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Spread of fire in residential-type wood-frame construction
SPREAD OF FIRE I N RESIDENTIAL-TYPE WOOD-FRAME CONSTRUCTION by
W . T a y l o r
PREFACE
With t h e p r e s e n t e m p h a s i s on e n e r g y c o n s e r v a t i o n , r i g i d p l a s t i c - foam m a t e r i a l s a r e becoming w i d e l y used i n r e s i d e n t i a l c o n s t r u c t i o n .
I t i s r e c o g n i z e d , however, t h a t t h e s e c e l l u l a r m a t e r i a l s c a n , u n d e r some c i r c u m s t a n c e s , i n c r e a s e t h e h a z a r d s from a c c i d e n t a l f i r e s . A t e s t s e r i e s t o examine t h e f i r e p e r f o r m a n c e of foamed p l a s t i c s i n w a l l s t r u c t u r e s t y p i c a l of r e s i d e n t i a l c o n s t r u c t i o n was u n d e r t a k e n i n a n I n d u s t r i a l F e l l o w s h i p program s p o n s o r e d j o i n t l y by t h e S o c i e t y of t h e P l a s t i c s I n d u s t r y of Canada and t h e N a t i o n a l R e s e a r c h C o u n c i l of Canada. T h i s r e p o r t d e s c r i b e s t h e r e s u l t s of p a r t of t h i s i n v e s t i g a t i o n c o n c e r n i n g t h e f i r e b e h a v i o u r of " s u p e r - i n s u l a t e d ' ' wood-frame s t r u c t u r e s i n which t h e c o n v e n t i o n a l c e l l u l o s i c s h e a t h i n g i s r e p l a c e d by a r i g i d foamed- p l a s t i c b o a r d .
The i n v e s t i g a t i o n was p a r t of a program e x a m i n i n g t h e f i r e b e h a v i o u r of foamed p l a s t i c s u s e d a s b u i l d i n g i n s u l a t i o n . The a u t h o r , D r . W i l l i a m T a y l o r , h e l d t h e p o s i t i o n of DBR P l a s t i c s R e s e a r c h F e l l o w from 1979 t o 1981. O t h e r r e p o r t s p r e p a r e d by D r . T a y l o r d u r i n g h i s s t a y w i t h t h e D i v i s i o n a r e :
-
E v a l u a t i o n of t h e r m a l b a r r i e r s f o r foam p l a s t i c s i n s u l a t i o n ( I n t e r n a l R e p o r t No. 466) - S p r e a d of f i r e i n v e r t i c a l c o n c e a l e d s p a c e s c o n t a i n i n g foamed- p l a s t i c s i n s u l a t i o n : P a r t I . P o l y u r e t h a n e s and p o l y i s o c y a n u r a t e s ( I n t e r n a l R e p o r t No. 468) P a r t 11. Expanded P o l y s t y r e n e s ( I n t e r n a l R e p o r t No. 469) - E v a l u a t i o n of t h e e f f e c t i v e n e s s of f i r e b a r r i e r s i n p r e v e n t i n g f i r e s p r e a d i n c o n c e a l e d s p a c e s ( I n t e r n a l R e p o r t No. 470) The D i v i s i o n of B u i l d i n g R e s e a r c h g r e a t l y a p p r e c i a t e s t h e i n t e r e s t and s u p p o r t of t h e S o c i e t y of t h e P l a s t i c s I n d u s t r y i n t h i s program. Ottawa November 1 9 8 1 C . B.
Crawford D i r e c t o r DBR/NRCNATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEARCH
DBR INTERNAL REPORT NO. 4 7 1
SI'IIL21) OF F I R E IN RESIDENTIAL-TYPE WOOD-FRAME CONSTRIIC'IION
l)!. I$. 'I~:l>.lor
Checked by: '1'. 2 . I ] . Approved by: L .
W
.
G.
