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8/18/2019 07 ESL-HH-84-08-05
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AIJX J1,IARY COOLING LOADS IN PASSIVELY
AN EXPERIMENTAL RESEARCH
P. FAIREY
Pr inc ipa l Resea rc h Sc i e n t i s t
R
VIEIRA
A ss i s t a n t E ng ine e r
S. KALAGHCHY
COOLEI) BUILDINGS
STUDY
S. CH NDR
A c t ing D i r e c to r ,
RL
A KERESTECIOGLU
G r aduat e S tude n t A ss i s t a n t
Gradua te S tudent Ass is tant
Flor ida Sola r Energy Cente r
300 St a t e Road 401
Cape Can av era l, FL 32920
ABSTRACT
Current ly accepted methods of pass ive cool ing
of f s e t only sens ibl e bui ldin g loads . In th e warm, humid
s o u t h ea s t er n g u l f c o a s t c l i m a t e s t h e l a t e n t b u i l d i n g
load can comprise
35
of t h e bu i l d ing l oad i n t he
typi ca l r es idence . As the sen s ib le load on res idences
in t he se c l ima te s i s r educ ed o r o f f se t by pa s s ive
c oo l ing t e c hn ique s , t h i s l a t e n t c oo l i ng loa d pe r c e n t a ge
inc r e a se s r a p id ly . I n such r e s ide nc e s t he a ux i l i a r y
cool ing load cannot be e f fe c t iv e l y met by conven t iona l
cooling equipment .
The Florida Solar Energy Center (FSEC)
i s
examining
the a ux i l i a r y c oo l i ng r e qu ir e men t s o f r e s ide nc e s i n
warm, humid cl i mat es. The stud y addr esse e both th e
ther mal a nd moi s tu r e r e sponse o f bu i l d in gs . t o t a l o f
e igh t wal l sys tems, thr ee f rame wal l types and f iv e
c onc r e t e b loc k w a l l t ype s a r e under t e s t a t t he FSEC
Pass ive Cooling Labo rato ry (PCL) in Cape Canave ral.
Moi stu re s t ud i e s i nvo lve e xamina t ion o f t he
a bsor p t i on and de so r p t i on r a t e s o f bu i l d ing ma te r i a l s
and furn is hin gs and th e develop n~ent f improved moi stu re
migr at i on model l ing t e c hn iques f o r i nc lus ion i n bu i l d ing
energy an al ys is programs. TARP (Thermal An aly sis
Research program), d eveloped a t NBS by George Walton,
and FLOAD, by FCHART Sof tw ar e, ha ve bee n cho se n a s t h e
ana lys is programs wi th which cool in g
examined.
a l t e r n at i v e s a r e
The PCL
: s
c a pa b l e o f t h e p r e c i se p r oduct i o
both sen s ib le and la te nt energy. Any reason
in t e r i o r c ond i t i on ca n be p roduce d. Bo th t h e d r y
and dewpoint tempera tures can be sep ara te l y c on t ro
and maintained by computer . The l at en t and se n
energy requi red to produce and mainta in thos e con di
c a n be p r e c i se ly monito re d . F igur e
1
s h o w s a t e s t
load-measurement schemat ic i l lu s t ra t i n g th e load
measurement syrtems.
The s t r a t e g y employed f o r most t e s t s c on s i s t
s ide-by-s ide te s t in g (Figu re 2) in which the per form
of one component or te s t space i s compared wi th anot
One component i s u s u a l l y s t an d ar d t h ro u gh o u t t h e
pe r iod . T h i s s e r ve s a s a c on t r o l f o r t he e va lua t i o
th e le ss s tandard o r experimental compo
Reference
1
c on t a ins mor e de t a i l e d i n f o r ma t ion on
PCL.
Cur re n t t , z s t i ng c ompr ise s two t e s t c e l l s l oc a t e
t h e r e s t s i d e o f t h e PCL. B ot h c e l l s a r e eq u ip p e
shorn i n F igur e 1 fo r moi s tur e and thermal tes t in g.
c e l l ( c e l l D) c on t a ins wood f r a me e x t e r i o r w a l l sys
w h il e t h e o t h e r ( c e l l E c on t a ins c onc r e t e b
e x t e r i o r w a l l sy st em s. I n a l l , e i g h t d i f f e r e n t
sy stems a r e u ~ d e r e s t -- t hr e e wood frame s yst ems
f i ve c onc r e t e b lock sys t ems ( 1 ) .
