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Construction Technology Update, 1997-12-01
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Fire protection of windows using sprinklers
Kim, A. K.; Lougheed, G. D.
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NRC Publications Record / Notice d'Archives des publications de CNRC:
https://nrc-publications.canada.ca/eng/view/object/?id=ee364f9d-e252-4a4d-9d42-8381b9deb026 https://publications-cnrc.canada.ca/fra/voir/objet/?id=ee364f9d-e252-4a4d-9d42-8381b9deb026b y A .K. Kim a nd G.D. Loughe e d
Building ow ners and designers have been limited in the extent to w hich they
can use glazing in fire-rated separations. This Update presents the results of
IRC research on the use of dedicated sprinkler systems to protect glazing
in fires and provides guidelines that w ill ensure effective protection in
different situations.
C o n s t r u c t i o n T e c h n o l o g y U p d a t e N o . 1 2
Th ere is an in creasin g d em an d for th e u se of glazin g assem blies in fire sep aration s an d in th e bu ild in g en velop e for aesth etic, secu rity an d econ om ic reason s. Ord in ary glass can n ot be u sed becau se th erm al stresses w ill cau se it to sh atter after on ly a few m in u tes of exp osu re to fire. Th erefore, for fire-rated assem blies, North Am erican m od el bu ild in g cod es lim it vertical glazin g to w ired glass in steel fram es w ith a m axim u m glazin g d im en sion of 1400 m m . Th is rep resen ts a severe restriction for d esign ers.
To overcom e th ese lim itation s w ith ou t com p rom isin g fire safety, fire research ers at
NRC’s In stitu te for Research in Con stru ction (IRC) d evelop ed a p rotection m eth od in volvin g th e u se of a d ed icated au tom atic sp rin kler system th at ap p lies a film of w ater to th e glazin g assem bly.[1] Th e IRC in vesti-gation s d em on strated th at tem p ered or h eat-stren gth en ed glass (w h ich , by itself, p rovid es on ly m in im al p assive fire p rotection ), p ro-tected by su ch a sp rin kler system , w ill rem ain in tact for m ore th an 1 h ou r. Based on th ese stu d ies, th e sp rin kler-p rotection system h as been accep ted by som e cod e au th orities for u se in fire sep aration s in bu ild in gs for sp ecific ap p lication s.
T he rm a l Shoc k
Tests w ith a sm all-scale rad ian t p an el d em on strated th at cold w ater ap p lied to h ot glazin g can cau se p rem atu re failu re of th e glass.[2] With ou t w ater p rotection , tem p ered an d h eat-stren gth en ed glazin g can su stain a glazin g tem p eratu re on th e exp osed sid e of m ore th an 350°C. How ever, w h en w ater w as sp rayed on to th e h ot glazin g, th e glazin g failed at m u ch low er tem p eratu res. Th e critical tem p eratu res establish ed for h eat-stren gth en ed an d tem p ered glazin g are 150–165°C an d 200°C, resp ectively.[2] Th e critical tem p eratu re for p lain glass (80–90°C) is too low to allow for effective p rotection u sin g a sp rin kler system . Th ese in vestigation s establish ed th at in ord er for a sp rin kler to p rovid e effective p rotection , it m u st be activated before th e glazin g tem p eratu re exceed s its critical level.
Fire Protection of Window s
Using Sprinklers
Figure 1.Section through test room
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Baffle Gravel Exposure fire Glazing Exhaust stack inlet Gas Air
West Linear propane burner East Control
thermocouples
2
De sign Conside ra t ions
Specific design considerations for a d ed icated sp rin kler-p rotection system for a fu ll-h eigh t (floor to ceilin g) w in d ow assem bly are ad d ressed below. Th ese in clu d e: • w in d ow w id th ,
• m u llion d ep th , an d • m u lti-sp rin kler system s.
For all tests, a fast-resp on se sp rin kler w as u sed .[1,2,4] In th e tests, a sp rin kler w as in stalled in a h orizon tal orien tation an d p osition ed at th e top cen tre of a w in d ow assem bly. Th e cen trelin e of th e sp rin kler’s d eflector w as located 50 m m below th e top w in d ow fram e, an d th e d eflector p osition ed
13 m m from th e glass (see Figu re 2). Th e sp rin kler w as activated by th e fire, an d th e w ater p ressu re at th e sp rin kler w as m ain -tain ed at 145 kPa.