Date: Novem1,er- 198 1SPREAD OF FIRE IN RESIDENTIAL-TYPE WOOD-FRAME CONSTRUCTION
W . Taylor
The r e c e n t emphasis on energy c o n s e r v a t i o n has l e d t o a demand f o r i n c r e a s e d i n s u l a t i o n o f r e s i d e n t i a l housing. One method o f i n s u l a t i o n c o n s i s t s of wrapping a c o n v e n t i o n a l l y - i n s u l a t e d frame b u i l d i n g with an a d d i t i o n a l i n s u l a t i n g b l a n k e t o f foamed p l a s t i c , t h e r e b y r e p l a c i n g t h e s t a n d a r d s h e a t h i n g m a t e r i a l . The i n f l u e n c e o f t h i s foamed p l a s t i c on t h e f i r e s a f e t y o f t h e s t r u c t u r e a s compared t o a wood-frame b u i l d i n g without t h i s p l a s t i c h a s been b r i e f l y i n v e s t i g a t e d i n t e s t programs sponsored by t h e S o c i e t y o f t h e P l a s t i c s I n d u s t r y I n c . I n one c a s e 1
,
corner-room i n t e r i o r f i r e t e s t s were c a r r i e d o u t , u s i n g a 13.5 kg wood c r i b a s t h e f i r e s o u r c e , t o e v a l u a t e t h e f i r e s a f e t y o f both u n i n s u l a t e d and a s p h a l t / p a p e r - f a c e d , g l a s s - f i b r e i n s u l a t e d , wood- frame wall c o n s t r u c t i o n s o v e r which 38 mm expanded p o l y s t y r e n e e x t e r n a l s h e a t h i n g had been a p p l i e d . While t h e p o l y s t y r e n e n e a r t h e burning c r i b melted s u b s t a n t i a l l y , t h e f i r e d i d n o t p e n e t r a t e t h e gypsum-board i n t e r i o r w a l l of t h e s t r u c t u r e , and i t was concluded t h a t under t h e s e c o n d i t i o n s t h e expanded p o l y s t y r e n e d i d n o t c o n t r i b u t e t o t h e f i r e h a z a r d .Another t e s t 2 was designed t o determine if supplementary f i r e - blocking between t h e f i r s t and second f l o o r s o f s i n g l e - f a m i l y d w e l l i n g s was needed when u s i n g a polyurethane-based foam a s e x t e r i o r s h e a t i n g i n a g l a s s - f i b r e i n s u l a t e d , wood-frame c o n s t r u c t i o n . In t h i s t e s t t h e i n t e r i o r o f t h e s t r u c t u r e was s u b j e c t e d t o a s t a n d a r d ASTM El19 f i r e
3
exposure
.
The t e s t showed no evidence of v e r t i c a l spread o f f i r e t o t h e s e c o n d - s t o r e y wall above t h e f i r e compartment when e i t h e r c e l l u l o s i cf i b r e b o a r d o r urethane-foam s h e a t h i n g was used; it was t h e r e f o r e con- cluded t h a t u r e t h a n e foam d i d not r e q u i r e e x t r a f i r e - s t o p p i n g between f l o o r s .
The s e r i e s o f t e s t s d e s c r i b e d i n t h i s r e p o r t was undertaken t o f u r t h e r e v a l u a t e t h e f i r e performance of t r s u p e r - i n s u l a t e d " wood-frame c o n s t r u c t i o n s and t o determine if t h e u s e of foamed p l a s t i c e x t e r n a l s h e a t h i n g i n c r e a s e d t h e f i r e hazard by c o n t r i b u t i n g t o t h e s p r e a d o f flames i n t h e wall c a v i t i e s .
TEST FACILITY AND PROCUEDURE
An experimental r i g was used t o s i m u l a t e a t y p i c a l r e s i d e n t i a l wood-frame wall c o n s t r u c t i o n ( F i g . 1 ) . The wall framing c o n s i s t e d of 38 mrn x 89 mm s p r u c e s t u d s l o c a t e d on 600 mm c e n t r e s . The t o p and bottom p l a t e s , which a l s o comprised 38 mm x 89 mm s p r u c e , were a t t a c h e d t o t h e ends o f t h e s t u d s by e n d - n a i l i n g . Two modules, each o f them 1.25 m wide by 2.5 m h i g h , were i n s t a l l e d , one above t h e o t h e r , t o s i m u l a t e a two-storey assembly 5 m i n h e i g h t . The two s i d e s o f t h e assembly were l i n e d with 12.5 mm m a r i n i t e boards.
