs
of businesses and institutions
throughout the United States.
The fine glass fibers from which
roof insulation
is manufactured
provide the very efficient insulating
propenies of the product. However.
a roof insulation product must
exhibit additional properties because
of the complex forces present in a
roofing system.
A
unique
combination
of
properties of fiber glass, not found in
any other material, provides the
characteristics to meet the stringent
requirements of roofing applications.
Properties such as strength: weight
for weight, fiber glass has six times
the breaking strength of steel. Glass
fibers are dimensionally stable and
will not expand with heat or swell
with moisture.
In addition, glass fibers arf::
flexible, inert and fire resistant,
which adds up to an imponant array
of propenies that are panicularly
helpful for the long-range per.
formance of roof insulation and the
entire roofing system.
PRODUCT Df.SCR.IPTION
Fibrous glass roof insulation boards
are composed of glass fibers. The
glass fiber reinforced asphalt and
kraft top surface provides the rough,
impact. resistant mopping surface for
the built-up roofing system.
Roof insulation boards produced
from fibrous glass are available in
"'x4'sizes, as well as4'x 8' sizes,which
result in fewer joints in the roof
system. Fewer joints are purported by
many to provide additional advantages not available with smaller
sized boards, such as less heat leakThe thickness is varied from ~ ,. to
2 v." to achieve the insulation efficiency required as shown in Table
I. Double layer application is also
commonly used to achieve even
greater insulation protection.
TABLE 1:
GLASS nBER. R.OOF
INSULATIONTHER.MAL
VALUE SELECTION GUIDE
CA»nductantt R.ailtantt Thickne.
.11
9.09
2-1/4"
.Ig
7.69
1-7/8"
.15
6.67
1.5/8"
.19
.24
5.26
4.17
1-~/16"
1-1/16"
.27
5.70
15/16"
.56
2.78
5/4"
Fibrous glass roof insulation will
vent vapor through the boards.
Vapor can be vented or free water
pumped out in the event of damage
to the built-up roof, eliminating th~
need to remove the insulation should
it become wet for anyone of many
possible causes. Once the roof insulation has been dried, the original
thermal value is restored.
Fibrous glass roof insulation is
acceptable and approved by Factory
Mutual in accordance with their
published requirements. Similarly, it
is approved
by Underwriters
Laboratories, Inc. for many specific
construction designs.
The majority of decks being
constructed p~ntly
are metal;
therefore, flute span capability of
roof insulation is important. Table 2
provides the fiber glass roof in-
sulation
thickness
with
the
corresponding maximum flute span.
and since alm~t all metal decks have
flute spans of 21,i" or less. fibrous
roof insulation can meet practically
all of the metal deck flute span
requirements.
TABLE2:
MAXIMUM
FLUTE SPAN
FIBER GLASS
ROOF INSULATION
Thicknesa
Inches
Max Flute
Span
Inches
5/4"
15/16"
1-1/16"
1.5/16"
1-5/8"
2-112"
2-518"
S.l 12"
4"
I-SI."
WIDE FLUTE
ROOF INSULATION
Max
Thicknea
Inchea
5/4"
15/16"
1-1/16"
1-5/16"
Flute
Span
Inchea
2-1/2"
2-7/8"
5-1/4"
4-1/4"
HOW FIBROUS
--
-
GLASS ROOF INSULATION
IS MANUFACTURED
The first step in the manufacturing
process of gla~ fiber insulation is to
melt sand. li~one.
soda ash and
other ingredients at temperatures of
25000 Fahrenheit. While the glass is
a molten liquid. it flows through tiny
holes that shape it into fi~n finer
than human hair. Once the fiber
gla~ is formed it is spun into light
fluffy material which is than com.
pressed into a rigid insulation. Th~
insulation then has the reinforced
cover applied. after which it is cut to
size and packaged.
A schematic description of the
process is shown. but only personal
observation of this manufacturing
operation can vividly depict how far
glass fiber technology has progressed
since the tribesmen first discovered
the phenomenon 10.000 years ago.
APPLICATION
OF FIBROUS
GLASS ROOF INSULATION
Fibrous glass roof insulation can be
installed using hot steep asphalt. cold
adhesive or mechanical fasteners
depending upon the specific job and
its requirements. For metal decks
that are Factory Mutual Class I or
classified
as an Underwriters
Laboratories roof deck construction.
their respective specific requirements
must be followed as they relate to
acceptable materials and how they
are installed. One aspect of the
listing of materials for Factory
Mutual Class I requires they passa 60
PSF (Pounds per Square Foot) uplift
test. Although Factory Mutual may
list materials for use with fibrous
glass
roof
insulation.
the
manufacturer's manual should be
checked to see if there are any
restrictions.
Fibrous glass roof insulation can
be installed over the commonly used
vapor retarder systems. For metal
decks. Factory Mutual and Un-
'--"'L'--"'. ~dl
lATCH
.'dl III I d
INGREDIENTS
H
II
II
II
-
III
fJ:~~~~~
."'WEIGH
MIX
qI
~
GLASS MELTIN8
8 REFINING TANK
~
CENTRIFUGE
FORMING
COMPRESS
~'
AND CURE
cr
PACK OR
FABRICATE
derwriters Laboratories guidelines
should be followed as required. The
most common roof insulation application is over a metal deck without
vapor retarder systems. Glass fiber
roof insulation is applied to metal
decks with a 12-15 lbs. per square
mopping of hot steep asphalt. or .7
gallons/square of cold adhesive. or
by the use of mechanical fasteners
being applied one fastener for each 2
sq. ft. of roof insulation. When vapor
retarders are used. .25-.40 gallons of
cold adhesive is applied below the
vapor retarder to adhere it to the
metal deck. and. 7 gal. it applied on
top of the vapor retarded to adhere
the roof insulation. For poured-inplace and other non-nailable surfaces. the deck is normally primed
using 1 gal/square of an asphalt
primer. then the insulation is embedded in a minimum mopping of 30
lbs./square of steep asphalt. Where
joints exist. precaution must be taken
to prevent asphalt drippage. For
nailable surfaces. a mopping surface
must be provided that is adequate to
obtain proper adherence of the
insulation. Possible mopping surfaces might be a base sheet. or a glass
fiber felt. or red resin and No. 15
felt. These added mopping surfaces
are nailed to the deck. and then the
roof insulation is adhered to them by
using a solid mopping of hot steel
asphalt applied 30 lbs./ square.
Where vapor retarders
are
required over the decks. those
commonly
used are acceptable;
however. caution must be exercised
to be certain that the insurance and
code requirements are being met.
...
~=b
CURING OVEN
MANUFACTURING PROCESS
\0
3
r
Editor'" Note: Carl Dim is currently
Business Manager, Architectural
Products Division, for P,.ttsburgh
Corning Corporation. He has been
associated with Pittsburgh Coming
since 1970, haling previouslyworked
for Corning Gla.s.s
Worksin a number
of engineering and manufacturing
positions.
.1.
-
.t:.
"
While with PittsbuTghComi1lg, Mr.
Olm has held the positions of Works
Manager at the company's Pori
Allegany, PA, plant, and Man4ger,
Market Planning. He ~ named to
his presentposition, where he directs
all markelling activities of the Architectural Products Division, in
1972.