Window Width
Tests w ere con d u cted to d eterm in e th e m axim u m w id th of glazin g th at can be p ro-tected u sin g a sin gle sp rin kler. For glazin g 3000 m m w id e, w ith n o sep aratin g m u llion , th e w ater sp ray from a sin gle sp rin kler p ro-vid ed good coverage for all su rfaces of th e w in d ow an d fram e, w ith ad equ ate w ater film flow on th e glazin g su rface (see Figu re 3). Glazin g tem p eratu res reach ed stead y con d i-tion s in less th an 10 m in u tes an d th e w in d ow system m ain tain ed its in tegrity for th e 2-h ou r test d u ration .
Mullion Depth
Tests were conducted with 10-mm and 25-mm d eep m u llion s. Th e resu lts in d icated th at m u llion s w ith d ep th s of 25 m m or m ore in terfered w ith th e w ater sp ray to th e glazin g on both sid es of th e m u llion . Th e con clu sion is th at a sin gle sp rin kler w ill n ot p rovid e ad equ ate p rotection for su ch a glazin g assem bly. For w in d ow s w ith m u llion s m ore th an 25 m m d eep , th erefore, m u lti-sp rin kler p rotection system s sh ou ld be con sid ered .[4]
Multi-Sprinkler Systems
Wh en a m u lti-sp rin kler system is u sed to p rotect a w id e w in d ow or a w in d ow w ith a d eep m u llion , th e w ater sp ray from th e first
N RC Te st Fa c ilit y
Th e fu llscale fire tests on sp rin klerp rotected w in d ow assem -blies w ere con d u cted in a room w ith a floor area of 3600 m m by 3300 m m an d a ceilin g h eigh t of 3300 m m .[2] A sketch of th e test facility is sh ow n in Figu re 1.
Fire exp osu re w as p rovid ed by a lin ear p rop an e bu rn er in stalled n ear th e floor ad jacen t to th e w est w all of th e test room . Com bu stion air w as su p p lied th rou gh a p erforated steel d u ct located ben eath th e bu rn er. Com bu stion p rod u cts an d steam w ere w ith d raw n from th e room u sin g n atu ral ven tilation th rou gh tw o exh au st stacks w ith a 600-m m by 450-m m cross-section .
Fire Ex posure
Th e fire exp osu re w as establish ed by con d u ctin g a p relim in ary test w ith ou t sp rin kler op eration to d eterm in e th e p rop an e flow rate requ ired to m ain tain th e average tem p eratu re in th e en closed com p artm en t as close as p ossible to th e stan d ard tim e-tem p eratu re cu rve, u sed for d eterm in in g th e fire resistan ce of bu ild in g assem blies.[3]
Th e p rop an e flow rate d eterm in ed in th e calibration test w as th en u sed for th e tests w ith sp rin kler p rotection . Th e on ly sp rin klers op eratin g d u rin g th e tests w ere th ose u sed to p rotect th e w in d ow assem bly. Alth ou gh su ch a system w ou ld , in m ost cases, be u sed in a bu ild in g w ith overall sp rin kler p rotection , it is assu m ed th at th e w in d ow -p rotection system w ou ld be a d ed icated on e, sep arate from th e m ain sp rin kler system .
Figure 3.Location of single sprinkler for protection for full-height window assembly (elevation)
max 3000 1500 3300 Single sprinkler 50
Figure 2.Sprinkler location relative to full-height window assembly (section)
13 mm
50 mm
To p rovid e ad equ ate p rotection , th e fast-resp on se sp rin kler m u st h ave a tem p era-tu re ratin g of 74°C an d a Resp on se Tim e In d ex (RTI) of 22.7 m1/ 2s1/ 2 or low er.
in terest to bu ild in g d esign ers for aesth etic reason s. A stu d y to d eterm in e th e effectiven ess of su ch a system revealed tw o con -cern s: sp rin kler activation tim e an d w ater sp ray p attern on to th e glazin g su rface.
Sprinkler activation time. Ceilin g-m ou n ted
sp rin klers, both stan d ard an d fast-resp on se, d id n ot activate in tim e to p rotect fu ll-h eigh t tem p ered glazin g from a sm all fire located on th e floor ad jacen t to th e glass.[4] Th is lim its th e u se of ceilin g-m ou n ted sp rin klers in p rotectin g glazin g assem blies. Th ey can , h ow ever, be u sed in th ose cases w h ere th e base of th e glazin g is at least 1000 m m above th e floor. In su ch in stan ces, th e ch an ces of h avin g a localized fire im p in gin g d irectly on th e glazin g are sm all an d , th u s, th e system would not likely be faced with this challenge.