Each t e s t module was b u i l t up a s f o l l o w s ( F i g . 2 ) . The i n t e r i o r w a l l o f 1 2 . 5 mm r e g u l a r gypsum board was n a i l e d t o t h e wood f r a m i n g and a vapour b a r r i e r o f 0 . 1 mm p o l y e t h y l e n e f i l m was a t t a c h e d t o t h e gypsum. The w a l l c a v i t i e s between t h e s t u d s were i n s u l a t e d w i t h 85 mm t h i c k , u n f a c e d g l a s s - f i b r e b a t t s (R v a l u e 1 2 . 5 ) . The s h e a t h i n g was a t t a c h e d t o t h e o u t s i d e o f t h e s t u d framework and c o v e r e d by a l a y e r o f b u i l d i n g p a p e r . The e x t e r i o r c l a d d i n g was t h e n m e c h a n i c a l l y f a s t e n e d , t h r o u g h t h e s h e a t h i n g , d i r e c t l y t o t h e s t u d s o r , i n t h e c a s e o f PVC s i d i n g , t o n a i l e r s t r i p s which were n a i l e d t h r o u g h t h e s h e a t h i n g t o t h e s t u d s . Thermocouples were l o c a t e d v e r t i c a l l y a t i n t e r v a l s a l o n g t h e
i n t e r f a c e between t h e e x t e r i o r c l a d d i n g and s h e a t h i n g t o measure temper- a t u r e s d u r i n g t h e t e s t .
The f i r e s o u r c e f o r t h e t e s t s was a n a t u r a l g a s b u r n e r c o m p r i s i n g a p i p e 25 mm i n d i a m e t e r w i t h a s e r i e s o f 24 r a d i a l h o l e s 4.75 mm i n d i a m e t e r s e t a t 50 mm i n t e r v a l s a l o n g i t s l e n g t h . The n a t u r a l g a s f l o w t h r o u g h t h i s b u r n e r was m a i n t a i n e d c o n s t a n t d u r i n g t h e t e s t s a t a l e v e l t o p r o d u c e a h e a t o u t p u t o f 25 kW. T h i s same f i r e s o u r c e was used i n s i m i l a r t e s t s on a s s e m b l i e s o f n o n - c o m b u s t i b l e c o n s t r u c t i o n 4 .
T e s t program f o c u s e d on d e t e r m i n i n g t h e e x t e n t o f v e r t i c a l p r o - p a g a t i o n o f f i r e w i t h i n t h e w a l l , from t h e lower s t o r e y t o t h e second- s t o r e y w a l l above i t , v i a t h e r o u t e p r e s e n t e d by burned-out s h e a t h i n g . S i n c e t h e e f f e c t i v e n e s s o f t h e i n t e r i o r gypsum w a l l a s a f i r e b a r r i e r was n o t p a r t o f t h e s t u d y , it was assumed t h a t f i r e somehow p e n e t r a t e d i n t o t h e w a l l c a v i t y . The s o u r c e f l a m e s were t h e r e f o r e a p p l i e d , f o r a p e r i o d o f 10 m i n u t e s , t h r o u g h a 25 mm wide s l o t which was l e f t open a t t h e bottom o f t h e t e s t s t r u c t u r e . Two s e r i e s o f t e s t s were c a r r i e d o u t : i n one s e r i e s t h e f l a m e s were i n t r o d u c e d t h r o u g h t h e i n s i d e w a l l ; i n t h e o t h e r , flame e n t r y was t h r o u g h t h e e x t e r i o r w a l l . I n t h e l a t t e r s e r i e s , when t h e e x t e r i o r c l a d d i n g was a c o m b u s t i b l e m a t e r i a l , t h e lower 0 . 7 5 m