Mr. Olm was graduated from the
UniverSt"ty of Pittsburgh with a
Bachelor of Science Degree in Industrial Engineering. He is a
member of the Amen'canInstl"tuteof
Industn'al Engineers, the A mencan
Societyof ProfeSSIonal
Salesmen,and
the Resenle Officer's Association.
Weare grateful to Mr. Olm for this,
our second in a sen'esof articles on
roof insulation.
4
INTRODUCTION
Since the beginning of time. man has
instinctively known that water poses
the greatest threat to his environment.
For countless centuries, man used
materials provided by natu~
to
insulate himself from water, both
liquid and vapor. He used leaves,
wood, and mud. Later, he experimented by using combinations of
those natural insulators.
He found that if he kept dry, he
was warmer. And, he found that
keeping water from coming through
the roof was the key to proper in.
sulation. For, without a waterproof
roof, it would not be long before he
was left with little protection from
the heat and cold and wind and sun.
We see the same principle
in
insulation today. A wool jacket. for
instance, keeps us warm on a cold
day until it gets wet, then it 1<MeS
its
insulating ability.
If we rub our
finger on the inside of a "waterproof'
tent when it's raining outside, we rob
the tent of its insulating efficiency by
permitting moisture to enter.
We know now that it is important
to protect the deck of our roof from
water. The insulation we choose for
our roof should insulate and protect
the roof membrane, preventing the
elements from entering the building.
DESCRIPTION
CELLULAR
OF
GLASS
The manufacturing
process for
cellular glass insulation consists of
combining crushed glass. which has a
very closely controlled
chemical
composition and physical pro~nies.
with a c~Uulating ag~nt. This
mixture is placed in a mold and
subj~ct~d to a t~mp~ratur~ of approximat~ly 950°F in a fumac~. At
this t~mperatur~. th~ glass turns to a
liquid.
th~ c~llulating
ag~nt
d~composes. and the mass ~xpands
to fiU th~ mold. This r~sults in
millions of closed c~lIs. containing an
in~rt gas. connected to ~ach oth~r to
form an insulating mat~rial that is
imp~rm~abl~.
strong. non-combustibl~. and has a constant insulating ~fficiency.
r'"
CELLULAR
GLASS AS A
ROOF INSULATOR
The function of the insulation in a
roof system is to resist the passage of
heat and. to do so, it should also
resist the passage of water in liquid
and vapor form. The insulation must
provide a strong and stable base for
the membrane
and it must be
compatible with. and act in concen
with. other materials in the roof
system.
As a roof insulator, cellular glass
insulation has advantages because it
is:
Impermeable-ASTM
Test C -'55
ratrs cellular glass insulation as Zero
Perm-In. That means water. either
as a liquid
or vapor. cannot
penetrate the material. Because it is
impermeable.
cellular
glass insulation will not cause blistering or
wrinkling of the membrane.
A Constant Efficient InsulatorBecause it is impermeable. cellular
glass insulation remains unchanged
from the time it is manufactured;
during shipment. while ~ing in-
~
Ct'l/ular gia.sshas a compressionstrength of overseventons per squarefoot
stalled, and while in service. It's
guaranteed to retain its original
insulating efficiency for 20 years,
Dimensionally
Stable- A low
coefficient of expansion insures that
cellular glass insulation will not
grow, shrink, warp, or buckle, It
does not contribute to those forces
that the membrane must resist to
prevent splitting or wrinkling.
Noncombustible - Cellular
glass
insulation is approved by FM for
Class I Construction and by V.L. for
Construction
Nos. 1 and 2. It
requires no special protection during
storage or application to prevent its
ignition
or to prevent it from
melting. It can't give off any lethal
fumes, of course, because it can't
ignite.
Light Weight-Because
it weighs
only nine pounds per cubic foot, the
materials requires no extra deck or
structural frame construction and is
eastily handled by the roofing
contractor. Its light weight makes it
ideal for reroofing
applications
where the deck and structural frame
will not permit the weight of heavier
types of insulation.
MANUFACTURED IN
THREE FORMS
Cellular
glass insulation
is
manufactured by the Pittsburgh
Corning Corporation. under the
registered brand name Foamglas. in
three forms: flat boards. flat blocks
and tapered blocks.
Pittsburgh Corning was one of the
early advocates of positive roof
drainage and was the pioneer in
tapered
insulation
systems, a
commonly accepted design criteria
today. The Tapered Roof Insulation
System consists of a series of insulation blocks placed in a specific
sequence to form a slope of 1/16",
liS", 1/4" or 1/2" per foot. Each
insulation block is factory tapered,
identified as to its place in the
sequence, and is marked as to the
direction of slope. Most projects can
be designed to achieve a single insulation layer.
Foamglas Board is made in
modules 2' x 4'; in thicknesses from
11,2" through 4"; and 1,2" increments.
Foamglas Flat Blocks come in
thicknesses from 11,2" through 4" (in
1,2" increments). Sizes are 12" x IS"
and IS" x 24".
All three forms of Foamglas insulation can be installed on all deck
surfaces, the most common being
steel, concrete or wood. The insulation is installed using conventional
roofing
practices,
adhesives. fasteners and equipment.
The material is installed solely by the
roofing contractor, thus insuring one
contractor responsibility.
CONCLUSION
With today's soaring costs and in.
creased consumption of energy. it L-;
imperative that roofing contractors.
owners, and designers be fully aware
of the injurious effects water and
water vapor have on the materials
used in roofing systems.
Ignoring
those effects. when
selecting materials. will cause both
excessiveconsumption of energy and
early failure of the roof system.
5
A t,PI.cal TapeTed Foamglas Roof Insulation Systemis being installed
on this metal deck using conventional TOOftngpactices.
Cellular glass is impermeable. Water, either as a liqw'd or wpor,
cannot penetrate the tn4terial.
".. PER FOOT TAPER
~T8~~~~~:TJIO:
H"
I,.
".-"-
=~1;~:2;tIHlH1~~;~Q~bI:1:
-z.'
This illwtration indicates that on a J /S" slope, the tapered blocks are
positioned single-layer JfJr 28 Jeet. Then, the same sequence is repeated
with the addition oJ a J~ -inch thick foam,;las-Board underlayment.
6
(
\
Editor's Note: Donald M. Durdan is techm'calproduct
representative for rigid foam chemicals in the
Polyurethane Division of Mobay Chenucal Corporation,
p"ttsburgh, Pa.
Prior to jol-mng Mobay in January 1975, Durdan was
salesrepresentativewith E. I. DuPont de NemouTSS Co.
and senior industrial sales representative with Exxon
Chemical Co.
Re is a graduate of Bethany College,Bethany, W. Ya.,
where he received a bachelor of sCIencedegree in
chemistry.
Mobay Chemical Corporation
manufactures
isocyanates and polyols, chemicals basic to the
manufacture of urethane foam spray systems and
boardstock products, which are increasa"nglyused to
insulate commen'cal, industrial, and institutional
bUt'ldings, hot oil PIpelines, and storage tanks.
We are grateful to Mr. Durdan for this, our third in a
senes on roof insulation.
0;-,
Introduction
Historically. the great advances in architecture have been
sparked not so much by radical discoveries in new
methods of building. but rather by the evolution of new
kinds of building materials. In time. wood. stone and
metals emerged as the tripod upon which the whole
structure of building technology rested.