Anal yt ic a l s tu die e a t FSEC are conduc ted u s in
va r i e t y of solytware . De ta i led an a l ys is of the rmal
s a s s t r a n s f e r p ro bl em s a r e c on du ct ed w i t h e i t h e r f i
d i f fe ren ce o r i i n i t e e lement programs which have
deve loped in-house t o mee t the s pe c i f i c needs of
work ( 2 ) . I c a dd i t i o n , two bu i l d ing e ner gy a na l
programs a re be ing used fo r parametr ic b ui l
a n a l y s i s . A l a r ge - sc a l e c onduc t ion t r a ns f e r f un
cod e ca ll ed TARP (Thermal An aly sis Research Program)
i s b ei n g us ed f o r d e t a i l e d a n a l y s i s and
a
microcom
based bin-method progra m c a l l e d FIOAD 4 ) i s be ing
PSEC has cl
and experimenta
hot, humid c 1
~
conducted in thc . . .. .. . - L a
b u il d in g o f r e s i d e n t i a l s c a l e j
cool ing and energy conserva t i on
be experimentall y ev alua ted unde
f u l l - s c a l e c o n d i t i o n s .
in w h i c h v a r i ou s p a ss i ve f o r o t h e r s t u d i e s .
bui l din g techniques can
, r c los e ly c on t r o l l e d bu t N e i the r
o
t h e s e
r n m e
n ~ n i n r ~ o r l
t n
bu i ld in g e ner gy- a na ly s i s c
.
I c or r e c t l y a na lyz e moi s t
ESL-HH-84-08-05
Proceedings of the First Symposium on Improving Building Systems in Hot and Humid Climates, August 1984
8/18/2019 07 ESL-HH-84-08-05
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Y A I I condlllonar
Lnral ooa c onduollva load
InllllrlH on load
O
Lalant lntarnal~oad
O. Smdbl a lnlarnal load
Vanlllallon load
Figure 1. Passive Cooling Laboratory (PCL)
Measurement, lo ads and Energy Balance
Schema t i c .
Expanded polystyrene (Li")
R
19
Fiber g lass ba t t
Ex ter io r nusmi te ( 7 /16 /" )
,-Vapar barrier
~ m d d
o l ys tv r en e ~ l i " ) E x t e ri o r m s o n i t e (:/lbm')
i
ai r soace . vented
,-muble sid ed bu il de r' s
Foil
.
io r maon ice ( ? /16 /" )
a i r space , ven ted
i pypslnn
d v w a l l
f o i l f aced r soc) nur a te [ S / 4 ]
D M
IRRIER WALL
ID
Environmental
Envlronmenl
95
=pQ=e0
Cofl'rol
b Chamber
Figure 2 . Se ct io n thru PCL Showing Environmental
Contr ol Chambers and Side-by- Side Te st in g
Strategy.
w e l y s t y r e n e (1 )
Ply*ood
bat ton (1 x 1;)
Exter ior masmite (7/16") 36 l b c o n cr e te b l x k
p o l ys t y re n e ( l j " ) ~ V a p c r a r r i e r
I
x
4
softwood
trun
E 2
xma 1NsJUTIcN
ded polystwene ( I")
1 si e t u l l d e r ' a f o l l
Exrerror mrsonite ['/lb
6 l b concre te b l d
-1
4
sof- trim
\ L i o n c r e t e m r t a r
E xp an de d p c l y s ~ v e n c
1 )
Foi l faced i sc- zmunts
W 4 )
G x e r i o r wasonice (7116~')
hrsmca W 4 v ' 1
fhmd b a r t m
{3/4
x I")
Eight Wall Syetems
Under
Teet
i n FSEC PCL.
23
ESL-HH-84-08-05
Proceedings of the First Symposium on Improving Building Systems in Hot and Humid Climates, August 1984
8/18/2019 07 ESL-HH-84-08-05
http://slidepdf.com/reader/full/07-esl-hh-84-08-05 3/7
Therefore , a major e f f or t i s underway a t FSEC t o develop
moisture migrat ion alg orith ms f or i ncl usi on i n TARP, and
th e FSEC ver si on of TARP now has de ta i le d .mo is tur e
n lod el l i n g cap a l i . l i t i e s . For ce r t a i n ma te r i a l s (mo st ly
newer s y n t h e t i c s ) , h owever, t h e r e i s l i t t l e o r no
mois ture proper ty data and absorp t ion , d i f f us io n and
desorp t ion parameters ar e no t yet wel l es tab l i shed .
SELECTED RESULTS
EXTERIOR WALL TESTS
Eight ex te r i or wal l sys tems have been under t e s t in
th e PCL sin ce September 1983. Fiv e of t he se wa ll
systems are equipped with rad ian t ba r r ie r sys tems . A
r ad ian t b a r r i e r s y st em co mp r is e s an a i r s p ac e wi th on e o r
more of i t s b ou n d ar i e s f u n c t io n in g a s a r a d ian t b a r r i e r
( low emi ss ivi ty su rf ac e) . For the PCL t e s t s , aluminum
fo i l i s u sed a s th e r ad ian t b a r r i e r s u r f ace . Two o f th e
r ad ian t b a r r i e r s y st ems a r e ap p l i ed t o wood f rame wa l l s
and th r ee a r e ap p l i ed to co n c re te b lock wa l l s . Fo r th e
b lo ck wa l l s y st ems , two r ad ian t b a r r i e r s a r e lo ca ted a t
the e x t er io r boundary of th e wal l and one
i s
l o c at e d a t
the in te r i or boundary of the wal l . Figure 3 shows a
plan view of ea ch wa ll system.