o f t h e assembly was c o v e r e d w i t h 1 2 . 5 mm gypsum board t o p r e v e n t t h e
s o u r c e b u r n e r from i m m e d i a t e l y i g n i t i n g t h e c l a d d i n g and t o a l l o w p r o g r e s s o f t h e f i r e i n s i d e t h e c a v i t y t o be o b s e r v e d . TEST MATERIALS The s h e a t h i n g and e x t e r i o r c l a d d i n g m a t e r i a l s e v a l u a t e d a r e l i s t e d i n T a b l e I . The r a n g e o f c o m b i n a t i o n s and c o n f i g u r a t i o n s t e s t e d i s shown i n T a b l e 11. TEST RESULTS a ) Flame e n t r y t h r o u g h t h e i n t e r i o r w a l l When t h e f l a m e s o u r c e was a p p l i e d t h r o u g h a n o r i f i c e a t t h e b a s e o f t h e gypsum b o a r d s forming t h e i n t e r i o r w a l l , t h e r e s u l t s were g e n e r a l l y s i m i l a r f o r a l l t h e c o m b i n a t i o n s o f s h e a t h i n g and e x t e r i o r c l a d d i n g t e s t e d ( T a b l e 1 1 ) . The f i r e p r o g r e s s e d v e r t i c a l l y f o r a l i m i t e d d i s t a n c e i n t o t h e c a v i t y and s l i g h t l y damaged t h e assembly. Both t h e vapour b a r r i e r and t h e g l a s s - f i b r e i n s u l a t i o n m e l t e d i n t h e a r e a d i r e c t l y a f f e c t e d by t h e f l a m e s . The p r o t e c t i o n o f t h e s h e a t h i n g by t h e g l a s s - f i b r e i n s u l a t i o n
r e s u l t e d i n o n l y l i m i t e d m e l t i n g o v e r t h e lower 0 . 5 m o f t h e p o l y - s t y r e r l c she:ithing and i n s u r f a c e c h a r r i n g o v e r a s i m i l a r a r e a when polyurethane o r c e l l u l o s i c f i b r e b o a r d s h e a t h i n g was u s e d . The wood s t u d s were a l s o c h a r r e d i n t h e immediate a r e a o f f l a m e impingement and t h e s u r f a c e c h a r r i n g e x t e n d e d v e r t i c a l l y a b o u t 0 . 3 5 m.
'(he flame d i d n o t p e n e t r a t e t h e e x t e r i o r c l a d d i n g o f t h e a s s e m b l y , even when t h e c l a d d i n g was a c o m b u s t i b l e m a t e r i a l (plywood, p o l y ( v i n y 1 c h l o r i d e ) ) . The maximum t e m p e r a t u r e r i s e r e c o r d e d by t h e t h e r m o c o u p l e s i n t h e s p a c e between s h e a t h i n g and c l a d d i n g was 50°C a t a p o i n t 1 m above t h e b a s e o f t h e a s s e m b l y . Above t h i s l e v e l t h e t e m p e r a t u r e i n c r e a s e d l e s s t h a n 5°C.
These r e s u l t s i n d i c a t e t h a t , w i t h f i r e s o r i g i n a t i n g i n s i d e a d w e l l i n g , v e r t i c a l s p r e a d t o a second s t o r e y v i a t h e w a l l c a v i t y o r by f l a m e t r a v e l up t h e o u t s i d e s u r f a c e o f t h e s t r u c t u r e i s u n l i k e l y t o o c c u r i n wood- frame c o n s t r u c t i o n s t h a t a r e i n s u l a t e d w i t h g l a s s f i b r e combined w i t h any commonly-available s h e a t h i n g m a t e r i a l , i n c l u d i n g foamed p l a s t i c s .