In the past couple of decades. however. science has
added a new dimension to these time-tested building
materials. Its ease of adaptability has been astounding
more than just historians. This new dimension comprises
the spectrum of plastic materials - and more specifically
for this article - rigid urethane foam.
Rigid Urethane Foam... What It II
Rigid urethane foam is a synthetic cellular plastic whose
basic ingredients of manufacture are created by man
through chemistry.
Technically speaking.urethane foam is formed by the
Laboratory Demonstration Of Basic Foam Production Process- ThesePhotographs iUustrate the basicfoaming
process,(1) The two u'qu,a chemical componentsare combined, (2) agl°tatedfor thorough blending, (J) pouTedinto a
receptaclewherethefoaming reaction beginsimmediately, , ,
7
ttaction of two liquid chemicals (isocyanates and polyols)
in the presence of certain additives and catalytic agents.
The mixtutt begins to foam instantly and quickly expands to about 50 times its original volume. The foam
completely fills the area, space or cavity to be insulated
and hardens into an air-tight mas. It becomes tack.free
in minutes, and is totally cured in 12 houri. Thereafter,
the foam, one of the most inert of chemical compounds.
is stable and retains its thermal and other resistive
properties alm~t indefinitely. when it has been properly
installed.
Urethane's superior insulating ability derives from the
high concentration of fluorocarbon vapor - more than 95
per cent of the material's volume-generated during the
foaming reaction. The vapor. trapped in the foam's
millions of tiny cells. has ~xtremely low heat conductance
and keeps internal convection to a minimum. The closed
cell structure is only slightly permeable to air and water
vapors.
Rigid urethane foam is not a single material; rather it
is a family of materials with different formulations for
specific applications.
Which Application Method
ToUIe
Urethane insulation can be foamed-in-place at the
building site by pouring or spraying the liquid components. or it can be factory-produced and delivered to
the job site for installation as laminated slab boardstock.
insulated building panels. doors. siding and other
products. The foam-in-place techniques are useful in
insulating roofs, walls and other elementsin new construction or hard-to-reach areas in existing buildings.
Becauseurethane foam is produced from liquid components occupying 1/30 the volume of the expanded
.
. .and (4,'> uparLsa.on
continuesuntil (6) the rise is
completed. Foam is tackjree shortly aftn completIOnof
the rise. The rigid foam it JO times the volume of the
original chemicals, leading to savings in shIpping,
handh'ng costs.
8
PhotomiC1'ogTaph
showsthe netwOTiof closedcells which
gives rigid urethane foam its unusual strength and
superior insulating wlue. There are about 1,000cells in a
one-inch cube.
0
~
material. substantial savings in shipping. inventory and
material handling costs are realized.
Pouring: This is an excellent method for installing a
strong. seamless core of rigid urethane in wall cavities.
The foam fills all angles and comers of any space or
cavity, going under pipes, around comers and into
crevices.
Spraying: Large open surfaces, such as roofs, can be
covered with sprayed-on layers of rigid urethane, using
special gun.type apparatuses. The chemical components
are mixed and atomized as they are sprayed. To attain
the desired thickness, thin layers are sprayed on suc.
cessively. each adhering to the surface below, hardening,
curing and sealing rapidly. Once applied and as soon as
fully cured. the urethane should be properly protected
from fire, moisture, and ultraviolet lights.
-Most of todays polyurethane technology is based on
production and processtechm"quesdevelopedby Mobay
Chemical Corporation and its parent company in West
Germany" Here," energy-saving n"ga"durethane foam
panels for lam'"nated sheathing aPPlications and roof
insulation are belOng
produced and emluated at Mobays
Pilot plant/application development operation in Pittsburgh, Pa"
I').,
'W
Boardstock or Slabstock: This rigid urethane foam is
produced at a factory where it is cut into flat sheetsof
different thicknesses(generally %" to 3 ~ ") and standard
sizes(generally S' x 4' or 4' x S')" Protective coatings,
mastics, paints, or structural or decorative skins are
applied in the manufacturing process. As a roofing
material, it goes down fast and the roofer needs no
adhesivesother than those required for most roof insulating materials. It's easyto cut to fit around drains,
vents, other obstructions; however, bare urethane foam
should not butt against metal chimneys. Factory-made,
laminated board is being increasingly specified as roof
insulation"
Properties and Performance
Characteristics
The roof is a critical area in building design, construction
and perfonnance. A successful roof protects the
building's occupants and contents from the weathersummer and winter. It helps to make heating, ventilating
and air conditioning systemsworkable and economically
feasible.
Good insulation, properly installed, is an essential
factor in helping to insure long-tenD successof the roof
assembly.With a designedk.factor of 0.14 and a high R.
value (7.14), rigid urethane foam insulation provides
excellent thermal resistance.
The properties of urethane roof insulation yield a
number of advantages for roofing contracton, building
ownen, and architects. Some of these include:
-Thermal
Resistance: Makes possible reduction in
size-and cost-of original HVAC equipment and duct
work; lowen HV AC operating costs; conserves energy
expended for heating and cooling; means that a single
layer of insulating material is usually sufficient to achieve
specified R-value-Light Weight: Can reduce the dead load of a roof by
up to 75 percent, leads to savings in installation time and
labor, and has good compressive strength to resist heavy
loads.
-Minimum
Water Absorption: The stable, strong
structure of rigid urethane foam locks out water
penetration.
-Low Water Vapor Permeability:
Rigid urethane
foam has a moisture-permeability rating in the range of
one to three perm-inches, depending on density and
formulation. However, urethane foam is not a vapor
barrier. A separate vapor barrier should be specified in
high humidity situations, where outdoor temperatures
are frequently below freezing and in cold storage plants
where temperatures of 32 OF or lower are standard.
-Dimensional Stability: Even under a wide range of
temperatures (225°F to -4000F) and humidity, rigid
urethane foam does not shrink or expand to form voids or
dead spots which would reduce insulating efficiency-Venatility
of Foams: In addition to being able to
spray-or pour-in-place, urethane board roof insulation
is manufactured in a variety of forms that make the
material acceptable for almost any kind of deck, shape
and situation. In addition to conventional laminated
urethane boardstock of various thicknesses, there are
available for special situations: 1) Composites which
combine urethane with a fire-rated material. such as
perlite board, glass fiber or gypsum board, to make
insulation acceptable for metal deck, Factory Mutual
Class I construction; 2) laminated high-density foams for
use on plazas or load-bearing decks; 3) tapered laminated
board for easy sloping of flat decks; and 4) composite
board of such strength that it serves as a structural, insulated roof deck.
Energy Conservation
Comfort conditioning requirements of modem buildings
mandate the design and construction of roof aaemblies
that make the most effective we of heating. ventilating
and air conditioning systems.
With no doors or windows to consider in the
calculations, the thermal performance of a roof can be
upgraded simply by specifying sufficient roof insulation
to meet energy conservation standards. Figure 1
demonstrates how adding insulation to an uninsulated
roof can bring about a significant reduction in heat
transmission.
A key example of urethane's energy-saving capabilities
is that a 1" thickness of urethane-board roof insulation
supplies the same thermal resistance (R) as 1 *" of glass
fiber, 2 ~" of foam glass or 2 ~" of perlite. Figure 2
9
illustrates how thick these insulating materials must be to
achieve an R- 7 .14 value.
