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Polyurethane insulation and its effects on the intensity of fire
Mehaffey, J. R.
Sex
THI.
N21d National Research Conseil national
no.
1365
I
+
Council Canada de recherches Canadac e 2
B U Z Institute for lnstitut de Research in recherche en
- - - -. Construction construction
Polyurethane Insulation and Its Effects on
the Intensity of Fire
by
J.R.
MehaffeyAMALYZED
Appeared in
Proceedings of The Society of the Plastics Industry of Canada
Sixth Annual Rigid Polyurethane Foam Committee Fall General Meetin and Conference
September 11 - 13 1 85, Hull, Quebec Paper No. 9, 14p.
8,
(IRC Paper No. 1365)
Reprinted with permission
Price $2.00 NRCC 25849 N R C
-
C l 8 f i BLDG. RES.t l B R A R Y
I C N H C-
fClST1
Ce document ddcrit quelques-uns des risques d'incendie dscoulant de l'emploi d'isolant en mousse dans les batiments. La littdrature portant sur le sujet indique que les risques sont rgduits lorsque la mousse est protegee du cats intdrieur du batiment, car elle ne contribue pas directement au dtiveloppement de l'incendie en propageant les flames. Lorsque l'isolant est protggd par une barrisre thermique, on observe qu'il n'influe pas de manisre sensible sur le dsveloppement de l'incendie, pas plus avant qu1apr2s l'embrasement gsdral.
POLYURETHANE INSULATION AND ITS EFFECTS ON THE INTENSITY OF FIRE
J. R. Mehaf f ey
Division of Building Research National Research Council of Canada
ABSTRACT
Some of the potential fire hazards resulting from the use of
' foamed-plastic insulation in buildings are considered. Published literature
indicates that if foamed plastic is protected on the room side, the hazards are diminished since the foam does not contribute directly to fire growth by spreading flames. When insulation is protected by a thermal barrier, it is found that both preflashover fire growth and post-flashover fire severity are not greatly affected by the insulation.
INTRODUCTION
The increased use of foamed-plastic insulation in buildings has led to concern over fire safety. References to potential fire hazards resulting from the increased use of such insulation have frequently appeared in technical literature, in discussions at scientific gatherings, and in the popular press. That the concern is topical is reflected by the fact that in October of last year a two-day conference entitled "Fire and Cellular
Plastics" (1) was convened, at which 19 papers were presented. Many of those papers addressed issues related to the use of cellular plastics as thermal insulation.
The concern centres around four perceived problems:
1) foamed-plastic insulation is combustible and, consequently, will add to
the fire load in a building,
2)
if exposed as a wall or ceiling lining in a room, foamed-plasticinsulation will spread flames quickly when ignited,
3 ) the products of combustion of foamed-plastic insulation are toxic
(polyurethane has occasionally been singled out in this regard), and
4 ) by its nature, insulation traps heat near a fire (or a potential ignition
source such as an electrical fixture) which may lead to a faster fire growth and a more intense fire.
A few general statements about each of these concerns is in order to put into perspective this presentation on polyurethane foam insulation and its effect on the intensity of fire.
CONTRIBUTION TO THE FIRE LOAD
Consider first the contribution of foamed-plastic insulation to the fire load in a building. The fire load of a single room is simply the quantity of heat that would be released should the combustible contents of the room be burned.
In large buildings, most rooms will have at most one wall that needs to be insulated, as that wall alone forms the outside of the building. For rooms with a high fire load, such as those found in residences and offices ( 2 ) , it can be demonstrated that polyurethane insulation in one wall yields an incremental increase in the fire load of less than 5%. For rooms with a low fire load, such as those found in hotels, the incremental increase could be higher than 5% but less than 10%.
Consequently, introducing polyurethane foam insulation in one wall of a room yields a perceptible increase in the fire load; but it is not a large increase.
SPREAD OF FLAME BY EXPOSED INSULATION
It has been known for some time
(3)
that many foamed-plasticinsulations exposed as a wall or ceiling lining in a room spread flames quickly when ignited, giving rise to high temperatures and what is often described as an excessive amount of smoke. In response to this potential hazard, the National Building Code of Canada
(4)
requires thatfoamed-plastic insulation in buildings be protected on the room side.
In combustible construction, this protection may take the form of one of several permitted finishes. In fact, some of the permitted protections are themselves combustible; for example, plywood.
In noncombustible construction, this protection must take the form of a thermal barrier. If the insulation has a flame-spread rating of 25 or less, a lo-minute thermal barrier is required.
A
lo-minute thermal barrier is one which, when tested to CAN4-S101 (5) (or UCL-S124 ( 6 ) ) , will not exceed an average temperature rise of 13g°C on the unexposed face of the barrier after a period of 10 minutes.A
12.7 mm thick gypsum board mechanically fastened to the supporting assembly independent of the insulation is one example of alolninute thermal barrier. If the insulation has a flame-spread rating between 25 and 500 (whether it is foamed-plastic or not) it must again be protected with a lo-minute thermal barrier, except in unsprinklered high buildings (usually defined as buildings exceeding 18 m in height), in which case a 45-minute thermal barrier is required. Two layers of 15.9 mn Type X gypsum board give this protection, provided the first layer is mechanically fastened to the supporting assembly independent of the insulation.
Finally, in the 1985 National Building Code, the use of polyurethaqe insulation encased by sheet steel in factory-assembled exterior wall panels is permitted in specified applications for the first time.
Although foamed-plastic insulation was now prevented from contributing directly to early fire growth by regulations for covering it, the question then arose: "If fire ever gets into that cavity space undetected, by
whatever means, with all that combustible insulation in there, isn't it likely to spread quickly?".