Measurements
Extensive measurements a re t aken f or each wall
system. A t
e
niinimum, t he s ur fa ce boundary t emper ature s
o f each ma te r i a l i n th e co mpo s it e s ec t io n a r e t aken .
For concre te b lock sys tems the a i r cor e temperature i s
al so measured wi th a rad ia t io n sh ie lded probe. In
ad d i t io n , f lu x meas uremen ts a r e t aken a t t h e i n t e r io r
sur fac e boundary of each wa ll system. Complete ex te ri or
me tero log ical d a ta a l s o a r e t ak en , in c lu d in g s o la r
in s o la t io n meas uremen ts o n a v e r t i ca l p l an e p a r a l l e l t o
th e ex te r n a l s u r f ace o f th e wa l l s ys tems .
A l l measurements ar e taken a t a 15-second scan
in t erv al , then averaged and recorded t o n ine- t rack tape
a t 1 5 -min ute r eco rd ing in t e r v a l s .
A
c on c er t ed e f f o r t i s
made t o u s e o n ly th e f in ea t q u a l i ty p rob es an d d a t a
acqui s i t i on sys tems , and a l l se ns i t iv e measurement
in s t ru ment s a r e c a l i b r a t ed ag a in s t NBS t r aceab le
r e f e r en ce s t an d a rds on a r eg u la r b as i s . Hea t f lu x
meter s a r e ca l ib r a t ed by in dep en den t t e s t i n g
lab ora tor ies a t temperatures 80°F) and f luxe s 2
~ t u / f t ~ +r ) l i k e ly t o be ex pe r i en ced in t e s t in g .
C o nd u c tiv i ty co r r ec t i o n f ac to r s th a t accou n t f o r
differences between meter and mounting material
c o n d u c ~ i v i t i e s r e a pp l i ed t o t h e i r o u t p ut s 51 .
Analvs is
Data ana lys is takes many forms ; t he u l t im ate
obj ect ive of each form
i s
t o p ro vi d e s i m p l i f i ed r e s u l t s
t h a t
m y
b e ap p l i ed in th e f i e l d . S in ce R -v alues a r e
mos t o f t en us ed in t h e f i e ld , an a t t emp t i s made h e r e t o
transpose the peak seasona
1
p er fo rman ce ch a rac te r i s t i c s
of rad i an t ba r r ie r sys tems to t he i r apparent R-values .
For th e p urp os e o f in - s i tu t e s t in g and an a ly s i s , o n ly
peak condi t ions dur ing which heat f low i s p r i mar i l y
undir ecti onnl may be used f or such an analy sis .
The gener a l form of th e equat ions used i n t he
an a ly s i s i s der ived f rom the s teady- s ta t e heat f low
equation
where Ra Apparen t R-value
E A T
=
Sum of th e measured tempe ratur e
d i f f e r e n t i a l s a c r os s
t1 e
Composite
Z =
Sum of th e measured hea t f lu xe s
a t
t h e i n t e r io r s u r f ac e b ou nd ary
I t i s impor tan t t o no te t ha t t he summations in
1
must be cont inuou s and cov er a period of t
s u f f i c i e n t ly lo n g t o mask th e t ime co n s tan t o f th e w
system ( 6 ) .
Three weather per iods were chosen for the an alys
One was a summer condition and two were win
con dit ion s. Dux ing t he gummer cond it io n and one of
w i n t e r c o n d i t i o r ~ s h e e x t e r i o r r a d i a n t b a r r i e r s ys t
were vented wit h ambient a ir . During the remain
win te r co n d i t io n v en t s were s ea led t o ev a lu a te u n ven
r a d i a n t b a r r i e r s ys te ms .
B ecau se o f v a r i a t io n s in wa l l co n s t ru c t io n f
wal l sys tem t o wal l sys tem th e AT term in Eq 1 v ar
drama t ica l ly f rom wal l sys tem to wa l l sys t
Therefore , apparent re a is tan ces were normal ized t
s t an d a rd wa l l co n s t ru c t io n . A base-case cons t ruct
was ch os en fo r each t e s t ce l l and th e wa l l s co n ta in
rad ian t ba r r i er sys tems were compared t o i t For
wood f r ame t e s t ce l l , w a l l D l was chosen as the ba
Fo r th e co n c re te b lo ck t e s t ce l l , wa l l E.1 was u s ed
th e base fo r wal l E .5 , and E.2 was used as the base
wa l ls E.3 and
E 4
( s e e F i g u r e 3 ) .
The c al cu ls te d base -cas e compoa i t e ASRRAE R-val
were then used with measured hea t f lu xe s to determ
t h e no rm al iz ed r e s i s t a n c e of t h e r a d i a n t b a r r i e r w
s y stems wi th r e s p ec t t o th e n on - rad ian t b a r r
base-case wal ls .