Figure ~ shows how urethane roof insulation and other
insulating materials cut heat lossesin four different types
of roof decks. The figures apply to a roof area of 100,000
sq. ft.; temperature differential is 60°F. Calculations do
not include air film or inside surface still air.
If there are circumstances which demand thinner roofs
or walls, urethane-with
its superior insulating
capability - makes it possible to reduce the thickness of
the insulation component with no 1011 of thermal
resistance. Or. the thermal resistance of an auembly can
be increased without enlarging the size of the member.
Urethane helps to offset the design restrictions imposed
by the fact that most building materials are constant in
thickness and weight.
Urethane and Fire Safety
Urethanes. like all other organic materiala. are combustible. Precautionsmust be taken to insure that good
fire safety practices are observedin design. installation
and storage. wherever urethanes, including those containing flame retardents, are used.
When used over concrete, poured gypsum or tongueand-groovewood roof decks.urethane normally doesnot
alter the fire hazard rating of the building, but it must be
part of a ClassA, B or C assembly.
If urethane foam is specified for a metal roof deck or
for a roof that is subject to fire exposurefrom below. and
underlay of perlite, gypsum board or other fire-rated
material in most casesmust be installed betweenthe deck
and the foam. Recently, an isocyanuratebued material
(modification of the Itandard urethane chemistry) has
been acceptedin Factory Mutual ClassI Construction as
a non-composite material.
Other recommendationson the safe use of urethanes
are contained in "Fire SafetyGuidelines for Useof Rigid
Urethane Foam Insulation in Building Construction, ,.
HIMIf'IEAT l8II
WITH AND WITHOUT
~IGN
~
CONDITIONS: 10,CXXIoq ft, 2" Iw.-gill
-roof d8ok.
rooIng, WF temper.I",.
dIn_III I) CaIcuIMioI8
do .-
-.cIud8
.. ... « -~
.-~
surface
.Iill ..
-~
~~
.~
ea
I.a
[Ii
=.,-ConcI8d81*
T*R
U""'ot.-
=-~
Cancl8d.:t
TOI8IA
U
0.8
-~~
r
_uno.
°For8lUl8 lOt """'ning
'-I
No ~:
WIII~:
E-w
-'ng
k-.:
~raaf
~
I-.~
U
0..-
o.~
with minIm8/NIl.ion:
x to t
x eo
x.
x
x
Area
lo.cq
-
en.234.
x lo.cq -
81.
8PIIIOx"""", ~
I,".
I;.
FIG. 1
THICKNESSFOREQUIVALENT
THERMALRESISTANCE
published by Urethane Safety Group, The Societyof the
Plastics Industry, Inc.. ~55 Lexington Avenue, New
York. NY 10017.
~
-COt
..
Sprayed-onurethanefoam, when properly instaUed,can
be wed to insulate roof decks. The material is especially
aPPll'cableto hyperbolic paraboloid roofs suchas the one
in this photo, After it hardens. the foam must be coated
to protect it from weathering.
10
0
FIG. 2
COMPARATIVE
ENERGY-SAVING
EFFECTIVENESS
Roof
Constructiop
HeatLoss
Uninsulated
1" Urethane
(R=7.14)
HeatLoss
WithInsulation
1 GlassFiber
1" FoamGlass
H
(R=4.00)
(R=2.86)
1 Perlite
(R= 2.56)
H
Metal Roof Deck.
+ BUR
fR = 0.33)
18,180,OOOBTUH
8O2.800BTUH
2- Poured Gypsum
Deck + BUR
+ Vapor Barrier
(R=1.65)
3.660.000
660,000
+ Vapor
2,400,CXK)
624,000
2" lightweight
Concrete + BUR
2,340,000
618,000
2MWood
+ BUR
Barrier
(R = 2.48)
1,320,OOC
1.425,178
925,925
1,122,000
1,190,478
916,(KK)
1,O8O,(XXt
1,174,168
1.~1.947
(R=2.55)
.If urethane Is used to Insulate a metal roof deck, the insulating system must include a firerated material such as perlite, glass fiber or gypsum board as the base. See page 14.
FIG. J
...
r
.
,;
'"
by A. E. Bernardi
Typical deposit of perlite ore with soil overburden
removed.
12
Perlite ore is a volcanic glassfound in abundancein the
mountainous areas of the West and other areas of the
world. It is extracted from the grip of Mother Earth bya
strip mining process, crushed, screened,and graded for
ultimate expansion into particle sizessuitablefor a varity
of uses.
It has been said that expanded perlite was discovered
by accident when a dissipated and despondent
prospector, while sitting at his camp fire one night, threw
a handful of perlite ore into the fire in a gestureof disgust,
and much to his amazementit popped or expanded.
Whether that is fact or fiction, perlite ore in its natural
state ranges in color from a transparent light gray to a
glossyblack and has a combined water content of two to
six per cent. It is the latter characteristic which causes
perlite ore to expand from four to twen~ times its volume
when subjected to a furnacing temperature of approximately 1700oF. At that temperature, the combined
water vaporizes and the ore expands or "pops" into
countless snowy white to grayish miniscule nonconductive glass spheroids which account for the excellent thermal insulation of expanded perlite.
Typical uses of expanded perlite are as a lightweight
aggregate in concrete, loose fill insulation, plaster
aggregate, pipe insulation, foundry sand additive.
filteraid, and a multiplicity of other applications both
within and outside of the construction industry.
Expanded perlite ore is the principal ingredient in
perlitic roof insulation. An acqueousslurry comprised of
expanded perlite, cellulosic fiber, asphalt and possibly
starch is formulated and deposited in the head box of a
Fourdrinier Machine. From the headbox. it is moved on
to a moving screenwhich forms a wet mat from the slurry
solids. The wet mat is dewatered and subjectedto external heat in an oven or dryer.
As the dry mat exits the dryer, it is sized into pieces
measuring 2' x 4' by a series of gang saws, stacked,
wrapped, and unitized for mechanical handling.
MANUFACTURING PROCESS OF
PERLITIC ROOF INSULATION
Perlite Ore
Fourdrinier Machine
"
,0
I
.
I
"fc
Saws
Crushed Perlite Ore
ExpandedPerlite Ore
The three stagesof processing one ounce of perlite ore
illustrate the volumetric increase upon furnacing.
Perliteroof insulation is designedfor use over nailable,
non-nailable, and steel roof decks. It provides a
dimensionally stable thermally resistant surface for the
applicationof built-up roofing, and it may be applied to a
steel deck with hot or emulsified asphalt, solvent
adhesive, or mechanical fasteners.
The top surfaceof perlitic roof insulation is treated to
minimize bitumen absorption and provide an intimate
bond with built-up roofing. It is light weight, is easyto cut
or contour, has a high resistance to moisture, has no
capillarity and is resistantto compression or indentation
from normal on the job traffic of roofers and the
mechanicalequipment frequently used in the processof
installing a built-up roof.
Perlitic roof insulation is an approved component of
Class I Insulated Steel Deck Construction and several
specific construction desgins as described by Factory
Mutual System and Underwriters Laboratories Inc.
respectively.