Spray pattern. A series of sp ray-p attern
tests in d icated th at th e p robability of glass breakage from fire exp osu re in creases gen -erally w ith an in crease in sill d ep th , an in crease in sp rin kler h eigh t above th e top of th e glazin g an d an in crease in sp rin kler d istan ce from th e w in d ow.[2] Th is is based on th e size of th e d ry area on th e glazin g observed for each con figu ration . As th e d ry area in creases, th ere is an in creased p roba-bility of glass breakage from th erm al stress. Based on th ese stu d ies, m axim u m s for each p aram eter w ere establish ed as follow s (see Figu re 5):
• a sill d ep th of 150 m m ,
• a sp rin kler h eigh t above th e w in d ow of 450 m m , an d
• a sp rin kler d istan ce of 600 m m from th e w in d ow.[4]
For d esign p u rp oses, th e th ree p aram eters are in terrelated . Th e d esign er sh ou ld select d istan ces th at w ill m axim ize w ater sp ray to all areas of th e glazin g.
Fire tests u sin g a ceilin gm ou n ted sp rin -kler w ith a 1800-m m -w id e tem p ered glazin g system at th ese m axim u m d istan ces
sh ow ed th at th e w ater sp ray w as su fficien t to p rovid e 1-h ou r fire p rotection .
If a ceiling-mounted fast-response sprinkler is located at an id eal p osition — 300 m m aw ay from th e glazin g su rface, an d 300 m m above th e top of a w in d ow w ith a w in d ow -sill d ep th of 50 m m or less — th e w ater sp ray p rovid es su fficien t p rotection for a w in d ow assem bly w ith tem p ered glazin g an d a m axim u m w id th of 2600 m m (see Figu re 6) for at least on e h ou r.[2] For a w id er w in d ow, a m u lti-sp rin kler system sh ou ld be u sed . Th e d elay in sp rin kler sp rin kler activated cou ld d elay th e activation
of an ad jacen t sp rin kler. Tests w ere con -d u cte-d to stu -d y th e p roblem .
For very wide windows without a mullion, th e activation tim es of sp rin klers, located 2000 m m from a sp rin kler op eratin g at a p ressu re of 145 kPa, w ere in th e ran ge of 5 to 7 m in u tes. How ever, th e critical tem p eratu re for th e glazin g w as n ot reach ed u n til 10 to 11 m in u tes. As su ch , th e secon d sp rin kler w ou ld activate before critical con d ition s are reach ed . Th erefore, a w id e w in d ow or a w in d ow w ith ou t m u llion s can be p rotected by a m u lti-sp rin kler system , w ith ou t th e con cern of d elayed sp rin kler
activation , w h en sp rin klers are located at least 2000 m m ap art (see Figu re 4).[4]
When there is a centre mullion (of at least 50-m m d ep th ) betw een th e sp rin klers, th e in flu en ce of w ater sp ray from th e ad jacen t sp rin kler is n ot sign ifican t; in th is case, th e secon d sp rin kler activated in less th an 40 secon d s.[2]
Th e activation tim e of th e secon d sp rin kler is d ep en d en t on sp rin kler orien tation an d location . If th e geom etry is ch an ged , th e overall p rotection system sh ou ld be evalu ated to d eterm in e th e effectiven ess of th e d ed icated sp rin kler system .
Ce iling-M ount e d Sprink le rs
Th e u se of ceilin g-m ou n ted p en d en t sp rin klers to p rotect glazing assemblies is of particular
3
Figure 4.Location of sprinklers in multi-sprinkler system for protection of wide windows (elevation)
greater than 3000
at least 2000 max 1500
Sprinklers
Figure 5.Limiting distances for ceiling-mounted pendent sprinklers (section)
max 450
1000
max 600
activation d u e to ad jacen t sp rin kler op era-tion is n ot a p roblem if th e sp rin klers are sp aced at least 1800 m m ap art.