R es u l t s
Table
1
g l-ves th e r e s u l t s o f wa l l t e s t an a ly s
Although D.2 and E.3 have es se nt i al ly th e s
re f l ec t i ve vent .ed a i r spa ces th e i r summert ime R-va
a r e ra d i ca l l y d i f f er en t , R-9.7 and R-5.7 respe ct ive
Th i s i a p ro b ab ly du e to th e b as e r e s i e t an ce o f
r ema in d er o f th e wa l l s ec t io n . The e f f e c t of a r ad i
b a r r i e r i s t o n e ar l y e l i m i n a te th e s o l -a i r e f f e
Thu s, r ad ia n t b a r r i e r R -v alues t end t o b e h ig h e r
w a l l s w i t h hi g h l e v e l s o f o r d i n a r y i n s u l a t i o n . I t a
i l l u s t r a t e 6 t he f a c t t h a t r e f l e c t i v e a i r s p ac e e r e f l
hea t, so they cannot be well cha rac ter ize d by an R-va
alth ough R-value f or a vented 314 w a l l
i s
5.3 (w
E.4 as opposed t o 5.7 for the
1
1 / 2 w a l l ( ~ . 3 ) .
s ea led r ad ian t b a r r i e r wa l l (E.5) h as an
R
of 4 9 but
i s
on th e in s id e of th e wal l .
The performance of vented rad ian t b ar r i er s i s p
i n w i n t e r .
D :Z
yie lded an R of 0 .2 whi le t he dou
rad ian t ba r r ie r in D.3 had 5.7. In D.3 t he out s
r e f l e c t i v e a i r s p a c e was ve nt e d and t h e i n n e r r e f l e c t
a i r s p ace was b.ept s ea led fo r a l l t e s t s . The o u
vented ra d ia n t b ar r i er showed no re a l v a lue i n wal l D
The aea led r ad ia n t b a r r i e r R-va lu e ap p ea r s to b e s im
f o r D.3 and E 5 a t R-5.7 in win ter . Wall E.3 approac
th e same v a lu e when i t s ex te r io r v en t s a r e s ea led
win te r . The v en ted r ad ia n t b a r r i e r s in E 3 and
performed bet te r i n summer but worse i n win ter than
E.5.
Because of warm weat her, th e cloned-vent da ta
was co l lec ted f or on ly two days . Clos ing th e ven ts
improve performance. The be t t e r R-value fo r
ESL-HH-84-08-05
Proceedings of the First Symposium on Improving Building Systems in Hot and Humid Climates, August 1984
8/18/2019 07 ESL-HH-84-08-05
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T a b l e 1
V en te d a nd S e a l e d R a d i a n t B a r r i e r W a l l D a ta
Fl.UX RATIO BASE
T e s t d a y s
=
S e p t . 17 - 2 0, 1 9 8 3
A ve ra ge h ig li =8 8. 0 A ve ra ge 1 0 ~ ~ 7 5 . 8
H ea t f l u x i n t o s p a c e , B t u
ASHRAE R - v a l u e w / o r e f l . s p a c e
e l
F lu x r a t i o w r t b a s e c a s e
R -v al ue o f o v e r a l l w a l l
R - v a l ue o f r e f l e c t i v e s p a c e ( s )
T e s t D a ys J a n . 1 0 - 1 2 , 1 9 8 4
A v e r a g e h i g h = 7 2 , 7 A v e r a g e I o w= 6 6. 4
H ea t f l u x o u t , B tu
ASHRE R - v a l ue w / o r e f l . a p a c e ( s )
F lu x r a t i o w r t b a s e c a s e
R -v sl ue o f wh o l e w a l l w r t b a s e c a s e
R -va lu e o f r e f l e c t i v e s p a c e
6 )
T e a t D a y s = Feb. 7-8 1 9 8 4
A v e r a ge h i g h z 6 2 . 9 A v e r a g e l o w= 4 3. 5
H ea t f l u x o u t , B t u
ASHRXE R - v a l u e w / o r e f l . a p a c e ( 8 )
F lu x r a t i o w r t b a s e c a s e
R -v al u e o f wh o le w a l l w r t b a s e c a s e
R-va l u e o f r e f l e c t i v e s p a c e ( s )
---FRAME WALLS--- MASS WALLS
D
D.2 D.3 E l E. 2 E . 3 E . 4 E . 5
D 1 D l E.2 E.2 E. l
A
SUMMER VENTS OPEN ( E x c e p t E .5 )
Av. C e l l T em p. = n / a Av. C e l l T e mp . =7 7 .1
1 1 5 1 0 6 1 1 1 2 0 5 1 9 1 1 9 7 1 2 4 1 3
2 0 . 4 1 2 . 4 6 . 6 6 8 . 4 8 . 4 2 . 4 7 . 7 7 . 7
0 . 9 3 0 . 9 6 1 . 0 3 0 . 6 5 0 , 6
2 0 . 4 2 2 . 0 2 1 . 2 8 . 4 8 . 4 8 . 2 1 2 . 9 1 2 .