It has a flame spread of 25 which is derived in com.
parison with untreated red oak as 100 and asbestos
cement board as 0 during exposure to lire under con-
13
trolled conditions in accordance with Underwriters
Laboratories Inc. Standard Test Method for Fire Hazard
Classification of Building Materials (UL 723).
It is manufactured in compliance with FEDERAL
SPECIFICATION INSULATION BOARD. THERMAL
(MINERAL AGGREGATE) HH-I-529B and in accordance with the U.S. Department of Commerce
"Simpllfied PracticeRecommendationR257-55 Thermal
Conductance Factors for Preformed Above-Deck Roof
Insulation" requiring a thermal conductance "C" of .36
for a nominal 1" thickness.
Although other nominal thicknesses of perlitic roof
insulation have been made available from time to time,
the following representsthose commonly manufactured
with applicable thermal conductance and resistance
values:
Thermal
Thermal
Nominal
Resistance
Conductance
Thk:kness
.48
2.08
3/4"
2.78
.36
1"
4.17
.24
11/2"
.19
5.26
2"
14
Dual layer application of perlitlc roof insulation with
staggeredjoints is customary in those instanceswhere a
thermal resistancevalue exceedingthat achievablewith a
singlelayer applkation is desired ot becauseIt is thought
to reduce heat loss and ridging of the built-up roofing
membrane over the joints.
Perlitic roof insulation is usedextensivelyas a substrate
for polyurethane foam in the production of composite
roof insulationbecauseof Itsfire resistivequality. It is also
frequently used in the field as the Initial layer of roof
insulation over which is then applied a polyurethane or
polystyrene roof insulation with staggeredjoints.
Good roofing practice dictates that roof Insulation of
whatever type should be kept dry before, during, and
after installation, and perlltic roof Insulation is no exception. At the jobslte, It should be stored on risers at
grade level or on the structural deck and covered with
tarpaulins, and no more of It should be installedthan can
be completely covered with built-up roofing the same
day.
...
~
()
Editor'. Note; This article, fifth in our
serieson roof insulation, is presented by
James P. Sheahan, Roofing Industry
Specialist for The Dow Chemical
Company, Midland, Michigan.
Mr. Sheahan graduated from the
Uniuerslty of Toledo In 1953 with a B.S.
in Chemical Engineering. He worked in
the plastics section of Douglas Aircraft
from 1953-55, working with thermoplasticsand reinforced plastics. From
1955 through 1959, he 5ertled as an
auiator in the U.S. Nauy. In 1959, he
joined The Dow Chemical Company,
and has been associated with plastic
foams, primarily extruded polystyrene
foams as related to the construction
market, euer since. He has been particularly concerned with roofing during
the entire period.
Mr. Sheahan has had responsibi/itJes
in technical serulce, research and
deuelopment, market deuelopment,
market research and marketing. In his
present position, he is concerned with
Dow and Industry producls worldwide.
We are Indebted to Jim for his time and
effort in preparing the article that follows.
(Since The Dow Chemical Company
is the sole manufacturer of extruded
expanded polystyrene roof insulation,
the term STYROFOAM brand insulation
appears frequently throughout this article. While our normal publishing policy
is to restrict the use of brand names and
trademarks,
we
feel
thot
the
ci,-
cumstancesIn this case warrant It. This Is
not. of course, on endorsement on the
port of NRCA. but rather a recognition of
the existing market conditions.)
INTRODUCTION
STYROFOAM. RM brand Insulation is
an exbuded, expanded pol~ene,
designed for use as roof insulation. It is
not a new product. The original patents
for expanded polystyrene date back to
1931. The first material designated as
STYROFOAM was produced in the
1940's during World War " for use as a
flotation medium. The lightweight, closed
ceO.water-resistantfoam possessedideal
properties for flotation. In 1948. the first
commercial structure insulated with
STYROFOAM brand insulation was
constructed. It was a low temperature
space warehouse. The traditional material. cork. was replaced with STYROFOAM brand insulation because
the closed ceOcharacteristicdeveloped a
better insulation value requiring less
thickness. and long-term insulating
performancebecauseof the resistanceto
the entranceof water. The rigid structure
allowed finishes to be installed for
a protective surface. These attributes.
coupled with the fact there was a
shortage of cork. provided the first inroad of STYROFOAM brand polystyrene
foam as an insulation material.
Many uses developed over the years
basedon the unique properties inherent
to this material. For non-insulating
purposes.in addition to flotation. the use
of the material in f\oraJ and novelty
end uses Is familiar to most people.
STYROFOAM brand plastic foam has
had much greater use as an insulation.
starting with low temperature space
buildings and spreading to walls and
roofs of commercial buildings. sheathing
for agrkuhural buildings. sheathing for
residential buildings. covering of tanks
"Trademark of The Dow Chemical
Company
IS
and vesselsin the industrial market and usuallyexpandedto a 21b./ cu. ft. density
below grade for building foundations and by castingby batchor continuous process
as an underlayment for highways.
producing large billetsfrom which boards
While there is little confusion in
can be cut. Also, it can be cast and
distinguishing between plastic foam
laminated in a continuous process. The
insulations and the more familiar fibrous process is similar to making a cake,
insulations, there is a tendency to not
where ingredients are mixed and a
recognize the differences between
reaction takes place producing a rigid
various plastic foams. Just as there are
foam with cells filled with a captive gas
differencesin the propertiesof the fibrous producing a very efficientinsulation value
insulations, there are very specific and
rating of K - .16 (R = 6.2). The inmeaningful differences between plastic sulation efficiencytends to decreasewith
foams. Three of the most popular types time, especially when subjected to high
are reviewed for clarification.
moisture conditions. Various skins, such
STYROFOAM brand insulation is as metal foil and roofing felts laminated to
extruded, expandt.d polystyrene. The the foam improve the long-term inextrusion process produces a continuous sulation performance.
flow of material of interconnectingclosed
The different processesand polymers
cells. The process may be considered
produce very different foams. A more
somewhat akin to shaving cream or
detailed explanation of the process to
whipping cream obtained from a
produce STYROFOAM follows to assist
pressurized canister. The polymer is
in understanding how its properties are
expanded about 30 times, providing a
designedfor a particularend use, namely
density of about 2 Ibs./cu. ft. The cells roof insulationare expanded with a gas that is retained.
PROCESS
providing a low insulationvalue rated at a
K of 0.20 BUT in/hr/ft2 /oF at a mean
The raw material, styrene, is made from
temperature of 75°F (resistance- 5.0).
derivatives of coke and crude oil. It is
The insulation value tends to remain
polymerized to form polystyrene. A
constant in usage,even when exposed to
solution of blowing agent in molten
high humidity conditions. The polymer
polystyrene is formed in an extruder
is considered to be hydrophobic, i.e.
under pressureand this solution is forced
water-hating, and works in conjunction
through an orifice into ambient temwith the closed cell structure to provide
perature and pressure. The blowing
long-term water resistant properties.
agent then vaporizes and causes the
The polystyrene is affected by most
polymer to expand. The polymer is
organic solvents and it will bum.
simultaneously expanded and cooled
Molded board or beadboard is also
under such conditions that the polymer
based on polystyrene polymer and is
develops enough strength to maintain
expanded up to 60 times, providing a
dimensional stability at the time of
density of about 1 Ib./cu. ft. Higher
maximum expansion.
densities can also be produced. The
In the first days of production, large
major difference in the production
billetswere formed and cut into lengthsof
process is that small beads are fused or
approximately 9 ft., and stored outdoors
molded together much like in popcorn
for severalweeksto allow equalizationof
balls. The properties are for the most part
the pressurein the cells. After curing, the
dependent on how well the beads are
billets were treated much like lumber and
fused to each other. The cells are tiDed sawed to appropriate board and block
with air, resulting in a K factor of .24 (R
shapes.This processwas modified in the
- 4.2). The insulation value tends to
1950's to extrude a modified billet,
remain constant unlesssubjectedto high
slabbedto size,and cured at an elevated
moisture conditions. Most often, the
temperature to bring about a more rapid
process is batch vs. continuous where
equalization of the air in the cells. In the
large billets are slabbed into boards;
early 1960's, the process was modified
however, molded boards can be
again utilizing a captive blowing agent
produced on a continuous basis. This
system. The new blowing agent immaterial is also affected by organic
proved insulation efficiency, which
originally was K - .36 to .20. Coinsolvents and will burn.