b) Flame e n t r y t h r o u g h e x t e r i o r w a l l
F i r e s p r e a d was more e x t e n s i v e i n t e s t s i n which t h e s o u r c e f l a m e s werc i n t r o d u c e d from t h e o u t s i d e o f t h e t e s t w a l l s i n c e t h i s made t h e c o m b u s t i b l e s h e a t h i n g m a t e r i a l s more d i r e c t l y a c c e s s i b l e t o t h e f l a m e s . 'The e x t e n t o f v e r t i c a l p r o p a g a t i o n was i n f l u e n c e d by t h e a v a i l a b l e a i r s p a c e between t h e s h e a t h i n g and t h e e x t e r i o r c l a d d i n g o f t h e a s s e m b l y . TEST WITH M I N I M U M A I R SPACE
When t h e a i r s p a c e i n t h e assembly was r e d u c e d t o a minimum, t h e f i r e s p r e a d o n l y s l i g h t l y i n t h e i n s u l a t e d c a v i t y w i t h e a c h o f t h e f o u r combinatiolls o f m a t e r i a l s t e s t e d i n t h i s c o n f i g u r a t i o n (Table 11). With t h e c e l l u l o s i c f i b r e b o a r d and t h e p o l y u r e t h a n e s h e a t h i n g , t h e s h e a t h i n g m a t e r i a l , b u i l d i n g p a p e r and wood s t u d s showed s m o u l d e r i n g and b u r n i n g from t h e p o i n t o f f l a m e impingement t o a d i s t a n c e o f 0 . 3 5 m v e r t i c a l l y i n t o t h e c a v i t y . A f t e r t h e s o u r c e f l a m e s were s h u t o f f , s m o u l d e r i n g c o n t i n u e d i n t h e c a v i t y f o r a b o u t 15 m i n u t e s b e f o r e p y r o l y s i s c e a s e d . The f i b r e b o a r d , however, r e t a i n e d s u f f i c i e n t h e a t s o t h a t t h e f l a m e s r c v i v c d when t h e e x t e r i o r c l a d d i n g o f t h e a s s e m b l y was removed one hour l a t e r . (Removing t h e c l a d d i n g i n c r e a s e d t h e a i r s u p p l y t o t h e
s m o u l d e r i n g a r e a s . ) Heat r e t e n t i o n d i d n o t o c c u r w i t h t h e p o l y u r e t h a n e s h e a t h i n g .
With t h e expanded p o l y s t y r e n e s h e a t h i n g , m e l t i n g and s h r i n k a g e o f t h e s h e a t h i n g opened up a n a i r s p a c e i n s i d e t h e c a v i t y , c a u s i n g t h e wood s t u d s t o b u r n more a c t i v e l y . The f i r e t h e n climbed a l o n g t h e s t u d s a d i s t a n c e o f 0 . 7 5 m b e f o r e i t p e t e r e d o u t 45 m i n u t e s l a t e r .
TESTS WITH A 15
MM AIR SPACE
(vhen an a i r s p a c e was a l l o w e d between t h e e x t e r i o r c l a d d i n g and t h e s h e a t h i n g , t h e f i r e burned more a c t i v e l y and e x t e n s i v e l y i n t h e c a v i t y i n a l l t h e t e s t s c a r r i e d o u t ( T a b l e 1 1 ) . The f i r e t e n d e d t o p r o g r e s s a l o n g
one o r more of t h e wood s t u d s i g n i t e d e a r l y i n t h e t e s t and continued t o burn s t e a d i l y even a f t e r t h e s o u r c e flames were removed.
When t h e e x t e r i o r c l a d d i n g comprised PVC s i d i n g , h e a t from t h e combustion i n s i d e t h e c a v i t y wall caused t h e lowest c o u r s e o f s i d i n g t o s o f t e n and d i s t o r t w i t h i n 8 minutes o f t h e s t a r t o f t h e t e s t . The s i d i n g p u l l e d away from t h e s i d e s of t h e assembly, exposing t h e
smouldering wood s t u d s behind t o a p l e n t i f u l s u p p l y of a i r . The s t u d s b u r s t i n t o flame and t h e f i r e s p r e a d up both s i d e s o f t h e s t r u c t u r e along t h e PVC s i d i n g and p o l y s t y r e n e s h e a t h i n g .
A s i m i l a r s i t u a t i o n developed with t h e plywood c l a d d i n g . The f i r e i n t h e c a v i t y p r o g r e s s e d up t h e wood s t u d s , c a u s i n g t h e plywood
immediately above t h e gypsum panel t o c h a r and t h e n b u r s t i n t o flame. T h i s occurred most r a p i d l y w i t h p o l y s t y r e n e s h e a t h i n g which caused t h e plywood c l a d d i n g t o burn a c t i v e l y o n l y 10 minutes i n t o t h e t e s t .