9 . 7 1 4 . 5 5 . 7 5 . 3 4 . 9
B WINTER VENTS OPEN ( ~ x c e p t . 5 )
A v. C e l l T e m p .= 7 2 . 4 Av. c e l l T e mp . =7 2 .1
1 3 2 2 1 6 2 0 0 3 1 5 3 4 6 5 6 2 2 8 9 1 9
2 0 . 3 1 2 . 3 6 . 5 8 , 3 8 . 3 2 . 3
7 6
7 .
1 6 3 1 66 1 . 6 2 0 . 8 4 0 . 6
20 3
1 2 . 5 1 2 . 2 8 . 3 8 . 3 5 . 1 1 0 . 1 1 3 .
0 . 2 5 . 7 2 . 8 2 .4
5 7
C ) WINTER VENTS CLOSED
Av . C e l l T e m p . =7 1 . 2 Av. C e l l T e m p . 17 0 . 4
5 9 9 6 9 8 1 2 6 1 2 4 2 3 9 1 1 3 8
2 0 . 3 1 2 . 3 6 . 5 8 . 3 8 . 3 2 . 3 7 . 6 7 .
1 . 3 6 1 . 5 5 1 . 1 5 0 . 8 0 0 . 6
2 0 . 3 1 5 . 0 1 3. 1 8 3 8 . 3 7 . 2 1 0 . 4 1 3 .
2 .7 6 . 5 4 . 9 2 . 8 6 . 3
re f l ec t i ve space in E.3 compared to th at i n E.4 i s
apparen t ly due t o the base r es i s t a nce o f the r emainder
of th e wa ll , th e aame phenomenon which ap pa re nt ly caused
t he di ff er en ce s between D.2 and E.3 and
D 3
and
E.4
i n
summer, but appl ied i n the oppos i te d ir ect ion . For
summert ime, i f the R-value f or the in te r i or ref le ct iv e
ai rs pa ce of wa ll E.5 (4.9) i s added t o th e ASHRAE
R-value fo r s o l id pa r t s of wal l D.3, the r es u l t an t
I t-va lue fo r t he ex t e r i o r ven ted r ad ian t ba r r i e r a i r epace
, 3
become8 9.7, id en ti ca l t o th at of wal l D.2. This
procedure can be appl ied t o wal l D.3 fo r each of
three cases (winter open and winter c losed) ,
i c ing ne t R-va lues fo r the ex t e r i o r r ad i an t ba r r i e r
, ac e t h a t a r e v e r y c l o s e t o t h o se g i v en i n w a ll
D 2
5
observat ions e tand out :
The performance of vented ex te r i or radi ant ba rr ie r
eystems i s po or i n t h e w i nt e r s e as on f o r a l l w a l l
types bu t i s pa r t i c u la r ly poor fo r f r ame wal l
systems.
The performance of exter ior radiant barr ier ays tems
in summer appears t o be re l a t ed t o the base wal l
res is t anc e and type. Frame wal ls appear t o ben ef i t
more f rom exter ior radiant barr iers than do mass
walls .
The perfonnance of in te r i or ra dia nt bar r i er sys tems
does not appear t o be very s t ro ngl y dependent on
ei ther season or wal l type.
lURE STUDIES
A s
s e n s i b l e c oo l i ng l o a d s a r e d ec r e ae e d , t h e l a t e n t
on buildings takes on increasing importance.
Cooling load analys is of a typ ica l F lo r ida r es idenc
l o c a t e d i n v ar i o ue F l o r i d a c l i m a t e s
i s
i n d i c a t i v e of t h
p roblem s tha t a r e f aced in such c l im at es . F igure
graphical ly depicts a breakdown of cool ing loads of
t y p i c a l f ra me w a l l r e s i d e n c e l o c a t e d i n t h r e e F l o r i d
c i t i e s .
Ce rt ai n key po in ts become appar ent i n examining t h
re s u l t s . F i r s t and ve ry im por tan t . i n te rna l loads an
in f i l t r a t i on accoun t fo r more than 50 of tbe to ta
load. More than ha lf of th i s
s
a mois ture load
Neither of these loade can be gr ea t l y reduced throug
bui ld i ng des ign. The i n f i l t ra t i o n load may be reduce
from .J5
ACH
to .5
A C H
bu t in te rna l ga ins p robab l
cannot be reduced witho ut ser i ous l i f e- s t y l e changes .
Therefore , in terms o f building des ign and hea
gai n prevent ion, we may only af fe ct 50 of th e to ta
load . Large s av ings in ex te rna l ly d r iven s ens ib le load
can probably be obta ined through s t r a t eg ic windo
s hading and r ad ia n t ba r r i e r e t r a te g ie s . Overa l l , we ca
reduce these external loads by half .