Urethane foam is basedon a different
cidental with this change, boards were
polymer, which is thermo-setting. This
extruded to size, varying from 3/4" to
meansthat'once it is formed, it cannot be
31Ji' in thickness.The boardsare up to 4'
reverted to its original shape as can a
wide and to 9' long. Boards used as roof
polystyrene foam which is thermoinsulation are cut to 2' x 4' and the
plastic. The urethane polymer will burn.
product identified as STYROFOAM RM
but is more resistantto solventsand may
brand insulation.
Boards extruded to sizeprovide a skin~
be used at higher temperatures. It is
16
on the top and bottom surface, improving the strength properties of the
product, particularly the compressive
strength. The final product is a rugged
board that can take abuse during installation and provide long-term performance properties of high insulation
value even when subjected to the
temperature and moisture extremes of
the weather.
PROPERTIES OF STYROFOAM
BRAND INSULATION
It has been over 30 years since
STYROFOAM brand plastic foam was
first considered as an insulation material
because of its predictable long-term
insulation performance. Unanswered
questionsat that time were: whether the
material had sufficient structural integrity
to resist the rigors of construction, a
sufficiently high end use temperature
limitation, and adequate resistance to
combustibility. These questions were
answered in the affirmative. The
properties of STYROFOAM RM have
been tested over the years in the
laboratory and by field experience to
prove the material can be used successfullyin construction by following the
specifications of the manufacturer.
STYROFOAM brand insulation has been
used in many forms in many construction
applications where each property has
beentestedand not found to be wanting.
The following describes the characteristics of various forms of STYROFOAM brand insulation.
WATER RELATED PROPERTIES
The polymer is water-resistantand the
closed cell structure provides a
mechanical barrier to the entrance of
water. Water is the "Achilles Heel" of
most insulations. With some types of
insulations, water degrades the material
to the point of losing its structural
properties. This is of particular importance when the insulation is used as a
base for the built up roof or as the
protection for the built up roof as in the
protected membrane assembly. There
are a number of mechanismsby which
water can affect insulation and many
examples, some with 30 years of history,
demonstrate that STYROFOAM RM
brand insulation is essentiallyunaffected
by water.
Water Absorption 0.55% by Volume
(ASTM 02842.69)
Water absorption is kept to a minimum
because the polystyrene material is
resistant to water, and the closed cell
structure inhibits the entrance of water.
This quality has been demonstrated in
the flotation market where docks and
~
c
~
"CC';",
marinas have been floating high and dry
for decades.
Moisture Vapor Tran.miasion 0.4
Perm-Inch (ASTM C-355-64)
The multi-celled structure and the high
density skin of the roof insulation product
combine to form a product that has a
low vapor transmission. Water is
prevented from entering when the insulation is subjected to vapor pressure
differentials which exist in every construction end use, particularly roofing.
The moisture vapor transmission of
STYROFOAM br-and insulation Is less
than 1 perm which, by rule of thumb, is
considered to be a vapor barTier.
STYROFOAM brand insulation can pick
up water under extreme conditions of
high moisture vapor drive for long time
periods, especiaOy when the vapor
barrier (in applying the built-up roof) is on
the cold side, as it is in conventional
roofing. However, applications in low
temperature space and industrial end
uses have shown the material performs
successfully when exposed to this
condition without a meaningful loss in
insulation value.
Freae/Thaw Cycling
3~ by
Volume Water PIckup After 1000
Cycles (ASTM 666-73)
The integrity of the ceOstructure resists
degradation by freeze/thawing action of
water, which will destroy more rigid
glass-like Insulations. Use over 15 years
in earth insulation applications.such as a
basefor highways, has demonstratedthe
material resists degradation by this
method of attack by water.
Humid Aging
3% Change
In Volume
(Federal Specification H.H.I. 524b)
The hydrophobic qualitiesof the polymer
combined with the closed cell structure
prevent the Ingress of water due to
exposure to hot, humid conditions.
Under conditions of 100% humidity and
140°F, the insulation has the quality to
not only prevent the loss of insulation
value, but to resist change in volume,
therefore maintaining good dimensional
stability. Performance when exposed to
these conditions has been demonstrated
by the use of the material as a base for
roofing, where water hasgained entrance
into the roofing system, and in the
protected membr-aneassemblywhere the
insulation is exposed directly to such
conditions.
Aged Insulation Value 0.20 BTUIn/Hr/Ft2 ;OF at 75°F Meon
(ASTM C-177-71)
The foregoing demonstrates the
material'sresistanceto water pickup This
resistance to water plus the ability to
"";~'
c'
ROOF INSULAT I ON
contain the gas within the closed cell
structure insures a predictable long-term
insulation value.
exposed Is cut in half, thereby redudng
predicted
movement
by one-half.
Further. the size of the insulation board Is
2 ft. x 4 ft., so the total change in
dimension due to temperature change is
limited. Adhering the material to the
strudure impedes movement significantly
because STYROFOAM
brand plastic
foam is not sufficiently strong to overpower the bond of the adhesive.
TEMPERATURE RELATED
PROPERTIES
Polystyrene is a visoelastic material,
which meansIt displaysa broad range of
thermal behavior when heated above
room temperature. The first level of
Interest is the heat distortion point STRENGTH PROPERTIES
{l65°FJ which is diS4..ussed
thoroughly in (Manufacturer's Method)
the next paragraph. At about 240°F it
Tensile Modulus
3,800 psi
can be deformed if a k>adis applied for a
Tensile Strength
90 psi
shoo time, but tends to recover its shape
Compressive
Modulus
2,400
psi
when the load is removed. Above 480°F
Compressive Strength
45 psi
the polymer softensand flows. The flash
The physical properties
of STYignition point is 690°F and self-ignition
ROFOAM brand insulation are lower
occurs at 735°F
(1/4 - 1/10) than most roofing materials.
Also,
the strength properties generally
Heat Distortion Point 165°F
remain
unchanged
by changes in
(Manufacturer'sMethod)
where
most building
The recommended maximum end use temperature
products demonstrate a marked increase
temperature of STYROFOAM tM'and
Insulation is related to its heat distortion in strength properties at cold tempoint. The 165°F is based on exposure peratures.