A
test program, jointly sponsored by the Society of the Plastics Industry of Canada and the National Research Council of Canada (NRCC), and conducted by W. Taylor and K. Choi (7), examined the contribution ofwere i n t r o d u c e d i n t o a s i m u l a t e d w a l l c a v i t y c o n t a i n i n g i n s u l a t i o n . It was found i n t h e s e s t u d i e s and i n a n i n d e p e n d e n t B r i t i s h s t u d y (8) t h a t f i r e s p r e a d w i t h i n t h e c a v i t y depends l i t t l e on t h e i n s u l a t i o n employed b u t
c r u c i a l l y on t h e s u p p l y of a i r i n t h e c a v i t y . The s u p p l y of a i r depends, i n t u r n , on how wide t h e a i r s p a c e i n t h e c a v i t y i s , and on w h e t h e r o r n o t t h e c a v i t y i s s e a l e d .
It was concluded from t h e s e e x p e r i m e n t s t h a t e x c e s s i v e f i r e s p r e a d i n a c a v i t y i s u n l i k e l y , p r o v i d e d t h e a i r s p a c e i s k e p t a t a w i d t h less t h a n
25 mm. I n a d d i t i o n , i t h a s been found t h a t f i r e s t o p s a l s o p r o v i d e a good p r o t e c t i o n measure a g a i n s t f i r e s p r e a d i n c a v i t i e s . With p r o p e r d e s i g n , one need n o t f e a r e x t e n s i v e f i r e s p r e a d t h r o u g h w a l l c a v i t i e s f i l l e d w i t h
c o m b u s t i b l e i n s u l a t i o n .
TOXICITY OF THE PRODUCTS OF COMBUSTION
It i s n o t uncommon t h e s e d a y s t o h e a r comments s u c h a s : "The smoke produced i n b u i l d i n g f i r e s i s g e t t i n g more and more t o x i c as more and more p l a s t i c m a t e r i a l s a r e used". C e r t a i n l y many f i r e f i g h t e r s a p p e a r t o be convinced t h a t t h i s i s so.
The t o x i c h a z a r d s a s s o c i a t e d w i t h t h e b u r n i n g of b u i l d i n g m a t e r i a l s and f u r n i s h i n g s a r e p r e s e n t l y t h e s u b j e c t of much r e s e a r c h . Although e x c e p t i o n s have been documented, i t i s u s u a l l y c a r b o n monoxide t h a t i s t h e p r i n c i p a l
t o x i c t h r e a t t o l i f e (9). Although p o l y u r e t h a n e i n s u l a t i o n i s known t o produce HCN when i t b u r n s ( l o ) , t h e r e seems t o b e no d e f i n i t e proof t h a t under f i r e c o n d i t i o n s p o l y u r e t h a n e foam i n s u l a t i o n augments t o x i c h a z a r d s beyond t h e l e v e l s t h a t a l r e a d y e x i s t i n b u i l d i n g f i r e s ( 1 1 ) .
I n c i d e n t a l l y , s e v e r a l t e s t methods a r e b e i n g developed u n d e r t h e
a u s p i c e s of concensus groups l i k e ASTM f o r s c r e e n i n g m a t e r i a l s on t h e b a s i s of f i r e g a s t o x i c i t y . P r o g r e s s i s hampered by t h e f a c t t h a t t h e t o x i c h a z a r d depends n o t o n l y on t h e chemical n a t u r e of t h e m a t e r i a l t e s t e d , b u t a l s o on t h e f i r e e x p o s u r e i n t h e t e s t . A s i t i s p r e s e n t l y n o t p o s s i b l e t o p r e d i c t p r o d u c t performance i n b u i l d i n g f i r e s based on p r o d u c t performance i n f i r e t o x i c i t y t e s t s , i t may be some t i m e b e f o r e s u c h t e s t methods f i n d a p p l i c a t i o n i n Canada. I n t h e i n t e r i m , i t i s assumed t h a t smoke-control measures a d o p t e d i n compliance w i t h b u i l d i n g code r e q u i r e m e n t s w i l l p r o t e c t o c c u p a n t s from b o t h smoke and t o x i c g a s e s .
TRAPPING OF HEAT BY INSULATION
Of c o u r s e , t h e p u r p o s e of a d d i n g i n s u l a t i o n t o b u i l d i n g s i s t o k e e p t h e h e a t i n d u r i n g t h e w i n t e r . However, w h e t h e r c o m b u s t i b l e o r n o t , i n s u l a t i o n
w i l l a l s o p r e v e n t h e a t from e s c a p i n g from a b u i l d i n g s h o u l d a f i r e s t a r t w i t h i n it. By t r a p p i n g h e a t n e a r a f i r e , i n s u l a t i o n may l e a d t o a f a s t e r f i r e growth and a more i n t e n s e f i r e e v e n i f t h e i n s u l a t i o n i t s e l f d o e s n o t burn. T h i s f a c t h a s l e d some t o q u e s t i o n whether e n e r g y c o n s e r v a t i o n and f i r e s a f e t y o b j e c t i v e s are m u t u a l l y e x c l u s i v e .
To show t h a t t h i s i s a s u b j e c t worthy of c o n s i d e r a t i o n , a b r i e f comment i s needed on t h e dynamics of compartment o r room f i r e s .
DYNAMICS OF ROOM FIRES
When an o b j e c t b e g i n s t o burn i n a room, i t produces a g r e a t d e a l of smoke and h o t combustion gas which, due t o buoyant f o r c e s , r i s e t o form a h o t smoky l a y e r i n t h e upper p a r t of t h e room.