Another ser io us cool ing problem i s caused by t h
high mois ture loads in such cl ima tes . Each of the thr e
cl i mate s produces a moieture load grea te r than 30 o
th e t o t al load. However, a s sen s i bl e loads ar e reduce
through improved bui ld i ng pra ct i ces , the load s t ru ct ur
changes drama tic al l y because mois ture Ioads cannot b
s imultaneous ly reduced by curr en t l y ava i la bl
t echn iques . I f the ex t e rn a l l y d r iven loads ( s o l a r an
conduct ion) i n the re s idenc es analyzed ar e reduced b
ha lf , t he mois ture load becomes gr ea te r than 40 of t h
t o t a l l o a d .
Addi tio nal FSEC st ud ie s
7 )
have examined thi
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m
w i t h r e s p e c t t o a i r - c o n d i t i o n e r p e rf o rm a n ce .
,how s u r p r i s i n g r e s u l t s . As t h e l oa d s t r u c t u r e o n
, u i l d i n g c h o ng e s , c o m m e r ci a l l y a v a i l a b l e v a p o r
: s s i o n m e c ha n ic a l u n i t s b ecom e i n e f f e c t i v e i n
kg k i t h m o i s tu r e l o a d e . F i g u r e s
5
an d 6 i l l u s t r a t e
I f e c t o f s u ch c h a n g e s . T h r e e r e s i d e n c e t y p e s an d
x h a n i c a l u n i t e f f i c i e n c i e s a r e c om pa re d i n f i g u r e
he
h o u s e t y p e s a r e g i v e n a s : C O N -c o n ve n ti o na l ,
)L.
e n e t g y u s e , a nd PA S-v ery e n e r g y e f f i c i e n t .
~ i c a l y s t em a a r e g i v e n a s TA C -t yp ic al (S EE R 8 . 0 )
\ C - h i e l ) e f f i c i e n c y (SEER 11.0 . T he l i n e s p l o t e d
[ I
i n t e r i o r t a l ~ n c e o i n t a i r c o n d i t i o n s r ea ch ed
n e s t r a d y - s t a t e m a c h i ne p e r fo r m a n c e
t
t ~
s t
i c s .
Two
n~e
o r o b s e r v a t i o n s m ay b e dr a wn
igure 5.
6 a i r - c o n d i t o n e r e f f i c i e n c y i n c r e a s e s , t h e a b i l i t y
: o r e m o v e m o i s t u r e d e c r e a s e s .
\ s t h e t h er m a l p r o t e c t i o n
of
t h e b u i l d i n g e n v e l o p e
improves,
t h e i n d o o r b a l a n c e p o i n t r e l a t i v e
w m i d i t y r i s e s .
JACKSONVILLE
(Hay-Sap t )
OIUANLhJ
(Hay-Oct)
T ot al h a d 3 1 . 6 mBtu
Total load 4 3 . 0 d t u
Latent
33 . 7
t o t a l
Lacmc 31X t o t a l
M I M I
(Apr-Oct)
Tocal load 5 3 . 3 cu
Latent
35.2:
t o t a l
F i g u r e
4.
C o o l in g S e a so n Lo ad S t r u c t u r e s f o r a T y p i c a l
1 5 0 0 s q . f t . F ra me R e s i d e n c e L o c a te d i n T h r e e
F l o r i d a C i t i e s .
F i g u r e
6
i l l u s t r a t e s t h e r a t h e r s e v e r e p ro bl em a
f a c ed b y v e r y e ne r gy e f f i c i e n t r e s i d e n c e s w h er e b a l a n c e
p o i n t c o n d i t i o n s may r e m a i n a b o ve
70
r e l a t i v e h u m id i ty .
T h i s l e v e l
i s
u n a c c e p t a b l e i n r e s i d e n c e s b e c a u se o f t h e
p o t e n t i a l f o r mo ld a nd m i ld e w g ro w t h
8 ) .
A l t e r n a t i v e
l a t e n t c o o l i n g s y s t e m s w i l l b e r e q u i r e d f o r s u c h
r e s i d e n c e s .
T h i s p r o b l e m i s c om po un de d e v e n f u r t h e r w he n
p a s s i v e c o o l i n g t e c h n i q u e s a r e i n t r o d u c e d . C u r r e n t
r e s e a r c h i n d i c a t e s t h a t p a s s i v e c o o l i n g t e c h n iq u e s a r e
c a p a b l e o f s t a t i s f y i n g m os t o f t h e s e n s i b l e b u i l d i n g
C O N T A C
7 5 0 0
9
I N D O O R O R Y BULB OE
I N D OO R R H V S I N D O O R T f M P C R A T
F i g u r e 5.
I n t e r i o r B a l a n c e P o i n t R e1 a t v ~ umid
R ea ,z he d b y S i x B u i l d i n g r A i r C o n d i t i
C o m b i n a t i o n s i n M i am i , F L f o r V a r
T h e r m o st a t S e t t i n g s .