The tensile strength Is an Important
of the entire board in an oven to a
consideration for long-term performance,
temperaturewhere no physkal change in
shapeis noted. This is a control tn that when combined with the coefficient of
by experiencecan be relilled 10 success- expansion / contraction. These properties
determine the force that could be
ful field experience. For example,
STYROFOAM RM bla~ri insulation can transmitted to adjacent building matbe b:ought directly Into contact with erials, such as a built-up roof instaUed
to the Insulation.
While
asphaltat 325O! by use of a roll coater to directly
STYROFOAM
brand
Insulation
tends
to
apply 10 Ibs/ft of asphalt to its surface.
It can also be brought Into direct contact have a high rate of movement, i.e., strain
with asphalt that has been mopped to a due to temperature change, the force,
deck, becausethe mass of the asphalt is i.e. stress developed, Is low because of its
reduced by flowing to a thin layer, low tensile strength.
While the strength properties are
allowing the material to quickly reduce In
temperature to 250°F. This allows in- considered to be low, the density of the
stallation without mehlng or distorting of product Is maintained in excess of 2 lb. / cu .
the board. Because black roof surfaces ft. for roof insulation. This 8O0ws the
can reach temperatures of 180°F, only material to be used successfully by the
gravel surfacedroofs were spectfledto be construction trades and to perform longinstalled over STYROFOAM RM b:and term by resisting the rigors to which It Is
insulation. While care must be exercised exposed. In particular, the compressive
by the contractor while working with strength Is equal to or better than most
STYROFOAM brand insulation in direct rigid roof insulatk>n boards. Experience
contactwith hot asphalt, techniqueswere has shown It has served well as a support
developed to adhere the insulation to for roofing membranes subjected to roof
various str\Jcturesand to a built up roof traffic and as the base for finishes varying
without deterioration. Because of the from loose stone to concrete pavement.
structural integrity of the STYROFOAM SOLVENT RElATED
RM brand Insulation, when properly PROPERTIES
Installed, the ultimate bond to con- Polysryrene based products can be
struction materials is strong both in dissolved by most organic solvents. The
reaction intensifies with an increase in
tension and shear.
temperature.
When
STYROFOAM
Coefficient of Expansion/Contraction
brand insulation is recommended for use
35 oX106 In/In/oF From -30°F
in direct contact with solvent based
to lsooF (Manufacturer'sMethod)
adhesives, waterproofing
or flashing
The coefficient of expansion/contraction materials, specific directions must be
of plasticfoams is generally higher. 2 to 8 followed. Coal tar pitch can be used with
RM brand insulation
times, than most roofing materials. STYROFOAM
However, as with all insulation materials, where long-term exposure does not
the temperature differential to which it is exceed 100°F.
~7
FIRE RELATED PROPERTIES
Although STYROFOAM brand insulation contains a flame retardant
additive to inhibit accidentalignition from
small fire sources, it is combustible and
may constitute a fire hazard if improperly
used or installed. During shipping,
storage, installationand use, this material
must not be exposed to open flame or
other ignition sources. Consult The Dow
Chemical Company's literature for
specific use instructions.
In testing designed to measure the
resistance of a deck assembly (structure/insulation/built-up roof) to external
fire, including burning brands falling on
the roof, under high wind and varying
slope conditions, the roofs constructed
with STYROFOAM RM brand insulation
as the baseof the buih-up roof and above
the built-up roof in the protected
membrane assemblyqualified for a Class
A rating by Underwriters' Laboratories.
In testing designed to measure the
resistanceof a deck assemblyto internal
fire, the protected membrane assembly
utilizing STYROFOAM brand insulation
qualified for many additional ratings.
Additional information is available from
the testing organizationsinvolved or The
Dow Chemical Company.
APPUCATION IN
ROOFING SYSTEMS
STYROFOAM brand polystyrene foam,
in various forms, was used as a roof
insulation as early as 1948 as the basefor
built-up roofing, and has been used since
1968 in the protected membrane
assembly. It is useful to trace the history
of these two methods of installation to
understand the evolution to the present
system. Through its long history, work
has concentrated on methods of installation that made the insulation with its
limited end use temperature compatible
with normal methods of construction of a
BUR.
Initially, boards cut from large logs
were attached to decks with hot asphalt
or nails. Some form of thermal barrier
was applied over the insulation before
applying the BUR. Materialssuch as 1/2"
thick layer of cement mortar were used
first. Later on fiberboard roof insulation
was mopped and flopped on the foam to
develop a more economicalsystem. This
system is still recommended by various
manufacturers of polystyrene foam. A
later specificationcalled for the first ply of
roofing feh to be nailed directly to the
insulation before applying the hot applied
BUR to provide a more economical yet
heat resistant system.
18
In the late 1950's a roofing product
called ROOFMATE . was introduced.
This wasa foam fully wrapped in a heavy
asphalt kraft laminate paper providing a
roof insulation to which a BUR was
applied directly without added protection
from the hot asphalt. This product was
supercededin the early 60's by a board
extruded to shape with a polystyrene
skin. The use of a captive blowing agent
was introduced a few years later utilizing
the same roofing system as the previous
product. This concept utilized a dry
applied coated base sheet to provide the
themal barrier during construction. The
idea took advantage of the heat during
application to develop an intimate bond
between the built-up roof and the
STYROFOAM brand insulation without
causing degradation. Alternate methods
of mop and flop, flying in or movable felt
layers were also used to apply the first
layer of BUR.
STYROFOAM brand plasticfoam was
marketed as a base for a roof insulation
from the 40's through the 60's. In 1950,
the first protected membrane assembly
was installed using the STYROFOAM
brand insulation as the protection for the
BUR. The systemusesthe inherent water
resistant properties, structural integrity
and long-term insulation value of
STYROFOAM brand insulation in a
designed way. The waterproofing, the
BUR, was placed on the warm side, in
the position of the vapor barrier. Work
continued into the early 60's when a
patent wasgranted. This wasfoUowedby
a number of developmental roofs using
various techniques and finishes which
were evaluated until 1970 when the
systemwas marketed as IRMA (Insulated
Roof Membrane Assembly).
The protected membrane assembly
constructed using STYROFOAM RM
brand insulation is relatively new, but the
basic concept is not. Roof membranes,
particularly BUR's, have been installed
directly on flat structural decks for over
100 years. Many of these had graveled
surfaces. Employing the protected
membrane concept entails placing
STYROFOAM brand insulation on top of
the BUR before the stone is applied. The
result is protection for the membranein a
predictable manner from ultraviolet
radiation, mechanical damage, and
thermal cycling.
The inverted concept gives performance regardless of the type of
waterproofing material used-from the
typical 4-ply built-up roof to built-up
membraneswith fewer plies; membranes
using coal tar pitch, low mek asphalt or
high melt asphalt and with felts based on~
glass,asbestos,or paper. Also a number
of materials such as rubber, vinyl sheet
membranes, or certain liquid applied
membranescan be used. Various finishes
in addition to the stone ballast can be
used to provide decorative or useful
finishes. The key to the successis the
insulation material sandwiched between
the waterproof membraneand the finish.
It must be resistant to degradation
becauseit is subjectedto all elements of
the weather.