This h o t l a y e r l o s e s h e a t t o t h e w a l l s and c e i l i n g a t a r a t e t h a t depends on t h e i r thermal i n s u l a t i n g p r o p e r t i e s . The b e t t e r t h e i n s u l a t i n g v a l u e of t h e w a l l s and c e i l i n g , t h e l e s s h e a t l o s t t o them. ( I n c i d e n t a l l y , i f t h e w a l l s and c e i l i n g a r e good i n s u l a t o r s , t h e i r exposed s u r f a c e
temperature rises q u i c k l y b u t l i t t l e h e a t i s t r a n s f e r r e d i n t o them. It i s t h i s quick r i s e i n t h e s u r f a c e t e m p e r a t u r e of good i n s u l a t o r s t h a t i s
b e l i e v e d t o c a u s e t h e h i g h f l a m m a b i l i t y of some foamed p l a s t i c s . ) So a s i t u a t i o n r e s u l t s i n which t h e b e t t e r t h e thermal i n s u l a t i n g v a l u e of t h e w a l l s and c e i l i n g , t h e h o t t e r t h e smoky l a y e r and t h e s u r f a c e t e m p e r a t u r e of
t h e w a l l s and c e i l i n g .
Now, thermal r a d i a t i o n from t h e h o t l a y e r and from t h e w a l l s and
c e i l i n g f a l l s on t h e burning o b j e c t , l i k e l y i n c r e a s i n g i t s r a t e of burning, and a l s o f a l l s on a l l o t h e r o b j e c t s i n t h e room. The f i r e could go o u t i f , f o r example, t h e f i r s t o b j e c t burns completely b e f o r e o t h e r s s t a r t , o r i f s u f f i c i e n t oxygen cannot g e t i n t o t h e room t o keep t h e o b j e c t burning. Sometimes, however, t h e h e a t i n g of t h e o t h e r combustibles i n t h e room
c o n t i n u e s t o t h e p o i n t where t h e y r e a c h t h e i r i g n i t i o n t e m p e r a t u r e s more o r l e s s simultaneously. Flames t h e n suddenly sweep a c r o s s t h e room i n v o l v i n g most combustibles i n t h e f i r e . This r a p i d t r a n s i t i o n from t h e burning of one o r two o b j e c t s t o full-room involvement i s r e f e r r e d t o as f l a s h o v e r .
It can be expected t h a t t h e b e t t e r t h e i n s u l a t i n g v a l u e of t h e room-lining m a t e r i a l s , t h e sooner and more l i k e l y f l a s h o v e r w i l l occur.
Even a f t e r f l a s h o v e r , h e a t cannot be d i s s i p a t e d e a s i l y i n a room l i n e d w i t h good i n s u l a t o r s , s o t h e f i r e i s l i k e l y t o burn a t a h i g h temperature.
EXPERIMENTS CONDUCTED AT THE FIRE RESEARCH FIELD STATION
That t h i s can be q u i t e a s i g n i f i c a n t e f f e c t i s shown by t h e r e s u l t s of two room-burn experiments conducted r e c e n t l y a t t h e F i r e Research F i e l d S t a t i o n of NRCC. The two experiments were conducted i n a room about t h e s i z e of an o r d i n a r y bedroom. The f l o o r was 2.4 m by 3.6 m, and t h e c e i l i n g was a t a h e i g h t of 2.4 m. The f i r e l o a d , c o n s i s t i n g of wooden c r i b s , was
chosen t o s i m u l a t e t h a t of a h o t e l room. The window, which was l e f t open, had a n a r e a about 9% t h a t of t h e f l o o r .
The rooms were i d e n t i c a l i n e v e r y way, e x c e p t t h a t i n room 1 t h e w a l l s were l i n e d w i t h b r i c k , and i n room 2 w i t h i n s u l a t i n g f i r e b r i c k . I n both rooms t h e c e i l i n g and f l o o r were covered w i t h f i b e r f r a x board. The t h e r m a l p r o p e r t i e s of t h e room-lining m a t e r i a l s employed i n t h e two t e s t s a r e
Table 1
Thermal P r o p e r t i e s of I n t e r i o r F i n i s h M a t e r i a l s
Thermal Thermal Thermal
Density S p e c i f i c Heat C o n d u c t i v i t y I n e r t i a R e s i s t a n c e
M a t e r i a l p (kg m-3) c (J kg'l~'l) k (W/m K)
fi
S I I m p e r i a lBrick 1935 1025 0.80 1260 0.07 0.4
F i r e b r i c k 722 1000 0.25 425 0.25 1.4
F i b r e f r a x 3 18 7 50 0.072 131 0.53 3.0
The c r i b s i n t h e room were i g n i t e d and t h e subsequent f i r e behaviour
monitored. I n F i g u r e 1 t h e t e m p e r a t u r e of t h e f i r e i s p l o t t e d a s a f u n c t i o n of t i m e f o r b o t h rooms. Because t h e w a l l s of room 2 were much b e t t e r
i n s u l a t o r s than t h o s e of room 1, t h e f i r e temperature i n room 2 was h i g h e r throughout t h e d u r a t i o n of t h e f i r e . (Note t h a t t h e d u r a t i o n of t h e f i r e i s u n a f f e c t e d by t h e thermal p r o p e r t i e s of t h e w a l l s . )
"
0 5 1 0 15 2 0 2 5 3 0
TIME, m i n
F i g u r e 1. Temperatures of f i r e g a s e s i n two rooms l i n e d w i t h d i f f e r e n t m a t e r i a l s
A s f a r a s l i f e s a f e t y i s concerned, t h e t i m e t o f l a s h o v e r ; t h a t i s , f u l l room involvement, must be c o n s i d e r e d a key parameter. C e r t a i n l y , a f t e r f l a s h o v e r t h e r e i s no chance of s u r v i v a l w i t h i n t h e room. T y p i c a l l y
the room approaches 600°C. In room
1
it took about 73 minutes for flashover to occur. In room 2, in which the walls were better insulators, it took only 23 minutes or so for flashover to occur.Following flashover there is close to a 200 C degree difference between the fire temperature of the room lined with brick and that of the room lined with insulating firebrick. If a concrete column supporting the floor above happened to pass through this room, it would experience a very different fire depending on the lining of the walls.