With p o l y u r e t h a n e o r c e l l u l o s i c f i b r e b o a r d s h e a t h i n g t h e v e r t i c a l p r o g r e s s o f t h e flames was s l o w e r , and t h e plywood began t o burn
a c t i v e l y about 25 minutes i n t o t h e t e s t . The d i f f e r e n c e i n t i m e s c a l e i s probably due t o t h e f a c t t h a t both p o l y u r e t h a n e and f i b r e b o a r d t e n d t o form a c h a r r e s i d u e which remains i n p l a c e i n t h e c a v i t y , l i m i t i n g a c c e s s o f a i r t o t h e wood s t u d s . I n c o n t r a s t , expanded p o l y s t y r e n e s h r i n k s and m e l t s , t h e r e b y i n c r e a s i n g t h e a i r s p a c e i n t h e c a v i t y and a l l o w i n g g r e a t e r v e n t i l a t i o n t o enhance t h e burning o f t h e wood s t u d s .
I n a l l t e s t s with a combustible c l a d d i n g m a t e r i a l , t h e f i r e i n t h e c a v i t y p e n e t r a t e d t h e e x t e r i o r c l a d d i n g and, i n e f f e c t , circumvented any f i r e s t o p between s t o r e y s by t r a v e l l i n g up t h e o u t s i d e s u r f a c e o f t h e s t r u c t u r e .
When t h e c l a d d i n g was gypsum, t h e f i r e which developed d i d n o t p e n e t r a t e t o t h e e x t e r i o r , b u t s p r e a d e x t e n s i v e l y i n s i d e t h e c a v i t y w i t h a l l t h r e e t y p e s o f s h e a t h i n g . I n i t i a l l y t h e s h e a t h i n g melted o r
smouldered and 5 minutes l a t e r t h e wood s t u d s a l s o i g n i t e d . Burning continued a f t e r t h e s o u r c e flames were s h u t o f f and t h e f i r e climbed t h e c a v i t y u n t i l , one hour l a t e r , i t reached t h e j u n c t i o n between t h e lower and upper modules o f t h e assembly. A t t h i s p o i n t t h e t e s t was t e r m i n a t e d . Cracks had developed i n t h e gypsum c l a d d i n g a f t e r about 40 minutes, t h e r e - by a l l o w i n g a c c e s s t o a d d i t i o n a l oxygen which helped m a i n t a i n combustion
i n t h e c a v i t y .
Examination of t h e c a v i t y a f t e r t h e t e s t r e v e a l e d t h a t t h e f i r e had e s s e n t i a l l y consumed most of t h e s h e a t h i n g and g l a s s - f i b r e i n s u l a t i o n i n t h e lower 1 . 2 m o f t h e assembly; above t h a t l e v e l , damage was confined t o a r e a s immediately a d j a c e n t t o t h e wood s t u d s . The s h e a t h i n g between t h e s t u d s was r e l a t i v e l y u n a f f e c t e d and t h e g l a s s - f i b r e i n s u l a t i o n beneath was a l s o undamaged ( F i g . 3 ) . The wood s t u d s were s e v e r l y burned o v e r most o f t h e 2.5 m h e i g h t o f t h e module and i t was a p p a r e n t t h a t , i n t h e l a t t e r s t a g e s of t h e t e s t , t h e f i r e had s p r e a d mainly v i a t h e wood s t u d s . The r e s u l t s were s i m i l a r f o r both c e l l u l o s i c f i b r e b o a r d and foamed-
The t e s t r e s u l t s i n d i c a t e t h a t i n g l a s s - f i b r e i n s u l a t e d , wood- frame c o n s t r u c t i o n s , r e p l a c i n g c o n v e n t i o n a l c e l l u l o s i c f i b r e b o a r d s h e a t h i n g by c e l l u l a r p l a s t i c s , such a s expanded p o l y s t y r e n e o r r i g i d p o l y u r e t h a n e foam, d o e s n o t add t o t h e f i r e h a z a r d of t h e s t r u c t u r e . They a l s o show t h a t a f i r e o r i g i n a t i n g i n t h e i n t e r i o r o f t h e b u i l d i n g i s u n l i k e l y t o s p r e a d t o an u p p e r s t o r e y v i a t h e i n s u l a t e d c a v i t y and t o t h u s c r e a t e f l a m e s p r e a d t h r o u g h t h e s h e a t h i n g . When t h e f i r e p e n e t r a t e s t h e w a l l c a v i t y from t h e o u t s i d e , v e r t i c a l p r o p a g a t i o n t h r o u g h t h e c a v i t y t o a n u p p e r s t o r e y i n t h e a b s e n c e of a f i r e s t o p i s p o s s i b l e when t h e r e i s an a i r s p a c e between t h e e x t e r i o r c l a d d i n g and t h e s h e a t h i n g . Minimizing t h e a i r s p a c e can e f f e c t i v e l y l i m i t t h e f i r e p r o p a g a t i o n . I t a p p e a r s t h a t t h e n a t u r e o f t h e s h e a t h i n g m a t e r i a l has l i t t l e i n f l u e n c e on t h e flame s p r e a d s i n c e t h e f i r e s p r e a d s p r i m a r i l y v i a t h e wood s t u d s .