0 5 0
A C . P H
0 . 7 5 A C P H
1 . 0 0 A C P H
1
. S O
A C P H
7 5 9
e
5
I N O O D R O R Y B U L B O E O F
I N O C I O R R E L
H U M I O I T Y
V S OB
T E M P
F i g u r e 6. I n t e r i o r B a l an c e P o in t R e l a t i v e H u m i d
R e a ch e d by V e ry E n e r g y E f f i c i e n t H o us e
H ig h E f f i c i e n c y
A i r
C o n d i t i o n e r i n M ia m i
f o r V a r i o u s T h e r m os t a t S e t t i n g s
I n f i l t r a t i o n R a t es .
l o a d . I f c a r r i e d t o t h e e x tr e m e , n i g h t s k y r a d i
r o o f p on d s y s t em s l o c a t e d i n F l o r i d a c a n c o n
m o i s t u r e on t 'h e c e i l i n g p l a n e a nd r a i n o n t h e b u i
i n t e r i o r
9 ) .
O t h e r t e c h n i q u es s u c h a s n i g h t
v e n t i l a t i o n mrly i n t r o d u c e m or e m o i s t u r e l o a d t h a n
s e n s i b l e c o o l in g p o t e n t i a l w a r r a n t s . I n v e s t i g a t i o
t h i s p ro bl e m i s d i f f i c u l t b e c a u s e c u r r e n t b u i
e n e r gy a n a l y s i s t e ch n i q u e s m od el m o i s t u r e t r a n s p o
a n e x t r e m e l y ~ : u d im e n t ar y f a s h i o n a t b e s t .
M o is tu re Model-
A n a l y z i n l ~ m o i s t u r e i n b u i l d i n g s i s a c o
p ro b l em . C u r r e n t p r a c t i c e i n b u i l d i n g e n e rg y a n a
m o de la a ss u m es t h a t a l l c h an g e s i n z o ne h u m i d i t
r e f l e c t e d i n t h e z on e a i r c o n d i t i o n s , I n r e
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nt s and fu rn is hi ng s may absor b and
o ~ou nt s o f mo i stu r e. I n ad d i t io n ,
ten1 performance ch ar ac te r i s t ic s ,
s en s ib le h ea t f r ac t io n (SHR), a r e q u i t e
zone humidity.
veloped
a
d e ta i l ed mo is tu r e mo d e l l in g
I ~ U L ~b ~ a p n t l e f a cc ou nt in g f o r t he m i g ra t i on ,
n , and d es o rp t io n of mo i s tu r e in r ea l
The model has been wel l va l ida ted a gai ns t
2 ) and con~pared aga ins t measured con dit ion s
f u l l - s c a l e a t t i c s w i th good r e s u l t s . F i g u r e 7 g i v e s
re s ul ts of FSEC's
MADAM
( I I o i ~ t u r e A b so rp t io n
~ o d e l ) p rogram and measurements
by Cleary (101. The agreement i s ex ce ll en t. This
s p r i ma r i ly d ue t o t h e d e t a i l e d c a p a b i l i t y of t h e MADAM
A co rr el at io n between ext er na l wind speed was
ed in th e mod el t o o b ta i n an in t e rn a l s u r f ac e
is
h ig h ly d ep en d ent ) . Witho ut th i s co r r e l a t i o n
eement i s not a s good.
I
. .
Ambient Dew Po in t
easured A t t i c Dew Po in t
.
ADAM Pred ic t ed
AcC. icDew Po in t
I U
ter Code P re di ct ion
Eta from Ful l-S cal e
o v i l l e ,
CA
f o r March
i l e d f i n i t e el em en t
have a l lowed us t o
accura te model ing
mois ture parameters
s l y s i s .
Design day TARP runs f or Orlando, Fl or id a, have
been made with the FSE mo is tu r e a lg o r i th m i n p lace .
The an a ly e i s t ech n iq u e u t i l i z ed a h y p o th e t i ca l
mechanical sys tem capable of main ta in ing zone mois ture
c o n d i ti o n s a t 60 RH The mechanic al s ystem was run
with a 30-minute on cy cl e dur ing each hour. Resul ts
f rom the run ar e shown i n Figu re
8.
The s o l i d l i n e i n
th e f ig u re g iv es th e in s t an tan eo u s mo is tu r e lo ad on t li e
s p ace a s s u n in g n o mo is tu r e ab s o rp t io n and d e s o rp t io n .
The dashed l in e giv es t he load assuming th e same
mechanical sys tem and wit h mois ture asorp t ion and
d es o rp t io n by th e b u i ld i n g ma te r i a l s ( d ry wa ll i n t h i s
case ) . The do ts g iven in the f ig ur e show the mechanical
sys tem SHF required t o main ta in these condi t ions .
ithauc M D M
nth W
6 =
load
6 . + .
h
Figure 8.
TARP
Analys is of Laten t Load Predic t ions
with and wi thout Absorp t ion Desorp t ion
Mod e l .