One way of visualizing the difference in severity of these two room fires is to compare them with the severity of the Standard Fire Resistance Test CAN4-S101. It can be shown that the fire in room
1
was equivalent in severity to a Fire Resistance Test of 25 minutes duration while room 2 was equivalent to such a test of 40 minutes duration.These two experiments demonstrate what other experimental (12) and theoretical (13) investigations have uncovered: As the insulating value of the interior linings of a room is increased:
1) the time to flashover decreases,
2) the post-flashover severity increases, and
3) the duration of the flaming stage of the fire is largely unaffected.
It is because of these well-documented findings that concern has often been expressed about a negative relationship between energy conservation
(increased insulation) and fire safety (14).
PROTECTED INSULATION
The findings cited previously relate to the effects of the thermal properties of room linings on fire behaviour. These findings are not
directly applicable to foamed-plastic thermal insulation, which is required by the NBCC to be installed behind the lining because of its combustible behaviour. The question then arises, "If foamed-plastic insulation is covered, do its thermal properties increase the risk of fire?".
HEAT CONDUCTION
To answer this question, we must appreciate that the nature of heat conduction through walls is different for normal heating processes and for fires.
For normal (non-fire) heating processes the time scale of heating (or cooling) is usually long enough that a steady-state condition is reached. The heat loss across a wall component depends only on the thermal
conductivity of the component material and its thickness. In fact, the thermal resistance or R-value obtained by dividing the thickness by the thermal conductivity is used under normal heating conditions for comparing products.
In a fire the time scales are fairly short. Typically, the duration of a preflashover fire is 5 to 20 minutes and that of the fully-developed
(post-flashover) stage is less than 30 minutes. In the early stages of fire, heat begins penetrating into the lining materials of the room. Since heat conduction does not proceed particularly quickly through most building materials, it takes some time before insulation behind the lining materials begins to heat up and slow down the rate of heat transfer through the
walls.
The depth to which heat penetrates the lining materials before flashover depends upon:
1)
the thermal diffusivity of the materials, K, and2 ) the duration of the preflashover stage, T.
For thicknesses of the lining material, a, such that
it can be shown that heat does not penetrate through the material during the preflashover fire.
In such cases, then, the initial growth of the fire will depend on the thermal properties of the linings, and not at all on the thermal properties of insulation behind the linings.
If, on the other hand,
which may occur, for example, if:
1) the lining material is a good conductor, 2) the lining material is thin, or
3)
the preflashover stage is of long duration (perhaps due to limited ventilation),heat conduction away from the fire through the walls can be strongly
influenced by materials behind the linings. The time to flashover becomes dependent on the thermal properties of the insulation: the better the insulation, the sooner flashover occurs.
As already mentioned, foamed-plastic insulation in noncombustible construction must be covered by either a lo-minute or a 45lninute thermal barrier. This means that if the barrier plus insulation were to be
subjected to a standard fire resistance test which simulates the severe exposure conditions of a post-flashover fire, the surface of the insulation would not heat up more than 139
C
degrees for 10 or 45 minutes,respectively. If the barrier plus insulation were to be exposed to the less severe exposure conditions of a preflashover fire, the insulation would have little influence on room-fire development.
In other words, if foamed-plastic insulation is protected by a
t h e time t o f l a s h o v e r u n l e s s t h a t time i s g r e a t e r t h a n 10 o r 4 5 - m i n u t e s , r e s p e c t i v e l y . Such a p e r i o d of t i m e should allow t h e occupants of t h e room t o e s c a p e from t h e f i r e .
What about t h e p o s t - f l a s h o v e r f i r e ? Does i n s u l a t i o n p r o t e c t e d by a thermal b a r r i e r cause h e a t t o be r e t a i n e d w i t h i n t h e f i r e room, r e s u l t i n g i n a h o t t e r and hence more s e v e r e f i r e ?
C e r t a i n l y , when a 45-minute t h e r m a l b a r r i e r i s employed, i t i s u n l i k e l y t h a t t h e thermal i n s u l a t i o n would i n any way e f f e c t t h e s e v e r i t y of t h e p o s t - f l a s h o v e r f i r e . The l e n g t h of t i m e i t t a k e s h e a t t o p e n e t r a t e t h e thermal b a r r i e r i s l o n g e r t h a n t h e d u r a t i o n of most f i r e s .
It i s n o t s o c l e a r what happens when a lo-minute t h e r m a l b a r r i e r i s employed. C e r t a i n l y t h e t e m p e r a t u r e up t o f l a s h o v e r and j u s t a f t e r f l a s h o v e r i s n o t a f f e c t e d by t h e i n s u l a t i o n . A s t h e f i r e burns l o n g e r ,
however, e f f e c t s may become apparent. But i s t h e hazard t o l i f e augmented
beyond t h a t a l r e a d y p r e s e n t e d by t h e f u l l y - d e v e l o p e d f i r e ? S e v e r a l f u l l - s c a l e experiments shed l i g h t on t h i s q u e s t i o n .