References
1. Anderson, E.L. Full-scale fire tests on EPS exterior sheathing
-
interior fire source. SWRI report No. 03-4907-00, San Antonio, Texas, December 1977.
2. Degenkolb, J.G. Evaluation of the performance in a fire test
situation of isocyanate-based foam used as sheathing in
residential construction. Society of the Plastics Industry Inc., Urethane Division, New York, 1979.
3. Fire tests of building construction and materials. ASTM designation
E119-79, 1979 Annual Book of ASTM Standards, Part 18,
p.
808Philadelphia.
4. Taylor, W. Spread of fire in vertical concealed spaces containing
foamed plastics insulation. Parts
I
and 11. National ResearchCouncil of Canada, Division of Building Research, DBR Internal Report Nos. 468, 469, Ottawa.
TABLE I MATERIALS EVALUA'I'ED Sheathing --- - 1:xtcri o r cladding . - - - -. - - 12.5 mrn Cellulosic fihreboard
25 m m Extruded expanded polystyrene, density 3 2 kg/m3
25 m m Aluminum-foil-faced rigid polyurethane, density 32 kg/m 3
9 m m Exterior grade plywood 12.5 m m Regular gypsum board
1.1 mm Poly (vinyl chloride) ( P V C ) (conforming to CGSB 41-GP-24M)
TABLE I I
SHEATHING CONFIGURATIONS TESTED
S h e a t h i n g P o l y s t y r e n e P o l y u r e t h a n e F i b r e b o a r d i r S p a c e E x t e r i o 0 15 - C l a d d i n g
\
P 1 ywood E*
I * " , E 1, E I . E E E C,>.j>surn Board Ilol}, (V i l l y 1 c h l o r i d e )A+
i n d i c a t e s t e s t c o n d u c t e d w i t h f i r e ~ ~ c n c t r a t i o n thr.oug!ll t l l c i r l t c r i o r wa 11 '1: i r l d i c n t e s t c s t c o n d u c t e d w i t h f i r e p e n e t r a t i o n t h r o u g h t h e o s t c r - i o r w a l l,.-38 mm x 89 mm TOP PLATE ,/ /' r 3 8 mm x 89 rnrn WOOD STUDS EXTERIOR
,
12.5 mm G Y P S U M BOARD 85 mm UNFACED G L A S S 12.5 rnrn M A R l N l T E BOARD SHEATH IIVG 38 mrn x 89 rnm BOTTOM PLATE'"
38 rnrn x 89 mrn TOP PLATE C L A D D I N G SHEATH I N G 12.5 rnrn G Y P S U M BOARD F I G U R E 1 V I E W O F T Y P I C A L A S S E M B L Y O F C O M B U S T I B L E C O N S T R U C T I O Nr 38 rnm x 89 mrn STUD
F I G U R E 2
C R O S S - S E C T I O N O F T Y P I C A L W A L L C O N S T R U C T I O N
WOOD STUDS CHARRED F I G U R E 3 T E S T S W I T H F L A M E E N T R Y T H R O U G H E X T E R I O R W A L L : 15 m m A I R G A P . D I A G R A M O F T Y P I C A L A P P E A R A N C E O F I N S U L A T E D C A V I T Y A F T E R T E S T ( E X T E R I O R C L A D D I N G R E M O V E D )