I t i s q u i t e i n t e r e s t i n g t o no t e t h a t a s i g n i f ic a n t
d i f fe re nc e ex is ts be tween th e loads when absorp t ion and
d e s o r p t io n a r e m od el le d. T h i e i s e s p e c i a l l y t r u e f o r
th e p eak co n d i t io n . t i s a l s o i n t e r e s ti n g t o no te t h e
la r g e SHF v a r i an ce t h a t i s r eq u i r ed to ma in ta in th i s 6 0%
RH The r e s u l t s a r e g iv en fo r t h e f in a l d ay o f a 5-day
r un a t d e s i gn c o n d i t i o n s
(db hig h 93OF, db lo v = 77OF,
coi nci den t wb = 760F, c learness =
. 95 ) .
Th e d a i ly
mo is tu r e lo ads on th e b u i ld in g a r e s t i l l u n equ a l by a
s ma l l amo un t a t t h e end of t h i s p e r io d , i n d ica t in g th a t
the mois tur e t ime cons tan t o f a bu i ld i ng may be ra t he r
l a r g e a s comp ared t o t h e th e rma l t ime co n s tan t .
CONCLUSIONS
FSEC has concluded from i t s s t u d i e s t h a t m o i s tu r e
p ro blems i n b u i ld in g s l o ca ted in h o t , humid c l ima te s a r e
q u i t e s i g n i f i c a n t . The inc lus ion of mois ture a lgor i thms
in TARP has shown ma te ri al ab sor pti on and des orp tio n t o
b e a v e ry s i g n i f i c a n t e f f e c t t h a t
i s
n o t c u r r e n t l y
co n s id e red in b u i ld i n g en e rgy an a l y s i s cod es .
Very energy ef Ei ci en t and pas siv ely coaled
s t ru ct ur es may su f f er unacceptab l e mois ture problems
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mhanced d eh u mid if i ca t io n cap ab i l i t i e s . C e r t a in
cool ing s t ra te g i es (n i ght vent ing) may pay a
penal ty th a t exceeds th e thermal cool ing
in very humid clim etes . In ord er t o understand
luate these problems
i t i s
imp o r tan t th a t
rese arch cont inue and tha t bu i ld ing energy
cod cs co r r ec t ly an a ly ze mo istu r e e f f e c t s .
ACKNOWLEDGMENTS
autho rs would l ik e t o thank th e Gae Research
i n genera l end Doug Kosar i n par t ic u l ar fo r
pport of much of th e work reported in t h i s
Addi t ional agencies which have contr i bu ted to
inp of t he work inclu de the Flor ida Div is i on o f
Affairs and NASA/Kennedy Space Center.
REFERENCES
rey
P.
"Passive Cool i n g f ~ a s Technology
ra ct er iz at io n and Development Work Plan ," Gas
l s r ch In s t i t u t e , C hicago , I l i n o i s , ( J u ne 19 83 ).
:ey,
P.
"Pa ss ive Cooling/Gas Techno1 ogy
rac ter iza t io n and Development Qua r te r ly
x t
Nov. '83 Ja n '84," Gas Res ear ch
& , , =i i t ut e , Chicago, I l l i n o i s , ( ~ e b r u e r ~9841.
3. Walton, G.
TARP Re fer enc e Manual, NBSIR 83-2655,
Nati onrl Bureau of S tnn dsr ds, Washington, DC,
() arch 198 3).
4. FLOAD, A Building and Equiment Enerav
se
Analveis
Program, FCHART Sof twa re, M idd let on, W is con sin ,
(1984).
5. Bligh , T. "Heat Flux Meter Correction Factors ,"
Fi na l Report, MIT, Cambridge, MA (Ap ril 28, 1983).
6.
Fair ey, P. "Effe cts
O F
In Era r ed R ad ia t io n B ar r i e r s
on th e Eff ec ti ve Thermal Performance of Bu ildi ng
Envelopes
.
Proceedings of ASHRAE~DOEonference
on Thermal Performance
of
Exterior Envelopes of
Buildings
I T b s
Vegas, NV,(December 1982).
7.
Khat tar ,
M
and Swami,
M.
"Impact of Passive
Cool ing Stra teg ies on A i r Conditioner Performance
in Warm, Humid Clim ates ." ASME So la r Energy
Div isi on Si xth Annual Techn ical ConEerence, Las
Vegaa, NV (Apr i l 1984) .
8. Humphreys, W.E., "Co nde ns ati on and Remedial
Measures I' Condeneation i n Build inas , Edit ed
y
Derek, Groome and Sh er ra tt , Applied S cien ce
Pub lis her s Ltd., London (1932).
9 . P i e i r a ,
R.K.
Enernv Savinas Pote n t i a l o f
Pehumidif ied Roof Pond Reside nces , Th es is f o r M.S.
in Applied Solar Energy, Tr in it y Unive rsit y, San
Antonio, TEXAS, (1983).
10 . C lery , Pe te r , p e r s o n a l co n v e r s at io n and l e t t e r
da te d 10 Hay 1984.
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