FULL-SCALE FIRE EXPERIMENTS
It i s , of c o u r s e , cheaper t o s t u d y t h e f i r e performance of b u i l d i n g m a t e r i a l s i n s m a l l - s c a l e experiments. U n f o r t u n a t e l y , t h e behaviour of t e s t samples i n such s m a l l s c a l e t e s t s o f t e n r e l a t e s only t o t h e p a r t i c u l a r c o n d i t i o n s of t h e t e s t . Attempts t o a s s e s s t h e p o t e n t i a l f i r e hazard of i n s u l a t i o n i n u s e i n v a r i a b l y r e q u i r e l a r g e - s c a l e t e s t i n g f a c i l i t i e s .
Although s e v e r a l d i f f e r e n t f u l l s c a l e t e s t p r o c e d u r e s have been used t o s t u d y t h e e f f e c t s of p r o t e c t e d i n s u l a t i o n , perhaps t h e e a s i e s t t o i n t e r p r e t a r e t h o s e t h a t a t t e m p t t o s i m u l a t e room f i r e s . The r e s u l t s of t h r e e s e r i e s of room-fire e x p e r i m e n t s , designed t o a s s e s s t h e e f f e c t on f i r e growth and i n t e n s i t y of employing p r o t e c t e d i n s u l a t i o n , g i v e a n a p p r e c i a t i o n of t h e
hazard involved. These experiments were conducted by:
1) The O l i n C o r p o r a t i o n Research C e n t e r , 1977 (151, 2) Owens-Corning F i b e r g l a s C o r p o r a t i o n , 1978 ( 1 6 ) , and
3 ) Ken Choi, NRC/SPI Fellow, 1984 (17).
These s e r i e s were a l l conducted i n rooms t h e s i z e of bedrooms,
2.4 m x 3.6 m i n a r e a and 2.4 m high.
OLIN CORPORATION, 1977
Eleven room-fire experiments were conducted i n t h e O l i n F i r e T e s t Laboratory (15) t o e v a l u a t e t h e u s e of p o l y u r e t h a n e s p r a y foam i n
r e s i d e n t i a l a p p l i c a t i o n s . The c o n s t r u c t i o n used was a w a l l w i t h s t a n d a r d
two-by-four s t u d s , backed w i t h 19 mm plywood. The i n s u l a t i o n s t e s t e d were:
( 1 ) none, ( 2 ) p o l y u r e t h a n e s p r a y foam, and ( 3 ) g l a s s - f i b r e b a t t i n g . Three d i f f e r e n t i n t e r i o r f a c i n g s were included: ( 1 ) f i n i s h e d plywood p a n e l l i n g ,
( 2 ) 12.7 mm gypsum w a l l b o a r d , and ( 3 ) f i n i s h e d plywood p a n e l l i n g o v e r gypsum wallboard.
V e n t i l a t i o n of t h e room was p r o v i d e d by a n open door. The i g n i t i o n s o u r c e was a 14 kg wooden c r i b p l a c e d i n a c o r n e r of t h e room.
The d a t a s u g g e s t t h a t p o l y u r e t h a n e s p r a y foam a p p l i e d behind a n
a d e q u a t e t h e r m a l b a r r i e r s u c h a s 12.7 mm gypsum w a l l b o a r d p r e s e n t s a h a z a r d no g r e a t e r t h a n when g l a s s - f i b r e i n s u l a t i o n o r no i n s u l a t i o n i s used. It
s h o u l d be n o t e d , however, t h a t t h e f i r e e x p o s u r e p r o v i d e d by a 14 kg wooden c r i b i n a room l i n e d w i t h gypsum w a l l b o a r d c a n h a r d l y b e c o n s i d e r e d s e v e r e . These c o n c l u s i o n s are o n l y a p p r o p r i a t e f o r p r e f l a s h o v e r f i r e growth.
OWENS-CORNING FIBERGLAS, 1978
Twenty-nine room-fire e x p e r i m e n t s were conducted by Owens-Corning
F i b e r g l a s C o r p o r a t i o n (16) t o e v a l u a t e t h e e f f e c t of i n c r e a s e d i n s u l a t i o n on f i r e b e h a v i o u r i n houses. Single-room s t r u c t u r e s were c o n s t r u c t e d of wooden s t u d s , f i n i s h e d w i t h 12.7 mm gypsum w a l l b o a r d , and backed w i t h 12.7 mm
plywood. These s t r u c t u r e s were e i t h e r : ( 1 ) u n i n s u l a t e d ; ( 2 ) i n s u l a t e d t o American F e d e r a l Housing A d m i n i s t r a t i o n recommendations (R-19 c e i l i n g ; R-11 w a l l s and f l o o r ) ; o r ( 3 ) i n s u l a t e d t o American e n e r g y - e f f i c i e n t home
recommendations (R-38 c e i l i n g ; R-19 w a l l s and f l o o r ) . I n a d d i t i o n , rooms were c o n s t r u c t e d from s h e e t m e t a l ( u n i n s u l a t e d ) and c o n c r e t e b l o c k
( u n i n s u l a t e d ) .
V e n t i l a t i o n was a g a i n p r o v i d e d by a n open door. The i g n i t i o n s o u r c e
was a 14 kg wooden c r i b p l a c e d i n a c o r n e r of t h e room.
The d a t a s u g g e s t e d t h a t t h e r e was no s i g n i f i c a n t impact o n f i r e
performance as a r e s u l t of i n c r e a s e d i n s u l a t i o n . I n a d d i t i o n , i t w a s found t h a t t h e i n t e r i o r s u r f a c e f i n i s h of t h e room had a g r e a t e r e f f e c t on t h e e a r l y s t a g e s of a f i r e t h a n d i d t h e l e v e l of i n s u l a t i o n .
