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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


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

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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

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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 )


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 )


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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