The protected membrane concept is
functional for all market areasof roofing:
new roofing, repair roofing and
retrofitting (adding insulation to existing
roof assemblies).In all cases,the owner is
interested in receiving and therefore the
contrartor is interested in delivering
economical systemsthat will perform for
a long time. Today. more important than
ever, this includes energy control along
with water control. Not only must the
system be watertight and require
minimum maintenance, it must control
the flow of energy both in the summer
and in the winter. This meansthe proper
amount and proper type of insulation
must be specified. In the protected
membrane assembly.the materials work
in harmony, i.e., the insulation protects
the membraneand is independent of the
membranefor its long-term performance
capabilities.
While the protected membrane
assembly as used today is wellengineered, it does require a heavier
than normal stone finish, i.e., 10#/ft.2
versus 4# /ft.2. Work is underway
developing ways to reduce the total dead
load to make the system more compatible with existing structures and take
advantageof the economy of lightweight
deck construction for new construction.
~
(
SUMMARY
STYROFOAM brand plastic foam has a
long history as a roof insulation. In the
protected membrane assembly it
provides a mechanism for providing
long-term performance. The proven
insulation value provides economic
advantagesto the owner in this time of
energy shortages and resultant high
costs. The proper amount of insulation
can be specified and enhance the performance of the roofing system. The
protected membrane assembly utilizes
accepted and time-tried roofing systems,
and is compatible with the new waterproofing membranesbeing introduced to
the market. It is made possible by the
unique propertiesof an insulation such as
STYROFOAM brand insulation. . . *
~
by PaulE. Burgea, Jr.
Senior ResearchChemist
Jim Walter ResearchCorp
In these critical times of world-wide
energy shortages, dwindling and Increasingly high cost energy sources, and
Increasedurgency upon the conservation
of energy, no segment of the construction Industry offers more Immediate
relief from this urgent sociological
problem than the Thermal Insulation
Industry.
Thermal Insulations are materials
which offer resistance to or retard the
flow of heat. An efficient thermal Insulation material provides numerous
obstructions to the flow of heat. Generally, these obstructions consist of
voids In Intermeshlngfibers, expanded or
popped non-conductive spheroids, or
Individual gas-containing cells in plastic
or glass foams. These obstructing voids
or cells are sufficiently small that little or
no convective heat transfer occurs and,
therefore, insulating efficiency Is high.
Roof insulation Is a type of thermal Insulation designed for installation on the
uPpenTlost surfaceof a structuralunit as a
means of conserving energy by keeping
the heat In during cold weather and out
during hot weather. Since the roof area
COMPARATIVE
THERMAL
EFFICIENCY
URETHANEFCIAM
(TEMPCHEK)
FIBROUS GLASS
PERLITE BOARD
FIBERBOARD
CELLULAR GLASS
thOck
1"
2"
3"
,eqooit.d IOf .""...18"1
THE~MALRESISTANCE
R.
fF11I
(OF)
CH~
BTU
of single story buildings can represent
85% of the total exposed area, a thermally efficient roof assemblycan provide
perpetual savingsthrough reduced costs
for fuel energy necessary to provide
environmental control for the structure.
There are seven major types of non-
structural roof Insulation materials
currently used. These commonly used
roof insulations are rigid polyurethane
foamboard. perlite board. fiberboard,
glass fiberboard. foamglass, styrofoam.
and composite boards. Comparative
thenna\ efficiencesof the basic types of
insulation materialsare shown in Fig. 1.
Over the past few decades. structural
steel decks have become an Increasingly
Important factor in the roof construction
Industry. Steel decks are unsuitable for
the direct application of BUR and,
therefore. require a surfacing substrate
which generally consists of rigid insulation board. However, steel roof deck
constructionsprovide a unique condition
wherein high temperature developed
within the structure.possiblyas a result of
isolatedlocal fire conditions, could cause
gasesto be liberatedfrom combustiblesIn
the roof construction components and
could contribute to the spread of fire on
the underside of the deck. In order to
qualify as Class I roof deck assemblies,
19
ROOF INSULATION~
the heat release rates of the roof
assemblymust be within acceptablelimits
developed by FM to insure that the
components within the assemblywill not
contribute directly to the initial spread of
fire under the steel deck. Specific
minimum thicknesses of perlite, fiberboard, glassfiberboard, and cellular glass
were initially found to provide the
thermal barrier qualities necessary to
provide this protectk>n. However, the
need for greater insulation efficiency
without the added cost of multila~r
construction and the design need for
lower deadweight load factors gave birth
to products known as composite.
The compositescombine the excellent
thermal efficiency of polyurethane foam
(Figure 1) and the thermal barrier
qualities of certain inorganic substrates.
Typically, the composite roof insulation
board consists of a specific bottom
substrate thickness of perlite, mineral
fiber, or glass fiberboard integrally
laminatedto a core of polyurethane foam
and a uniform top surface faced with an
asphalt saturated roofing felt or fibrous
glass mat for maximum strength and
adhesion to the roofing membrane.
Composite roof insulation is generally
produced in 3' x 4' or 4' x 4' panel sizes
manufactured
on a continuous
lamination boardstock facility. Product
thicknessrange from 1-1/4 to 5-9/16".
The published thermal conductance
values (C-value) and corresponding
thicknesses of several competitive
composite roof insulation products are
given in Table I. The product manufacturers' literature should be consult-
ed for more specific thermal data.
Composite roof Insulation is not
limited to steel-deck assembUes, but
rather enjoys widespread use over
noncombustiblestructural decks such as
concrete, gypsum, asbestos-cementand
other Class I struCtural decks such as
impregnated wood or cement fiber.
Structural component composite insulation panels are also available and at
least one manufacturer offers a composite of perUte-urethane-perlite.
The current manufaCturers'literature
should be consulted for definition of
specific construction assemblies, and
several approved construction design
assemblies are described by Factory
Mutual System and Underwriters laboratories, Inc., Guides and BuUetins.
...
TABLE
C-VALUECOMPARISONCHARTOF
COMPETITIVECOMPOSITE
ROOFINSULATIONPRODUCTS
(1)
Thermal
Conductance,
C-Factor
17
15
13
12
11
.109
.10
.093
09
08
.07
.069
.061
.06
.OS
Celotex
Tempchek
Plus.
Apache
Millox
Grefco
Permalite
PK ..
NAG
Composite
JM
Fesco Foam
Panel Era
Insul Roof I
FURl
1.25"
1.8"
1.5'
1.6'
1.4"
1.5"
1.6"
1.2"
1.50"
1-9/16'
1-5/8"
1-1/2"
1-5/8"
1.4"
1.6"
1.9"
1.75"
1.75
1-3/4"
1.75'
1-9/16'
2'
1.8'
2.5"
2.0"
2.0'
2"
2.00'
2-1/4"
2.5"
2.5'
2-1/2'
2.50"
2-1/2"
2.0"
1-11/16"
1-13/16"
.,.t
2.25'
2.5"
2.8"
3.2"
2.75"
3.0"
2.75"
3.0"
.049
.041
.04
.035
.031
. 02
(1) Values taken from published product literature
. Nominal thickness includes facers
..Facernot includedin nominal thickness
20
USM
Suprathane
Class I
2-3/4"
3"
2.75"
3.00"
2-1/4"
2-1/2"
2-3/4"
3-1/4"
3.0"
3.5"
4.0"
4.5"
2-7/8"
3-7/16'
5-9/16"