Again, t h e f i r e e x p o s u r e p r o v i d e d by a 14 kg wooden c r i b i n a room l i n e d w i t h gypsum w a l l b o a r d c a n h a r d l y be c o n s i d e r e d s e v e r e . These c o n c l u s i o n s a r e o n l y a p p r o p r i a t e f o r p r e f l a s h o v e r f i r e growth.
KEN C H O I , NRCCISPI, 1984
R e c e n t l y , Ken Choi, a NKCC/SPI r e s e a r c h f e l l o w , conducted two s e r i e s of f u l l - s c a l e room-burn e x p e r i m e n t s a t t h e F i r e Research F i e l d S t a t i o n of NRCC.
I n f o r m a t i o n from o t h e r e x p e r i m e n t a l programs, s u c h a s t h e two j u s t o u t l i n e d , had a l r e a d y d e t e r m i n e d t h a t i n s u l a t i o n p r o t e c t e d by a t h e r m a l b a r r i e r d i d n o t a f f e c t e a r l y f i r e behaviour. Consequently, i n h i s e x p e r i m e n t s Choi c o n c e n t r a t e d on t h e e f f e c t s of i n s u l a t i o n p r o t e c t e d by a t h e r m a l b a r r i e r on p o s t - f l a s h o v e r f i r e s e v e r i t y . I n h i s f i r s t s e r i e s of e x p e r i m e n t s ( 1 7 ) , two w a l l s of t h e t e s t room were e i t h e r u n i n s u l a t e d o r i n s u l a t e d w i t h molded p o l y s t y r e n e , f o i l - f a c e d p o l y u r e t h a n e , o r e x t r u d e d p o l y s t y r e n e . It was d e c i d e d t h a t two w a l l s s h o u l d b e i n s u l a t e d t o s i m u l a t e t h e most a d v e r s e s c e n a r i o p o s s i b l e , t h a t of a room i n t h e c o r n e r of a b u i l d i n g . The f o u r w a l l s of t h e room were c o v e r e d by
16 mm Type X gypsum w a l l b o a r d e x c e p t f o r 0.3 m wide v e r t i c a l s t r i p s i n t h e two u n i n s u l a t e d w a l l s . Here t h e f i r e b r i c k of t h e o u t e r s t r u c t u r e w i t h i n which t h e room was c o n s t r u c t e d was l e f t bare.
10
V e n t i l a t i o n was provided by a window i n a r e a 9.3% t h a t of t h e f l o o r . The window was l e f t open d u r i n g t h e experiment.
I
The f i r e l o a d was provided by 240 kg of wood d i v i d e d among e i g h t wooden I
I
c r i b s . T h i s would be t y p i c a l of t h e f i r e load found i n o f f i c e s o r
dwellings. To r e a c h f l a s h o v e r a s q u i c k l y a s p o s s i b l e , a l l e i g h t c r i b s were i g n i t e d s i m u l t a n e o u s l y by small methanol pool f i r e s .
It should be p o i n t e d o u t t h a t , u n l i k e i n t h e s t u d i e s mentioned
p r e v i o u s l y , t h e g o a l i n t h i s program was t o s t u d y t h e p o s t - f l a s h o v e r f i r e . Great c a r e was t a k e n i n d e s i g n i n g t h e s e experiments t o e n s u r e a p r o p e r s i m u l a t i o n of t h e fully-developed s t a g e of t h e f i r e . Less e f f o r t was p u t i n t o s i m u l a t i n g t h e e a r l y s t a g e s of f i r e ( a l l e i g h t c r i b s were i g n i t e d s i m u l t a n e o u s l y ) , s o t h a t phase w i l l n o t be d i s c u s s e d .
The t e m p e r a t u r e i n t h e room i s shown i n F i g u r e 2. The f i r s t peaks of t h e c u r v e s r e p r e s e n t r a p i d burning of t h e methanol used t o i g n i t e t h e wooden
c r i b s . The sudden rises i n temperature t o over 600°C denote f l a s h o v e r .
I I 1
-
-
800 U 0 700 W E-
-
3 600-
:I
:1-
E W a-
-
-... . .. ... .
M O L D E D P S 200 100 0 I.-.-.
-t
P O L Y U R E T H A N E f---
i E X T R U D E D P S.-
C O N T R O L - II
I
I
0 10 20 3 0 40 50 6 0 T I M E , m i nF i g u r e 2. Temperatures of f i r e g a s e s i n rooms i n experiments conducted by
Note t h e n e g l i g i b l e d i f f e r e n c e s i n room t e m p e r a t u r e s a f t e r f l a s h o v e r between t h e u n i n s u l a t e d ( c o n t r o l ) and t h e i n s u l a t e d rooms. I n a d d i t i o n , t h e d u r a t i o n of t h e f i r e a p p e a r s n o t t o be s i g n i f i c a n t l y i n f l u e n c e d by t h e
p r e s e n c e of i n s u l a t i o n .
Thermocouples l o c a t e d a t t h e i n t e r f a c e of t h e i n s u l a t i o n and t h e gypsum w a l l b o a r d i n d i c a t e d t h e t e m p e r a t u r e r i s e c r i t e r i o n of 139 C d e g r e e s was exceeded a f t e r a b o u t 25 m i n u t e s i n t h e s e t e s t s .