Sum m a ry
Th e IRC stu d ies in d icated th at tem p ered or h eat-stren gth en ed glazin g cou ld be p rotected for m ore th an on e h ou r u sin g a d ed icated sp rin kler system . How ever, th ere are certain lim itation s on glazin g w id th , m u llion d ep th , th e u se of sin gle vs. m u lti-sp rin klers, an d th e u se of ceilin g sp rin klers. For th e sp rin kler system to p erform effectively in p rotectin g w in d ow assem blies, th ese lim i-tation s m u st be taken in to accou n t. Th ey are su m m arized as follow s:
• A d ed icated fast-resp on se sp rin kler can be u sed to p rotect a fu ll-h eigh t w in d ow assem bly from both a large com p artm en t fire an d a sm all fire located on th e floor im m ed iately ad jacen t to th e glazin g. Th e sp rin kler sh ou ld be m ou n ted ad jacen t to the glazing at the top centre of the window assem bly.
• A sin gle sp rin kler sh ou ld n ot be u sed to p rotect glazin g w id er th an 3000 m m . • A sin gle sp rin kler sh ou ld n ot be u sed to
p rotect a w in d ow assem bly w ith a m u l-lion h avin g a d ep th of 25 m m or m ore. • A m u lti-sp rin kler system can be u sed
to p rotect glazin g w id er th an 3000 m m if th e sp rin klers are sp aced at least 2000 m m ap art.
• If th ere is a cen tre m u llion w ith a d ep th of at least 50 m m located betw een th e
sp rin klers, th e sp acin g betw een th e sp rin klers n eed n ot be lim ited .
• A ceilin g-m ou n ted p en d en t sp rin kler can be used to protect a window assembly whose base is at least 1000 m m above th e floor. • For a ceilin g-m ou n ted p en d en t sp rin kler,
th e m axim u m s for certain p aram eters w ere establish ed as follow s: a sill d ep th of 150 m m , a sp rin kler h eigh t above th e w in d ow of 450 m m , an d a sp rin kler d istan ce from th e w in d ow assem bly of 600 m m . Becau se th ese th ree p aram eters are in terrelated , th e d esign er sh ou ld select d istan ces th at m axim ize w ater sp ray to all areas of th e glazin g.
• For a ceilin gm ou n ted fastresp on se sp rin -kler at th e id eal location (300 m m above th e w in d ow an d 300 m m from a window with a sill depth of 50 mm or less), glazin g w ith a m axim u m w id th of 2600 m m can be p rotected for u p to 1 h ou r.
• For multi-sprinkler arrangements mounted on th e ceilin g, th e sp rin klers sh ou ld be sp aced at least 1800 m m ap art.
Re fe re nc e s
1. Rich ard son , J.K. an d Oleszkiew icz, I. Fire Tests on Win d ow Assem blies Protected by Au tom atic Sp rin klers, Fire Tech n ology, Vol. 23, No. 2, May 1987, p p . 115-132.
2. Kim , A.K. an d Lou gh eed , G.D. Th e Protection of Glazin g System s w ith Ded icated Sp rin klers, Jou rn al of Fire Protection En gin eerin g, Vol. 2, 1990, p p . 49-59.
3. CAN4-S101-M82, Stan d ard Meth od s of Fire En d u ran ce Tests for Bu ild in g Con stru ction an d Materials, Un d erw riters’ Laboratories of Can ad a, Scarborou gh , ON, 1982.
4. Kim , A.K. Protection of Glazin g in Fire Sep aration s by Sp rin klers, Proceed in gs of th e Sixth In tern ation al In terflam Con feren ce, Oxford , UK, 1993, p p . 83-93.
Dr. A .K. Kiman d Dr. G.D. Loughe e d are sen ior research officers in th e Fire Risk Man agem en t Program of th e N ation al Research Cou n cil’s In stitu te for Research in Con stru ction .
“Construction Te chnology Up d a te s” is a se rie s of te chnica l a rticle s conta ining p ra ctica l inform a tion d istille d from re ce nt construction re se a rch.
For more information, contact Institute for Research in Construction, National Research Council of Canada, Ottaw a K1A 0R6
Telephone: (613) 993-2607; Facsimile: (613) 952-7673; Internet: http://irc.nrc-cnrc.gc.ca
© 1997
Nation al Research Cou n cil of Can ad a Decem ber 1997
ISSN 1206-1220
Figure 6.Location (ideal) of ceiling-mounted pendent sprinkler relative to window assembly (elevation)
2600
1000