The w a l l b o a r d c o n t i n u e d t o p r o t e c t t h e f o a m e d - p l a s t i c i n s u l a t i o n from b e i n g i g n t t e d a f t e r t h e 139 C d e g r e e t e m p e r a t u r e r i s e was exceeded.
Somewhere around t h e 4 0 - m i n u t e mark, t h e gypsum w a l l b o a r d c o l l a p s e d and t h e i n s u l a t i o n became i n v o l v e d i n t h e f i r e . T h i s d i d n o t a p p e a r t o
i n f l u e n c e t h e f i r e s e v e r i t y .
The t e m p e r a t u r e s measured a t a d e p t h of 2.2 cm i n t h e f i r e b r i c k of t h e w a l l s o p p o s i t e t h e two w a l l s c o n t a i n i n g t h e i n s u l a t i o n a r e shown i n
F i g u r e 3. The f i r e b r i c k w a l l s , which presumably are i n t e n d e d t o p r e v e n t f i r e from s p r e a d i n g t o o t h e r compartments, c a n be s e e n t o have e x p e r i e n c e d a f i r e no more s e v e r e when i n s u l a t i o n was i n s t a l l e d t h a n i n t h e p r i m a r y f i r e
( t h a t i s , when t h e r e was no i n s u l a t i o n ) .
-
.
. .
.
.
. . .
.
M O L D E D P S-
.-.-. P O L Y U R E T H A N E---
E X T R U D E D P S-
C O N T R O L 0 1 0 2 0 30 4 0 5 0 6 0 T I M E , m i n F i g u r e 3. Thermal r e s p o n s e of f i r e b r i c k i n e x p e r i m e n t s conducted by K.K. Choi ( 1 7 )The t e m p e r a t u r e r e s p o n s e of t h e s e w a l l s c a n b e u s e d t o show t h a t t h e s e f i r e s were e q u i v a l e n t i n s e v e r i t y t o a s t a n d a r d f i r e - r e s i s t a n c e test of
I
a p p r o x i m a t e l y 57 minutes.I n t h e second s e r i e s of e x p e r i m e n t s conducted by K. Choi, two w a l l s of t h e t e s t room were e i t h e r u n i n s u l a t e d o r i n s u l a t e d w i t h g l a s s f i b r e , s p r a y e d p o l y u r e t h a n e , o r e x t r u d e d p o l y s t y r e n e . The w a l l s of t h e room were a g a i n covered w i t h 16 mm Type X gypsum board which was a t t a c h e d t h i s time t o s t e e l s t u d s .
V e n t i l a t i o n was p r o v i d e d by a window i n a r e a 8.5% t h a t of t h e f l o o r . F i n a l l y , t h e f i r e l o a d was p r o v i d e d by 190 kg of wood d i v i d e d among e i g h t wooden c r i b s .
The r e s u l t s of t h e second s e r i e s have n o t y e t been p u b l i s h e d . They d i d , however, c o r r o b o r a t e t h e f i n d i n g s of t h e f i r s t s e r i e s ; namely, t h e u s e of f o a m e d - p l a s t i c i n s u l a t i o n p r o t e c t e d by 16 mm Type X gypsum i n two w a l l s of a room does n o t y i e l d a f i r e more s e v e r e t h a n i n a n u n i n s u l a t e d room o r one i n s u l a t e d w i t h g l a s s - f i b r e i n s u l a t i o n .
FOAMED-PLASTIC INSULATION I N EXTERIOR WALLS OF BUILDINGS
Today f o a m e d - p l a s t i c i n s u l a t i o n i s b e i n g u s e d i n o r on t h e e x t e r i o r w a l l s of b u i l d i n g s , a s w e l l a s w i t h i n c a v i t y w a l l s i n b u i l d i n g i n t e r i o r s . The p o t e n t i a l f i r e e x p o s u r e s and f i r e h a z a r d s a s s o c i a t e d w i t h s u c h e x t e r i o r i n s u l a t i o n a r e d i f f e r e n t from t h o s e o u t l i n e d i n t h i s p r e s e n t a t i o n .
The American S o c i e t y f o r T e s t i n g and M a t e r i a l s (ASTM) Committee E-5 on f i r e s t a n d a r d s h a s s e t up a t a s k group t o s t u d y t h e s u b j e c t . The Task Group
i s p r e s e n t l y p r e p a r i n g a White Paper e n t i t l e d " F i r e Risk Assessment f o r Foam P l a s t i c I n s u l a t i o n i n o r on E x t e r i o r Walls of Buildings". E v e n t u a l l y t h e Task Group may t a k e s t e p s t o d e v e l o p a f i r e t e s t method. It may b e u s e f u l f o r t h e R i g i d P o l y u r e t h a n e Foam Committee t o keep a b r e a s t of t h e Task Group d e l i b e r a t i o n s .
SUMMARY
The i n c r e a s e d u s e of f o a m e d - p l a s t i c i n s u l a t i o n i n b u i l d i n g s h a s l e d t o c o n c e r n o v e r f i r e s a f e t y . The r e q u i r e m e n t i n t h e N a t i o n a l B u i l d i n g Code of Canada t h a t foamed p l a s t i c b e p r o t e c t e d on t h e room s i d e d i m i n i s h e s t h e h a z a r d s by p r e v e n t i n g t h e foam from c o n t r i b u t i n g d i r e c t l y t o f i r e growth.
I n noncombustible b u i l d i n g s t h i s p r o t e c t i o n must t a k e t h e form of a t h e r m l b a r r i e r . It h a s been d e m o n s t r a t e d t h a t under such c o n d i t i o n s , b o t h p r e f l a s h o v e r f i r e growth and p o s t - f l a s h o v e r f i r e s e v e r i t y i n t h e f i r e room a r e n o t g r e a t l y a f f e c t e d by t h e i n s u l a t i o n . W i t h i n t h e c a v i t y w a l l ,
e x c e s s i v e E i r e s p r e a d c a n b e p r e v e n t e d by r e s t r i c t i n g t h e a i r s p a c e t o less
ACKNOWLEDGEMENT
T h i s p a p e r i s a c o n t r i b u t i o n from t h e D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research C o u n c i l of Canada.
REFEKENCES
1. P r o c e e d i n g s of t h e c o n f e r e n c e " F i r e and C e l l u l a r Polymers", Oct. 11 and 12, 1984, London, England, Queen Mary C o l l e g e , Wolfson F i r e and
Materials Centre.
2. 0. P e t t e r s s o n , S.-E. Magnusson, and J. Thor, " F i r e E n g i n e e r i n g Design of S t e e l S t r u c t u r e s " , Swedish I n s t i t u t e of S t e e l C o n s t r u c t i o n ,
Stockholm, B u l l e t i n 50 (1976).
3. R.B. Williamson and F.M. Baron, "A Corner F i r e T e s t t o S i m u l a t e R e s i d e n t i a l F i r e s " , J o u r n a l of F f r e and F l a m m a b i l i t y
k,
99 (1973)-4. N a t i o n a l B u i l d i n g Code of Canada 1985, N a t i o n a l Research Council of
Canada, A s s o c i a t e Committee on t h e N a t i o n a l B u i l d i n g Code, NRCC 23174 (1985).
5. CAN4-SlO1, "Standard Methods of F i r e Endurance T e s t s of B u i l d i n g
C o n s t r u c t i o n and M a t e r i a l s " , U n d e r w r i t e r s ' L a b o r a t o r i e s of Canada (1982).
6 . ULC S124, "Standard Method of T e s t f o r t h e E v a l u a t i o n o f ' ~ r o t e c t i v e
Coverings f o r Foamed P l a s t i c " , U n d e r w r i t e r s ' L a b o r a t o r i e s of Canada (1981).
7. K.K. Choi a n d W. T a y l o r , " C o m b u s t i b i l i t y of I n s u l a t i o n i n C a v i t y Walls", J o u r n a l of F i r e S c i e n c e s
2,
179 (1984).8. B. Rogowski, " F i r e Performance of Combustible I n s u l a t i o n i n Masonry
C a v i t y Walls", F i r e S a f e t y J o u r n a l
-
8, 119 (1984/85).9. B.C. Levin, " F i r e Deaths and Toxic Gases", Nature -9 300 18 (November 4, 1982).
10. D.A. P u r s e r and W.D. Woolley, " B i o l o g i c a l S t u d i e s of Combustion Atmospheres", J. of F i r e S c i e n c e s
-
1, 119 (1983).11. C. J. H i l a d o and P.A. H u t t l i n g e r , " T o x i c i t y of Off-Gases from Thermal I n s u l a t i o n " , J. of Thermal I n s u l a t i o n 4, 276 (1981).
-
12. D.G. Gluck, J.R. Hagan, and D.E. Hipchen, " F i r e Performance of C e l l u l a r P l a s t i c I n s u l a t i o n s i n C o n s t r u c t i o n " , F i r e J o u r n a l ,
74,
67 (November 1980).13. R.D. Peacock and J.N. B r e e s e , "Computer F i r e Modeling f o r t h e P r e d i c t i o n of F l a s h o v e r " , NBSIR 82-2516.
14. J.G. Degenkolb, "Will Energy Conservation have an Effect on the Fire
Protection of Buildings?
",
Building Standards, 142-147(September-October 1972).
15. D.A. Condit and A.D. Cianciolo, "Evaluation of Rigid Urethane Insulation for Residential Application by Compartment Corner Fire
Test", Fire Journal, 71 32 (May 1977). -9
16.
J.E. Prusaczyk,R.H.
Bell, B.W. Oberg, and P.C. Wilson, "FirePerformance Characteristics in Rooms as the Result of Increased Insulation", Society of Fire Protection Engineers, Technology Report 78-2 (1978).
17.
K.K.
Choi, "Effects of Foamed Plastic Insulation on Severity of RoomT h i s p a p e r i s being d i s t r i b u t e d i n r e p r i n t form by t h e I n s t i t u t e f o r R e s e a r c h i n C o n s t r u c t i o n . A l i s t of b u i l d i n g p r a c t i c e and r e s e a r c h p u b l i c a t i o n s a v a i l a b l e from t h e I n s t i t u t e may be o b t a i n e d by w r i t i n g t o t h e P u b l i c a t i o n s S e c t i o n , I n s t i t u t e f o r R e s e a r c h i n C o n s t r u c t i o n , N a t i o n a l Research C o u n c i l of C a n a d a , O t t a w a , O n t a r i o , K1A 0R6. C e document e s t d i s t r i b u g s o u s forme de t i r g - 3 - p a r t p a r 1 ' I n s t i t u t de r e c h e r c h e e n c o n s t r u c t i o n . On peut o b t e n i r une l i s t e d e s p u b l i c a t i o n s de 1 ' I n s t i t u t p o r t a n t s u r l e s t e c h n i q u e s ou l e s r e c h e r c h e s e n matisre d e bdtiment e n Q c r i v a n t ?i l a S e c t i o n d e s p u b l i c a t i o n s , I n s t i t u t de r e c h e r c h e en c o n s t r u c t i o n , C o n s e i l n a t i o n a l d e r e c h e r c h e s du Canada, Ottawa ( O n t a r i o ) , KIA OR6.
